Makefile

@@ -1,22 +1,22 @@
 
 CONFIG = ./config.nix
-BASH = $$(nix-build --no-out-link -A pkgs.bash)/bin/bash
 
 entrypoint:
-	nix-build -A entrypoint --arg config '(import ${CONFIG})'
+	nix-build -A entrypoint \
+		--arg baseConfig '(import ${CONFIG})'
 
-install-systemd:
+install:
-	$$(nix-build --no-out-link -A install --arg config '(import ${CONFIG})')
+	$$(nix-build -A install --arg baseConfig '(import ${CONFIG})')
 
 test:
-	${BASH} tmp-dev-env.sh \
+	$$(nix-build --no-out-link -A pkgs.bash)/bin/bash srv-dev-env.sh \
-    	--run "cd src; go test ./... -count=1 -tags integration"
+    	--run "cd srv/src && go test ./... -count=1 -tags integration"
+	@echo "\nTESTS PASSED!\n"
 
-shell:
+srv.dev-shell:
-	${BASH} tmp-dev-env.sh \
+	$$(nix-build --no-out-link -A pkgs.bash)/bin/bash srv-dev-env.sh \
-		--command " \
+		--command "cd srv/src; return"
-			cd src; \
+
-          	echo 'Loading test data...'; \
+srv.shell:
-          	(cd cmd/load-test-data && go run main.go); \
+	nix-shell -A srv.shellWithBuild --arg baseConfig '(import ${CONFIG})' \
-			return; \
+		--command 'cd srv/src; return'
-		"

default.nix

@@ -1,69 +1,78 @@
 {
 
-    pkgs ? import (fetchTarball {
+    pkgsArg ? import (fetchTarball {
         name = "nixpkgs-21-05";
         url = "https://github.com/NixOS/nixpkgs/archive/7e9b0dff974c89e070da1ad85713ff3c20b0ca97.tar.gz";
         sha256 = "1ckzhh24mgz6jd1xhfgx0i9mijk6xjqxwsshnvq789xsavrmsc36";
     }) {},
 
-    config ? import ./config.nix,
+    baseConfig ? import ./config.nix,
+    skipServices ? [],
 
 }: rec {
 
-    inherit pkgs;
+    pkgs = pkgsArg;
 
-    init = pkgs.writeText "mediocre-blog-init" ''
+    config = baseConfig // {
+        redisListenPath = "${config.runDir}/redis";
+    };
 
-      export MEDIOCRE_BLOG_DATA_DIR="${config.dataDir}"
+    srv = pkgs.callPackage (import ./srv) {
+        inherit config;
+    };
 
-      # mailing list
+    redisCfg = pkgs.writeText "mediocre-blog-redisCfg" ''
-      export MEDIOCRE_BLOG_ML_SMTP_ADDR="${config.mlSMTPAddr}"
+        port 0
-      export MEDIOCRE_BLOG_ML_SMTP_AUTH="${config.mlSMTPAuth}"
+        unixsocket ${config.redisListenPath}
-      export MEDIOCRE_BLOG_ML_PUBLIC_URL="${config.publicURL}"
+        daemonize no
-
+        loglevel notice
-      # pow
+        logfile ""
-      export MEDIOCRE_BLOG_POW_SECRET="${config.powSecret}"
+        appendonly yes
-
+        appendfilename "appendonly.aof"
-      # http
+        dir ${config.dataDir}/redis
-      export MEDIOCRE_BLOG_HTTP_PUBLIC_URL="${config.publicURL}"
-      export MEDIOCRE_BLOG_HTTP_LISTEN_PROTO="${config.httpListenProto}"
-      export MEDIOCRE_BLOG_HTTP_LISTEN_ADDR="${config.httpListenAddr}"
-      export MEDIOCRE_BLOG_HTTP_AUTH_USERS='${builtins.toJSON config.httpAuthUsers}'
-      export MEDIOCRE_BLOG_HTTP_AUTH_RATELIMIT='${config.httpAuthRatelimit}'
     '';
 
-    bin = pkgs.buildGoModule {
+    redisBin = pkgs.writeScript "mediocre-blog-redisBin" ''
-        pname = "mediocre-blog";
+        #!/bin/sh
-        version = "dev";
+        mkdir -p ${config.dataDir}/redis
-        src = ./src;
+        exec ${pkgs.redis}/bin/redis-server ${redisCfg}
-        vendorSha256 = "sha256:1vazrrg8rs9n8x40c9r53h9qnyxw59xkp0aq7jl15fliigk6q0cr";
+    '';
 
-        subPackages = [ "cmd/mediocre-blog" ];
+    srvCircusCfg = ''
+        [watcher:srv]
+        cmd = ${srv.bin}
+        numprocesses = 1
+    '';
 
-        # disable tests
+    redisCircusCfg = ''
-        checkPhase = '''';
+        [watcher:redis]
-    };
+        cmd = ${redisBin}
+        numprocesses = 1
+    '';
+
+    circusCfg = pkgs.writeText "mediocre-blog-circusCfg" ''
+        [circus]
+        endpoint = tcp://127.0.0.1:0
+        pubsub_endpoint = tcp://127.0.0.1:0
+
+        ${if (!builtins.elem "srv" skipServices) then srvCircusCfg else ""}
+
+        ${if (!builtins.elem "redis" skipServices) then redisCircusCfg else ""}
+    '';
 
     entrypoint = pkgs.writeScript "mediocre-blog-entrypoint" ''
-        #!${pkgs.bash}/bin/bash
+        #!/bin/sh
 
         set -e
-        source ${init}
 
+        if [ ! -d ${config.runDir} ]; then
           mkdir -p ${config.runDir}
+        fi
+
         mkdir -p ${config.dataDir}
-
+        exec ${pkgs.circus}/bin/circusd ${circusCfg}
-        exec ${bin}/bin/mediocre-blog "$@"
     '';
 
-    shell = pkgs.stdenv.mkDerivation {
-        name = "mediocre-blog-shell";
-        buildInputs = [ pkgs.go pkgs.sqlite ];
-        shellHook = ''
-          source ${init}
-        '';
-    };
-
     service = pkgs.writeText "mediocre-blog" ''
         [Unit]
         Description=mediocregopher mediocre blog

srv-dev-env.sh

@@ -0,0 +1,29 @@
+
+test_dir="$(mktemp -d)"
+
+mkdir -p "$test_dir"/run
+mkdir -p "$test_dir"/data
+
+test_cfg="(import ./config.nix) // {
+    runDir=\"${test_dir}/run\";
+    dataDir=\"${test_dir}/data\";
+}"
+
+entrypoint=$(nix-build --no-out-link -A entrypoint \
+    --arg baseConfig "$test_cfg" \
+    --arg skipServices '["srv"]')
+
+$entrypoint &
+trap "kill $!; wait; rm -rf $test_dir" EXIT
+
+# NOTE this is a bit of a hack... the location of the redis socket's source of
+# truth is in default.nix, but it's not clear how to get that from there to
+# here, so we reproduce the calculation here.
+while [ ! -e $test_dir/run/redis ]; do
+    echo "waiting for redis unix socket"
+    sleep 1
+done
+
+nix-shell -A srv.shell \
+    --arg baseConfig "$test_cfg" \
+    "$@"

