package garage

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/http/httputil"
	"net/netip"
	"time"

	"dev.mediocregopher.com/mediocre-go-lib.git/mctx"
	"dev.mediocregopher.com/mediocre-go-lib.git/mlog"
)

// BucketID is a unique identifier for a bucket in garage. It is different than
// the bucket's alias, since a bucket may have multiple aliases.
type BucketID string

// BucketPermission describes a permission an S3APICredentials may have when
// interacting with a bucket.
type BucketPermission string

// Enumeration of BucketPermissions.
const (
	BucketPermissionRead  BucketPermission = "read"
	BucketPermissionWrite BucketPermission = "write"
	BucketPermissionOwner BucketPermission = "owner"
)

// Bucket defines a bucket which has been created in a cluster
type Bucket struct {
	ID            BucketID `json:"id"`
	GlobalAliases []string `json:"globalAliases"`
}

// AdminClientError gets returned from AdminClient Do methods for non-200
// errors.
type AdminClientError struct {
	StatusCode int
	Body       []byte
}

func (e AdminClientError) Error() string {
	return fmt.Sprintf("%d response from admin: %q", e.StatusCode, e.Body)
}

// AdminClient is a helper type for performing actions against the garage admin
// interface.
type AdminClient struct {
	logger     *mlog.Logger
	c          *http.Client
	addr       string
	adminToken string

	transport *http.Transport
}

// NewAdminClient initializes and returns an AdminClient which will use the
// given address and adminToken for all requests made.
//
// If Logger is nil then logs will be suppressed.
func NewAdminClient(logger *mlog.Logger, addr, adminToken string) *AdminClient {
	transport := http.DefaultTransport.(*http.Transport).Clone()

	return &AdminClient{
		logger: logger,
		c: &http.Client{
			Transport: transport,
		},