srv/default.nix

@@ -0,0 +1,63 @@
+{
+  bash,
+  go,
+  buildGoModule,
+  sqlite,
+  writeScript,
+  writeText,
+  stdenv,
+
+  config,
+}: rec {
+
+    init = writeText "mediocre-blog-srv-init" ''
+
+      export MEDIOCRE_BLOG_DATA_DIR="${config.dataDir}"
+
+      # mailing list
+      export MEDIOCRE_BLOG_ML_SMTP_ADDR="${config.mlSMTPAddr}"
+      export MEDIOCRE_BLOG_ML_SMTP_AUTH="${config.mlSMTPAuth}"
+      export MEDIOCRE_BLOG_ML_PUBLIC_URL="${config.publicURL}"
+
+      # redis
+      export MEDIOCRE_BLOG_REDIS_PROTO=unix
+      export MEDIOCRE_BLOG_REDIS_ADDR="${config.redisListenPath}"
+
+      # pow
+      export MEDIOCRE_BLOG_POW_SECRET="${config.powSecret}"
+
+      # http
+      export MEDIOCRE_BLOG_HTTP_PUBLIC_URL="${config.publicURL}"
+      export MEDIOCRE_BLOG_HTTP_LISTEN_PROTO="${config.httpListenProto}"
+      export MEDIOCRE_BLOG_HTTP_LISTEN_ADDR="${config.httpListenAddr}"
+      export MEDIOCRE_BLOG_HTTP_AUTH_USERS='${builtins.toJSON config.httpAuthUsers}'
+      export MEDIOCRE_BLOG_HTTP_AUTH_RATELIMIT='${config.httpAuthRatelimit}'
+    '';
+
+    build = buildGoModule {
+        pname = "mediocre-blog-srv";
+        version = "dev";
+        src = ./src;
+        vendorSha256 = "sha256-C3hyPDO+6oTUeoGP/ZzBn5Y4V/q1jI12BwkR9NADHn0=";
+
+        # disable tests
+        checkPhase = '''';
+    };
+
+    bin = writeScript "mediocre-blog-srv-bin" ''
+        #!${bash}/bin/bash
+        source ${init}
+        exec ${build}/bin/mediocre-blog
+    '';
+
+    shell = stdenv.mkDerivation {
+        name = "mediocre-blog-srv-shell";
+        buildInputs = [ go sqlite ];
+        shellHook = ''
+          source ${init}
+
+          echo "Loading test data..."
+          (cd srv/src/cmd/load-test-data && go run main.go)
+        '';
+    };
+}

srv/src/cfg/radix_client.go

@@ -0,0 +1,55 @@
+package cfg
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/mediocregopher/mediocre-go-lib/v2/mctx"
+	"github.com/mediocregopher/radix/v4"
+)
+
+// RadixClient is a single redis client which can be configured.
+type RadixClient struct {
+	radix.Client
+
+	proto, addr string
+	poolSize    int
+}
+
+// SetupCfg implement the cfg.Cfger interface.
+func (c *RadixClient) SetupCfg(cfg *Cfg) {
+
+	cfg.StringVar(&c.proto, "redis-proto", "tcp", "Network protocol to connect to redis over, can be tcp or unix")
+	cfg.StringVar(&c.addr, "redis-addr", "127.0.0.1:6379", "Address redis is expected to listen on")
+	cfg.IntVar(&c.poolSize, "redis-pool-size", 5, "Number of connections in the redis pool to keep")
+
+	cfg.OnInit(func(ctx context.Context) error {
+		client, err := (radix.PoolConfig{
+			Size: c.poolSize,
+		}).New(
+			ctx, c.proto, c.addr,
+		)
+
+		if err != nil {
+			return fmt.Errorf(
+				"initializing redis pool of size %d at %s://%s: %w",
+				c.poolSize, c.proto, c.addr, err,
+			)
+		}
+
+		c.Client = client
+		return nil
+	})
+}
+
+// Annotate implements mctx.Annotator interface.
+func (c *RadixClient) Annotate(a mctx.Annotations) {
+	a["redisProto"] = c.proto
+	a["redisAddr"] = c.addr
+	a["redisPoolSize"] = c.poolSize
+}
+
+// Close cleans up the radix client.
+func (c *RadixClient) Close() error {
+	return c.Client.Close()
+}

srv/src/chat/chat.go

@@ -0,0 +1,467 @@
+// Package chat implements a simple chatroom system.
+package chat
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"strconv"
+	"sync"
+	"time"
+
+	"github.com/mediocregopher/mediocre-go-lib/v2/mctx"
+	"github.com/mediocregopher/mediocre-go-lib/v2/mlog"
+	"github.com/mediocregopher/radix/v4"
+)
+
+// ErrInvalidArg is returned from methods in this package when a call fails due
+// to invalid input.
+type ErrInvalidArg struct {
+	Err error
+}
+
+func (e ErrInvalidArg) Error() string {
+	return fmt.Sprintf("invalid argument: %v", e.Err)
+}
+
+var (
+	errInvalidMessageID = ErrInvalidArg{Err: errors.New("invalid Message ID")}
+)
+
+// Message describes a message which has been posted to a Room.
+type Message struct {
+	ID        string `json:"id"`
+	UserID    UserID `json:"userID"`
+	Body      string `json:"body"`
+	CreatedAt int64  `json:"createdAt,omitempty"`
+}
+
+func msgFromStreamEntry(entry radix.StreamEntry) (Message, error) {
+
+	// NOTE this should probably be a shortcut in radix
+	var bodyStr string
+	for _, field := range entry.Fields {
+		if field[0] == "json" {
+			bodyStr = field[1]
+			break
+		}
+	}
+
+	if bodyStr == "" {
+		return Message{}, errors.New("no 'json' field")
+	}
+
+	var msg Message
+	if err := json.Unmarshal([]byte(bodyStr), &msg); err != nil {
+		return Message{}, fmt.Errorf(
+			"json unmarshaling body %q: %w", bodyStr, err,
+		)
+	}
+
+	msg.ID = entry.ID.String()
+	msg.CreatedAt = int64(entry.ID.Time / 1000)
+	return msg, nil
+}
+
+// MessageIterator returns a sequence of Messages which may or may not be
+// unbounded.
+type MessageIterator interface {
+
+	// Next blocks until it returns the next Message in the sequence, or the
+	// context error if the context is cancelled, or io.EOF if the sequence has
+	// been exhausted.
+	Next(context.Context) (Message, error)
+
+	// Close should always be called once Next has returned an error or the
+	// MessageIterator will no longer be used.
+	Close() error
+}
+
+// HistoryOpts are passed into Room's History method in order to affect its
+// result. All fields are optional.
+type HistoryOpts struct {
+	Limit  int    // defaults to, and is capped at, 100.
+	Cursor string // If not given then the most recent Messages are returned.
+}
+
+func (o HistoryOpts) sanitize() (HistoryOpts, error) {
+	if o.Limit <= 0 || o.Limit > 100 {
+		o.Limit = 100
+	}
+
+	if o.Cursor != "" {
+		id, err := parseStreamEntryID(o.Cursor)
+		if err != nil {
+			return HistoryOpts{}, fmt.Errorf("parsing Cursor: %w", err)
+		}
+		o.Cursor = id.String()
+	}
+
+	return o, nil
+}
+
+// Room implements functionality related to a single, unique chat room.
+type Room interface {
+
+	// Append accepts a new Message and stores it at the end of the room's
+	// history. The original Message is returned with any relevant fields (e.g.
+	// ID) updated.
+	Append(context.Context, Message) (Message, error)
+
+	// Returns a cursor and the list of historical Messages in time descending
+	// order. The cursor can be passed into the next call to History to receive
+	// the next set of Messages.
+	History(context.Context, HistoryOpts) (string, []Message, error)
+
+	// Listen returns a MessageIterator which will return all Messages appended
+	// to the Room since the given ID. Once all existing messages are iterated
+	// through then the MessageIterator will begin blocking until a new Message
+	// is posted.
+	Listen(ctx context.Context, sinceID string) (MessageIterator, error)
+
+	// Delete deletes a Message from the Room.
+	Delete(ctx context.Context, id string) error
+
+	// Close is used to clean up all resources created by the Room.
+	Close() error
+}
+
+// RoomParams are used to instantiate a new Room. All fields are required unless
+// otherwise noted.
+type RoomParams struct {
+	Logger      *mlog.Logger
+	Redis       radix.Client
+	ID          string
+	MaxMessages int
+}
+
+func (p RoomParams) streamKey() string {
+	return fmt.Sprintf("chat:{%s}:stream", p.ID)
+}
+
+type room struct {
+	params RoomParams
+
+	closeCtx    context.Context
+	closeCancel context.CancelFunc
+	wg          sync.WaitGroup
+
+	listeningL      sync.Mutex
+	listening       map[chan Message]struct{}
+	listeningLastID radix.StreamEntryID
+}
+
+// NewRoom initializes and returns a new Room instance.
+func NewRoom(ctx context.Context, params RoomParams) (Room, error) {
+
+	params.Logger = params.Logger.WithNamespace("chat-room")
+
+	r := &room{
+		params:    params,
+		listening: map[chan Message]struct{}{},
+	}
+
+	r.closeCtx, r.closeCancel = context.WithCancel(context.Background())
+
+	// figure out the most recent message, if any.
+	lastEntryID, err := r.mostRecentMsgID(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("discovering most recent entry ID in stream: %w", err)
+	}
+	r.listeningLastID = lastEntryID
+
+	r.wg.Add(1)
+	go func() {
+		defer r.wg.Done()
+		r.readStreamLoop(r.closeCtx)
+	}()
+
+	return r, nil
+}
+
+func (r *room) Close() error {
+	r.closeCancel()
+	r.wg.Wait()
+	return nil
+}
+
+func (r *room) mostRecentMsgID(ctx context.Context) (radix.StreamEntryID, error) {
+
+	var entries []radix.StreamEntry
+	err := r.params.Redis.Do(ctx, radix.Cmd(
+		&entries,
+		"XREVRANGE", r.params.streamKey(), "+", "-", "COUNT", "1",
+	))
+
+	if err != nil || len(entries) == 0 {
+		return radix.StreamEntryID{}, err
+	}
+
+	return entries[0].ID, nil
+}
+
+func (r *room) Append(ctx context.Context, msg Message) (Message, error) {
+	msg.ID = "" // just in case
+
+	b, err := json.Marshal(msg)
+	if err != nil {
+		return Message{}, fmt.Errorf("json marshaling Message: %w", err)
+	}
+
+	key := r.params.streamKey()
+	maxLen := strconv.Itoa(r.params.MaxMessages)
+	body := string(b)
+
+	var id radix.StreamEntryID
+
+	err = r.params.Redis.Do(ctx, radix.Cmd(
+		&id, "XADD", key, "MAXLEN", "=", maxLen, "*", "json", body,
+	))
+
+	if err != nil {
+		return Message{}, fmt.Errorf("posting message to redis: %w", err)
+	}
+
+	msg.ID = id.String()
+	msg.CreatedAt = int64(id.Time / 1000)
+	return msg, nil
+}
+
+const zeroCursor = "0-0"
+
+func (r *room) History(ctx context.Context, opts HistoryOpts) (string, []Message, error) {
+	opts, err := opts.sanitize()
+	if err != nil {
+		return "", nil, err
+	}
+
+	key := r.params.streamKey()
+	end := opts.Cursor
+	if end == "" {
+		end = "+"
+	}
+	start := "-"
+	count := strconv.Itoa(opts.Limit)
+
+	msgs := make([]Message, 0, opts.Limit)
+	streamEntries := make([]radix.StreamEntry, 0, opts.Limit)
+
+	err = r.params.Redis.Do(ctx, radix.Cmd(
+		&streamEntries,
+		"XREVRANGE", key, end, start, "COUNT", count,
+	))
+
+	if err != nil {
+		return "", nil, fmt.Errorf("calling XREVRANGE: %w", err)
+	}
+
+	var oldestEntryID radix.StreamEntryID
+
+	for _, entry := range streamEntries {
+		oldestEntryID = entry.ID
+
+		msg, err := msgFromStreamEntry(entry)
+		if err != nil {
+			return "", nil, fmt.Errorf(
+				"parsing stream entry %q: %w", entry.ID, err,
+			)
+		}
+		msgs = append(msgs, msg)
+	}
+
+	if len(msgs) < opts.Limit {
+		return zeroCursor, msgs, nil
+	}
+
+	cursor := oldestEntryID.Prev()
+	return cursor.String(), msgs, nil
+}
+
+func (r *room) readStream(ctx context.Context) error {
+
+	r.listeningL.Lock()
+	lastEntryID := r.listeningLastID
+	r.listeningL.Unlock()
+
+	redisAddr := r.params.Redis.Addr()
+	redisConn, err := radix.Dial(ctx, redisAddr.Network(), redisAddr.String())
+	if err != nil {
+		return fmt.Errorf("creating redis connection: %w", err)
+	}
+	defer redisConn.Close()
+
+	streamReader := (radix.StreamReaderConfig{}).New(
+		redisConn,
+		map[string]radix.StreamConfig{
+			r.params.streamKey(): {After: lastEntryID},
+		},
+	)
+
+	for {
+		dlCtx, dlCtxCancel := context.WithTimeout(ctx, 10*time.Second)
+		_, streamEntry, err := streamReader.Next(dlCtx)
+		dlCtxCancel()
+
+		if errors.Is(err, radix.ErrNoStreamEntries) {
+			continue
+		} else if err != nil {
+			return fmt.Errorf("fetching next entry from stream: %w", err)
+		}
+
+		msg, err := msgFromStreamEntry(streamEntry)
+		if err != nil {
+			return fmt.Errorf("parsing stream entry %q: %w", streamEntry, err)
+		}
+
+		r.listeningL.Lock()
+
+		var dropped int
+		for ch := range r.listening {
+			select {
+			case ch <- msg:
+			default:
+				dropped++
+			}
+		}
+
+		if dropped > 0 {
+			ctx := mctx.Annotate(ctx, "msgID", msg.ID, "dropped", dropped)
+			r.params.Logger.WarnString(ctx, "some listening channels full, messages dropped")
+		}
+
+		r.listeningLastID = streamEntry.ID
+
+		r.listeningL.Unlock()
+	}
+}
+
+func (r *room) readStreamLoop(ctx context.Context) {
+	for {
+		err := r.readStream(ctx)
+		if errors.Is(err, context.Canceled) {
+			return
+		} else if err != nil {
+			r.params.Logger.Error(ctx, "reading from redis stream", err)
+		}
+	}
+}
+
+type listenMsgIterator struct {
+	ch           <-chan Message
+	missedMsgs   []Message
+	sinceEntryID radix.StreamEntryID
+	cleanup      func()
+}
+
+func (i *listenMsgIterator) Next(ctx context.Context) (Message, error) {
+
+	if len(i.missedMsgs) > 0 {
+		msg := i.missedMsgs[0]
+		i.missedMsgs = i.missedMsgs[1:]
+		return msg, nil
+	}
+
+	for {
+		select {
+		case <-ctx.Done():
+			return Message{}, ctx.Err()
+		case msg := <-i.ch:
+
+			entryID, err := parseStreamEntryID(msg.ID)
+			if err != nil {
+				return Message{}, fmt.Errorf("parsing Message ID %q: %w", msg.ID, err)
+
+			} else if !i.sinceEntryID.Before(entryID) {
+				// this can happen if someone Appends a Message at the same time
+				// as another calls Listen. The Listener might have already seen
+				// the Message by calling History prior to the stream reader
+				// having processed it and updating listeningLastID.
+				continue
+			}
+
+			return msg, nil
+		}
+	}
+}
+
+func (i *listenMsgIterator) Close() error {
+	i.cleanup()
+	return nil
+}
+
+func (r *room) Listen(
+	ctx context.Context, sinceID string,
+) (
+	MessageIterator, error,
+) {
+
+	var sinceEntryID radix.StreamEntryID
+
+	if sinceID != "" {
+		var err error
+		if sinceEntryID, err = parseStreamEntryID(sinceID); err != nil {
+			return nil, fmt.Errorf("parsing sinceID: %w", err)
+		}
+	}
+
+	ch := make(chan Message, 32)
+
+	r.listeningL.Lock()
+	lastEntryID := r.listeningLastID
+	r.listening[ch] = struct{}{}
+	r.listeningL.Unlock()
+
+	cleanup := func() {
+		r.listeningL.Lock()
+		defer r.listeningL.Unlock()
+		delete(r.listening, ch)
+	}
+
+	key := r.params.streamKey()
+	start := sinceEntryID.Next().String()
+	end := "+"
+	if lastEntryID != (radix.StreamEntryID{}) {
+		end = lastEntryID.String()
+	}
+
+	var streamEntries []radix.StreamEntry
+
+	err := r.params.Redis.Do(ctx, radix.Cmd(
+		&streamEntries,
+		"XRANGE", key, start, end,
+	))
+
+	if err != nil {
+		cleanup()
+		return nil, fmt.Errorf("retrieving missed stream entries: %w", err)
+	}
+
+	missedMsgs := make([]Message, len(streamEntries))
+
+	for i := range streamEntries {
+
+		msg, err := msgFromStreamEntry(streamEntries[i])
+		if err != nil {
+			cleanup()
+			return nil, fmt.Errorf(
+				"parsing stream entry %q: %w", streamEntries[i].ID, err,
+			)
+		}
+
+		missedMsgs[i] = msg
+	}
+
+	return &listenMsgIterator{
+		ch:           ch,
+		missedMsgs:   missedMsgs,
+		sinceEntryID: sinceEntryID,
+		cleanup:      cleanup,
+	}, nil
+}
+
+func (r *room) Delete(ctx context.Context, id string) error {
+	return r.params.Redis.Do(ctx, radix.Cmd(
+		nil, "XDEL", r.params.streamKey(), id,
+	))
+}

srv/src/chat/chat_it_test.go

@@ -0,0 +1,213 @@
+//go:build integration
+// +build integration
+
+package chat
+
+import (
+	"context"
+	"strconv"
+	"testing"
+	"time"
+
+	"github.com/google/uuid"
+	cfgpkg "github.com/mediocregopher/blog.mediocregopher.com/srv/cfg"
+	"github.com/mediocregopher/mediocre-go-lib/v2/mlog"
+	"github.com/mediocregopher/radix/v4"
+	"github.com/stretchr/testify/assert"
+)
+
+const roomTestHarnessMaxMsgs = 10
+
+type roomTestHarness struct {
+	ctx     context.Context
+	room    Room
+	allMsgs []Message
+}
+
+func (h *roomTestHarness) newMsg(t *testing.T) Message {
+	msg, err := h.room.Append(h.ctx, Message{
+		UserID: UserID{
+			Name: uuid.New().String(),
+			Hash: "0000",
+		},
+		Body: uuid.New().String(),
+	})
+	assert.NoError(t, err)
+
+	t.Logf("appended message %s", msg.ID)
+
+	h.allMsgs = append([]Message{msg}, h.allMsgs...)
+
+	if len(h.allMsgs) > roomTestHarnessMaxMsgs {
+		h.allMsgs = h.allMsgs[:roomTestHarnessMaxMsgs]
+	}
+
+	return msg
+}
+
+func newRoomTestHarness(t *testing.T) *roomTestHarness {
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	t.Cleanup(cancel)
+
+	cfg := cfgpkg.NewBlogCfg(cfgpkg.Params{
+		Args: []string{}, // prevents the test process args from interfering
+	})
+
+	var radixClient cfgpkg.RadixClient
+	radixClient.SetupCfg(cfg)
+	t.Cleanup(func() { radixClient.Close() })
+
+	if err := cfg.Init(ctx); err != nil {
+		t.Fatal(err)
+	}
+
+	roomParams := RoomParams{
+		Logger:      mlog.NewLogger(nil),
+		Redis:       radixClient.Client,
+		ID:          uuid.New().String(),
+		MaxMessages: roomTestHarnessMaxMsgs,
+	}
+
+	t.Logf("creating test Room %q", roomParams.ID)
+	room, err := NewRoom(ctx, roomParams)
+	assert.NoError(t, err)
+
+	t.Cleanup(func() {
+		err := radixClient.Client.Do(context.Background(), radix.Cmd(
+			nil, "DEL", roomParams.streamKey(),
+		))
+		assert.NoError(t, err)
+	})
+
+	return &roomTestHarness{ctx: ctx, room: room}
+}
+
+func TestRoom(t *testing.T) {
+	t.Run("history", func(t *testing.T) {
+
+		tests := []struct {
+			numMsgs int
+			limit   int
+		}{
+			{numMsgs: 0, limit: 1},
+			{numMsgs: 1, limit: 1},
+			{numMsgs: 2, limit: 1},
+			{numMsgs: 2, limit: 10},
+			{numMsgs: 9, limit: 2},
+			{numMsgs: 9, limit: 3},
+			{numMsgs: 9, limit: 4},
+			{numMsgs: 15, limit: 3},
+		}
+
+		for i, test := range tests {
+			t.Run(strconv.Itoa(i), func(t *testing.T) {
+				t.Logf("test: %+v", test)
+
+				h := newRoomTestHarness(t)
+
+				for j := 0; j < test.numMsgs; j++ {
+					h.newMsg(t)
+				}
+
+				var gotMsgs []Message
+				var cursor string
+
+				for {
+
+					var msgs []Message
+					var err error
+					cursor, msgs, err = h.room.History(h.ctx, HistoryOpts{
+						Cursor: cursor,
+						Limit:  test.limit,
+					})
+
+					assert.NoError(t, err)
+					assert.NotEmpty(t, cursor)
+
+					if len(msgs) == 0 {
+						break
+					}
+
+					gotMsgs = append(gotMsgs, msgs...)
+				}
+
+				assert.Equal(t, h.allMsgs, gotMsgs)
+			})
+		}
+	})
+
+	assertNextMsg := func(
+		t *testing.T, expMsg Message,
+		ctx context.Context, it MessageIterator,
+	) {
+		t.Helper()
+		gotMsg, err := it.Next(ctx)
+		assert.NoError(t, err)
+		assert.Equal(t, expMsg, gotMsg)
+	}
+
+	t.Run("listen/already_populated", func(t *testing.T) {
+		h := newRoomTestHarness(t)
+
+		msgA, msgB, msgC := h.newMsg(t), h.newMsg(t), h.newMsg(t)
+		_ = msgA
+		_ = msgB
+
+		itFoo, err := h.room.Listen(h.ctx, msgC.ID)
+		assert.NoError(t, err)
+		defer itFoo.Close()
+
+		itBar, err := h.room.Listen(h.ctx, msgA.ID)
+		assert.NoError(t, err)
+		defer itBar.Close()
+
+		msgD := h.newMsg(t)
+
+		// itBar should get msgB and msgC before anything else.
+		assertNextMsg(t, msgB, h.ctx, itBar)
+		assertNextMsg(t, msgC, h.ctx, itBar)
+
+		// now both iterators should give msgD
+		assertNextMsg(t, msgD, h.ctx, itFoo)
+		assertNextMsg(t, msgD, h.ctx, itBar)
+
+		// timeout should be honored
+		{
+			timeoutCtx, timeoutCancel := context.WithTimeout(h.ctx, 1*time.Second)
+			_, errFoo := itFoo.Next(timeoutCtx)
+			_, errBar := itBar.Next(timeoutCtx)
+			timeoutCancel()
+
+			assert.ErrorIs(t, errFoo, context.DeadlineExceeded)
+			assert.ErrorIs(t, errBar, context.DeadlineExceeded)
+		}
+
+		// new message should work
+		{
+			expMsg := h.newMsg(t)
+
+			timeoutCtx, timeoutCancel := context.WithTimeout(h.ctx, 1*time.Second)
+			gotFooMsg, errFoo := itFoo.Next(timeoutCtx)
+			gotBarMsg, errBar := itBar.Next(timeoutCtx)
+			timeoutCancel()
+
+			assert.Equal(t, expMsg, gotFooMsg)
+			assert.NoError(t, errFoo)
+			assert.Equal(t, expMsg, gotBarMsg)
+			assert.NoError(t, errBar)
+		}
+
+	})
+
+	t.Run("listen/empty", func(t *testing.T) {
+		h := newRoomTestHarness(t)
+
+		it, err := h.room.Listen(h.ctx, "")
+		assert.NoError(t, err)
+		defer it.Close()
+
+		msg := h.newMsg(t)
+		assertNextMsg(t, msg, h.ctx, it)
+	})
+}

srv/src/chat/user.go

@@ -0,0 +1,68 @@
+package chat
+
+import (
+	"encoding/hex"
+	"fmt"
+	"sync"
+
+	"golang.org/x/crypto/argon2"
+)
+
+// UserID uniquely identifies an individual user who has posted a message in a
+// Room.
+type UserID struct {
+
+	// Name will be the user's chosen display name.
+	Name string `json:"name"`
+
+	// Hash will be a hex string generated from a secret only the user knows.
+	Hash string `json:"id"`
+}
+
+// UserIDCalculator is used to calculate UserIDs.
+type UserIDCalculator struct {
+
+	// Secret is used when calculating UserID Hash salts.
+	Secret []byte
+
+	// TimeCost, MemoryCost, and Threads are used as inputs to the Argon2id
+	// algorithm which is used to generate the Hash.
+	TimeCost, MemoryCost uint32
+	Threads              uint8
+
+	// HashLen specifies the number of bytes the Hash should be.
+	HashLen uint32
+
+	// Lock, if set, forces concurrent Calculate calls to occur sequentially.
+	Lock *sync.Mutex
+}
+
+// NewUserIDCalculator returns a UserIDCalculator with sane defaults.
+func NewUserIDCalculator(secret []byte) *UserIDCalculator {
+	return &UserIDCalculator{
+		Secret:     secret,
+		TimeCost:   15,
+		MemoryCost: 128 * 1024,
+		Threads:    2,
+		HashLen:    16,
+		Lock:       new(sync.Mutex),
+	}
+}
+
+// Calculate accepts a name and password and returns the calculated UserID.
+func (c *UserIDCalculator) Calculate(name, password string) UserID {
+
+	input := fmt.Sprintf("%q:%q", name, password)
+
+	hashB := argon2.IDKey(
+		[]byte(input),
+		c.Secret, // salt
+		c.TimeCost, c.MemoryCost, c.Threads,
+		c.HashLen,
+	)
+
+	return UserID{
+		Name: name,
+		Hash: hex.EncodeToString(hashB),
+	}
+}

srv/src/chat/user_test.go

@@ -0,0 +1,26 @@
+package chat
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestUserIDCalculator(t *testing.T) {
+
+	const name, password = "name", "password"
+
+	c := NewUserIDCalculator([]byte("foo"))
+
+	// calculating with same params twice should result in same UserID
+	userID := c.Calculate(name, password)
+	assert.Equal(t, userID, c.Calculate(name, password))
+
+	// changing either name or password should result in a different Hash
+	assert.NotEqual(t, userID.Hash, c.Calculate(name+"!", password).Hash)
+	assert.NotEqual(t, userID.Hash, c.Calculate(name, password+"!").Hash)
+
+	// changing the secret should change the UserID
+	c.Secret = []byte("bar")
+	assert.NotEqual(t, userID, c.Calculate(name, password))
+}

srv/src/chat/util.go

@@ -0,0 +1,28 @@
+package chat
+
+import (
+	"strconv"
+	"strings"
+
+	"github.com/mediocregopher/radix/v4"
+)
+
+func parseStreamEntryID(str string) (radix.StreamEntryID, error) {
+
+	split := strings.SplitN(str, "-", 2)
+	if len(split) != 2 {
+		return radix.StreamEntryID{}, errInvalidMessageID
+	}
+
+	time, err := strconv.ParseUint(split[0], 10, 64)
+	if err != nil {
+		return radix.StreamEntryID{}, errInvalidMessageID
+	}
+
+	seq, err := strconv.ParseUint(split[1], 10, 64)
+	if err != nil {
+		return radix.StreamEntryID{}, errInvalidMessageID
+	}
+
+	return radix.StreamEntryID{Time: time, Seq: seq}, nil
+}

srv/src/cmd/mediocre-blog/main.go

@@ -8,6 +8,7 @@ import (
 	"time"
 
 	cfgpkg "github.com/mediocregopher/blog.mediocregopher.com/srv/cfg"
+	"github.com/mediocregopher/blog.mediocregopher.com/srv/chat"
 	"github.com/mediocregopher/blog.mediocregopher.com/srv/http"
 	"github.com/mediocregopher/blog.mediocregopher.com/srv/mailinglist"
 	"github.com/mediocregopher/blog.mediocregopher.com/srv/post"
@@ -44,6 +45,14 @@ func main() {
 	httpParams.SetupCfg(cfg)
 	ctx = mctx.WithAnnotator(ctx, &httpParams)
 
+	var radixClient cfgpkg.RadixClient
+	radixClient.SetupCfg(cfg)
+	defer radixClient.Close()
+	ctx = mctx.WithAnnotator(ctx, &radixClient)
+
+	chatGlobalRoomMaxMsgs := cfg.Int("chat-global-room-max-messages", 1000, "Maximum number of messages the global chat room can retain")
+	chatUserIDCalcSecret := cfg.String("chat-user-id-calc-secret", "", "Secret to use when calculating user ids")
+
 	// initialization
 	err := cfg.Init(ctx)
 
@@ -57,6 +66,10 @@ func main() {
 		logger.Fatal(ctx, "initializing", err)
 	}
 
+	ctx = mctx.Annotate(ctx,
+		"chatGlobalRoomMaxMsgs", *chatGlobalRoomMaxMsgs,
+	)
+
 	clock := clock.Realtime()
 
 	powStore := pow.NewMemoryStore(clock)
@@ -87,6 +100,19 @@ func main() {
 
 	ml := mailinglist.New(mlParams)
 
+	chatGlobalRoom, err := chat.NewRoom(ctx, chat.RoomParams{
+		Logger:      logger.WithNamespace("global-chat-room"),
+		Redis:       radixClient.Client,
+		ID:          "global",
+		MaxMessages: *chatGlobalRoomMaxMsgs,
+	})
+	if err != nil {
+		logger.Fatal(ctx, "initializing global chat room", err)
+	}
+	defer chatGlobalRoom.Close()
+
+	chatUserIDCalc := chat.NewUserIDCalculator([]byte(*chatUserIDCalcSecret))
+
 	postSQLDB, err := post.NewSQLDB(dataDir)
 	if err != nil {
 		logger.Fatal(ctx, "initializing sql db for post data", err)
@@ -103,6 +129,8 @@ func main() {
 	httpParams.PostAssetStore = postAssetStore
 	httpParams.PostDraftStore = postDraftStore
 	httpParams.MailingList = ml
+	httpParams.GlobalRoom = chatGlobalRoom
+	httpParams.UserIDCalculator = chatUserIDCalc
 
 	logger.Info(ctx, "listening")
 	httpAPI, err := http.New(httpParams)

srv/src/cmd/userid-calc-cli/main.go

@@ -0,0 +1,28 @@
+package main
+
+import (
+	"encoding/json"
+	"flag"
+	"fmt"
+
+	"github.com/mediocregopher/blog.mediocregopher.com/srv/chat"
+)
+
+func main() {
+
+	secret := flag.String("secret", "", "Secret to use when calculating UserIDs")
+	name := flag.String("name", "", "")
+	password := flag.String("password", "", "")
+
+	flag.Parse()
+
+	calc := chat.NewUserIDCalculator([]byte(*secret))
+	userID := calc.Calculate(*name, *password)
+
+	b, err := json.Marshal(userID)
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Println(string(b))
+}

srv/src/go.mod

@@ -3,14 +3,17 @@ module github.com/mediocregopher/blog.mediocregopher.com/srv
 go 1.16
 
 require (
+	github.com/adrg/frontmatter v0.2.0
 	github.com/emersion/go-sasl v0.0.0-20200509203442-7bfe0ed36a21
 	github.com/emersion/go-smtp v0.15.0
 	github.com/gomarkdown/markdown v0.0.0-20220510115730-2372b9aa33e5
 	github.com/google/uuid v1.3.0
-	github.com/gorilla/feeds v1.1.1
+	github.com/gorilla/feeds v1.1.1 // indirect
-	github.com/hashicorp/golang-lru v0.5.4
+	github.com/gorilla/websocket v1.4.2
+	github.com/hashicorp/golang-lru v0.5.4 // indirect
 	github.com/mattn/go-sqlite3 v1.14.8
 	github.com/mediocregopher/mediocre-go-lib/v2 v2.0.0-beta.0.0.20220506011745-cbeee71cb1ee
+	github.com/mediocregopher/radix/v4 v4.0.0-beta.1.0.20210726230805-d62fa1b2e3cb
 	github.com/rubenv/sql-migrate v0.0.0-20210614095031-55d5740dbbcc
 	github.com/stretchr/testify v1.7.0
 	github.com/tilinna/clock v1.1.0
@@ -19,5 +22,5 @@ require (
 	golang.org/x/image v0.0.0-20220413100746-70e8d0d3baa9
 	golang.org/x/sys v0.0.0-20211216021012-1d35b9e2eb4e // indirect
 	golang.org/x/term v0.0.0-20210927222741-03fcf44c2211 // indirect
-	gopkg.in/yaml.v3 v3.0.1
+	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

srv/src/go.sum

@@ -1,9 +1,12 @@
 cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
+github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/Masterminds/goutils v1.1.0/go.mod h1:8cTjp+g8YejhMuvIA5y2vz3BpJxksy863GQaJW2MFNU=
 github.com/Masterminds/semver v1.5.0/go.mod h1:MB6lktGJrhw8PrUyiEoblNEGEQ+RzHPF078ddwwvV3Y=
 github.com/Masterminds/sprig v2.22.0+incompatible/go.mod h1:y6hNFY5UBTIWBxnzTeuNhlNS5hqE0NB0E6fgfo2Br3o=
 github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAElWljhcU=
+github.com/adrg/frontmatter v0.2.0 h1:/DgnNe82o03riBd1S+ZDjd43wAmC6W35q67NHeLkPd4=
+github.com/adrg/frontmatter v0.2.0/go.mod h1:93rQCj3z3ZlwyxxpQioRKC1wDLto4aXHrbqIsnH9wmE=
 github.com/alecthomas/template v0.0.0-20160405071501-a0175ee3bccc/go.mod h1:LOuyumcjzFXgccqObfd/Ljyb9UuFJ6TxHnclSeseNhc=
 github.com/alecthomas/units v0.0.0-20151022065526-2efee857e7cf/go.mod h1:ybxpYRFXyAe+OPACYpWeL0wqObRcbAqCMya13uyzqw0=
 github.com/armon/consul-api v0.0.0-20180202201655-eb2c6b5be1b6/go.mod h1:grANhF5doyWs3UAsr3K4I6qtAmlQcZDesFNEHPZAzj8=
@@ -65,6 +68,8 @@ github.com/google/uuid v1.3.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+
 github.com/gorilla/feeds v1.1.1 h1:HwKXxqzcRNg9to+BbvJog4+f3s/xzvtZXICcQGutYfY=
 github.com/gorilla/feeds v1.1.1/go.mod h1:Nk0jZrvPFZX1OBe5NPiddPw7CfwF6Q9eqzaBbaightA=
 github.com/gorilla/websocket v1.4.0/go.mod h1:E7qHFY5m1UJ88s3WnNqhKjPHQ0heANvMoAMk2YaljkQ=
+github.com/gorilla/websocket v1.4.2 h1:+/TMaTYc4QFitKJxsQ7Yye35DkWvkdLcvGKqM+x0Ufc=
+github.com/gorilla/websocket v1.4.2/go.mod h1:YR8l580nyteQvAITg2hZ9XVh4b55+EU/adAjf1fMHhE=
 github.com/grpc-ecosystem/go-grpc-middleware v1.0.0/go.mod h1:FiyG127CGDf3tlThmgyCl78X/SZQqEOJBCDaAfeWzPs=
 github.com/grpc-ecosystem/go-grpc-prometheus v1.2.0/go.mod h1:8NvIoxWQoOIhqOTXgfV/d3M/q6VIi02HzZEHgUlZvzk=
 github.com/grpc-ecosystem/grpc-gateway v1.9.0/go.mod h1:vNeuVxBJEsws4ogUvrchl83t/GYV9WGTSLVdBhOQFDY=
@@ -112,6 +117,8 @@ github.com/mattn/go-sqlite3 v1.14.8/go.mod h1:NyWgC/yNuGj7Q9rpYnZvas74GogHl5/Z4A
 github.com/matttproud/golang_protobuf_extensions v1.0.1/go.mod h1:D8He9yQNgCq6Z5Ld7szi9bcBfOoFv/3dc6xSMkL2PC0=
 github.com/mediocregopher/mediocre-go-lib/v2 v2.0.0-beta.0.0.20220506011745-cbeee71cb1ee h1:AWRuhgn7iumyhPuxKwed1F1Ri2dXMwxKfp5YIdpnQIY=
 github.com/mediocregopher/mediocre-go-lib/v2 v2.0.0-beta.0.0.20220506011745-cbeee71cb1ee/go.mod h1:wOZVlnKYvIbkzyCJ3dxy1k40XkirvCd1pisX2O91qoQ=
+github.com/mediocregopher/radix/v4 v4.0.0-beta.1.0.20210726230805-d62fa1b2e3cb h1:7Y2vAC5q44VJzbBUdxRUEqfz88ySJ/6yXXkpQ+sxke4=
+github.com/mediocregopher/radix/v4 v4.0.0-beta.1.0.20210726230805-d62fa1b2e3cb/go.mod h1:ajchozX/6ELmydxWeWM6xCFHVpZ4+67LXHOTOVR0nCE=
 github.com/mitchellh/cli v1.1.2/go.mod h1:6iaV0fGdElS6dPBx0EApTxHrcWvmJphyh2n8YBLPPZ4=
 github.com/mitchellh/copystructure v1.0.0/go.mod h1:SNtv71yrdKgLRyLFxmLdkAbkKEFWgYaq1OVrnRcwhnw=
 github.com/mitchellh/go-homedir v1.1.0/go.mod h1:SfyaCUpYCn1Vlf4IUYiD9fPX4A5wJrkLzIz1N1q0pr0=
@@ -160,6 +167,7 @@ github.com/stretchr/testify v1.5.1/go.mod h1:5W2xD1RspED5o8YsWQXVCued0rvSQ+mT+I5
 github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/tilinna/clock v1.0.2/go.mod h1:ZsP7BcY7sEEz7ktc0IVy8Us6boDrK8VradlKRUGfOao=
 github.com/tilinna/clock v1.1.0 h1:6IQQQCo6KoBxVudv6gwtY8o4eDfhHo8ojA5dP0MfhSs=
 github.com/tilinna/clock v1.1.0/go.mod h1:ZsP7BcY7sEEz7ktc0IVy8Us6boDrK8VradlKRUGfOao=
 github.com/tmc/grpc-websocket-proxy v0.0.0-20190109142713-0ad062ec5ee5/go.mod h1:ncp9v5uamzpCO7NfCPTXjqaC+bZgJeR0sMTm6dMHP7U=
@@ -244,7 +252,9 @@ gopkg.in/yaml.v2 v2.0.0-20170812160011-eb3733d160e7/go.mod h1:JAlM8MvJe8wmxCU4Bl
 gopkg.in/yaml.v2 v2.2.1/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.3.0/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v2 v2.4.0 h1:D8xgwECY7CYvx+Y2n4sBz93Jn9JRvxdiyyo8CTfuKaY=
 gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

srv/src/http/api.go

@@ -17,6 +17,7 @@ import (
 
 	lru "github.com/hashicorp/golang-lru"
 	"github.com/mediocregopher/blog.mediocregopher.com/srv/cfg"
+	"github.com/mediocregopher/blog.mediocregopher.com/srv/chat"
 	"github.com/mediocregopher/blog.mediocregopher.com/srv/http/apiutil"
 	"github.com/mediocregopher/blog.mediocregopher.com/srv/mailinglist"
 	"github.com/mediocregopher/blog.mediocregopher.com/srv/post"
@@ -40,6 +41,9 @@ type Params struct {
 
 	MailingList mailinglist.MailingList
 
+	GlobalRoom       chat.Room
+	UserIDCalculator *chat.UserIDCalculator
+
 	// PublicURL is the base URL which site visitors can navigate to.
 	PublicURL *url.URL
 
@@ -172,9 +176,16 @@ func (a *api) apiHandler() http.Handler {
 	mux.Handle("/mailinglist/finalize", a.mailingListFinalizeHandler())
 	mux.Handle("/mailinglist/unsubscribe", a.mailingListUnsubscribeHandler())
 
-	return apiutil.MethodMux(map[string]http.Handler{
+	mux.Handle("/chat/global/", http.StripPrefix("/chat/global", newChatHandler(
-		"POST": mux,
+		a.params.GlobalRoom,
-	})
+		a.params.UserIDCalculator,
+		a.requirePowMiddleware,
+	)))
+
+	// disallowGetMiddleware is used rather than a MethodMux because it has an
+	// exception for websockets, which is needed for chat.
+	return disallowGetMiddleware(mux)
+
 }
 
 func (a *api) blogHandler() http.Handler {

srv/src/http/assets.go

@@ -155,7 +155,7 @@ func (a *api) postPostAssetHandler() http.Handler {
 	return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
 
 		id := r.PostFormValue("id")
-		if id == "" {
+		if id == "/" {
 			apiutil.BadRequest(rw, r, errors.New("id is required"))
 			return
 		}

srv/src/http/chat.go

@@ -0,0 +1,211 @@
+package http
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/http"
+	"strings"
+	"unicode"
+
+	"github.com/gorilla/websocket"
+	"github.com/mediocregopher/blog.mediocregopher.com/srv/chat"
+	"github.com/mediocregopher/blog.mediocregopher.com/srv/http/apiutil"
+)
+
+type chatHandler struct {
+	*http.ServeMux
+
+	room       chat.Room
+	userIDCalc *chat.UserIDCalculator
+
+	wsUpgrader websocket.Upgrader
+}
+
+func newChatHandler(
+	room chat.Room, userIDCalc *chat.UserIDCalculator,
+	requirePowMiddleware func(http.Handler) http.Handler,
+) http.Handler {
+	c := &chatHandler{
+		ServeMux:   http.NewServeMux(),
+		room:       room,
+		userIDCalc: userIDCalc,
+
+		wsUpgrader: websocket.Upgrader{},
+	}
+
+	c.Handle("/history", c.historyHandler())
+	c.Handle("/user-id", requirePowMiddleware(c.userIDHandler()))
+	c.Handle("/append", requirePowMiddleware(c.appendHandler()))
+	c.Handle("/listen", c.listenHandler())
+
+	return c
+}
+
+func (c *chatHandler) historyHandler() http.Handler {
+	return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
+		limit, err := apiutil.StrToInt(r.PostFormValue("limit"), 0)
+		if err != nil {
+			apiutil.BadRequest(rw, r, fmt.Errorf("invalid limit parameter: %w", err))
+			return
+		}
+
+		cursor := r.PostFormValue("cursor")
+
+		cursor, msgs, err := c.room.History(r.Context(), chat.HistoryOpts{
+			Limit:  limit,
+			Cursor: cursor,
+		})
+
+		if argErr := (chat.ErrInvalidArg{}); errors.As(err, &argErr) {
+			apiutil.BadRequest(rw, r, argErr.Err)
+			return
+		} else if err != nil {
+			apiutil.InternalServerError(rw, r, err)
+		}
+
+		apiutil.JSONResult(rw, r, struct {
+			Cursor   string         `json:"cursor"`
+			Messages []chat.Message `json:"messages"`
+		}{
+			Cursor:   cursor,
+			Messages: msgs,
+		})
+	})
+}
+
+func (c *chatHandler) userID(r *http.Request) (chat.UserID, error) {
+	name := r.PostFormValue("name")
+	if l := len(name); l == 0 {
+		return chat.UserID{}, errors.New("name is required")
+	} else if l > 16 {
+		return chat.UserID{}, errors.New("name too long")
+	}
+
+	nameClean := strings.Map(func(r rune) rune {
+		if !unicode.IsPrint(r) {
+			return -1
+		}
+		return r
+	}, name)
+
+	if nameClean != name {
+		return chat.UserID{}, errors.New("name contains invalid characters")
+	}
+
+	password := r.PostFormValue("password")
+	if l := len(password); l == 0 {
+		return chat.UserID{}, errors.New("password is required")
+	} else if l > 128 {
+		return chat.UserID{}, errors.New("password too long")
+	}
+
+	return c.userIDCalc.Calculate(name, password), nil
+}
+
+func (c *chatHandler) userIDHandler() http.Handler {
+	return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
+		userID, err := c.userID(r)
+		if err != nil {
+			apiutil.BadRequest(rw, r, err)
+			return
+		}
+
+		apiutil.JSONResult(rw, r, struct {
+			UserID chat.UserID `json:"userID"`
+		}{
+			UserID: userID,
+		})
+	})
+}
+
+func (c *chatHandler) appendHandler() http.Handler {
+	return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
+		userID, err := c.userID(r)
+		if err != nil {
+			apiutil.BadRequest(rw, r, err)
+			return
+		}
+
+		body := r.PostFormValue("body")
+
+		if l := len(body); l == 0 {
+			apiutil.BadRequest(rw, r, errors.New("body is required"))
+			return
+
+		} else if l > 300 {
+			apiutil.BadRequest(rw, r, errors.New("body too long"))
+			return
+		}
+
+		msg, err := c.room.Append(r.Context(), chat.Message{
+			UserID: userID,
+			Body:   body,
+		})
+
+		if err != nil {
+			apiutil.InternalServerError(rw, r, err)
+			return
+		}
+
+		apiutil.JSONResult(rw, r, struct {
+			MessageID string `json:"messageID"`
+		}{
+			MessageID: msg.ID,
+		})
+	})
+}
+
+func (c *chatHandler) listenHandler() http.Handler {
+	return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
+
+		ctx := r.Context()
+		sinceID := r.FormValue("sinceID")
+
+		conn, err := c.wsUpgrader.Upgrade(rw, r, nil)
+		if err != nil {
+			apiutil.BadRequest(rw, r, err)
+			return
+		}
+		defer conn.Close()
+
+		it, err := c.room.Listen(ctx, sinceID)
+
+		if errors.As(err, new(chat.ErrInvalidArg)) {
+			apiutil.BadRequest(rw, r, err)
+			return
+
+		} else if errors.Is(err, context.Canceled) {
+			return
+
+		} else if err != nil {
+			apiutil.InternalServerError(rw, r, err)
+			return
+		}
+
+		defer it.Close()
+
+		for {
+
+			msg, err := it.Next(ctx)
+			if errors.Is(err, context.Canceled) {
+				return
+
+			} else if err != nil {
+				apiutil.InternalServerError(rw, r, err)
+				return
+			}
+
+			err = conn.WriteJSON(struct {
+				Message chat.Message `json:"message"`
+			}{
+				Message: msg,
+			})
+
+			if err != nil {
+				apiutil.GetRequestLogger(r).Error(ctx, "couldn't write message", err)
+				return
+			}
+		}
+	})
+}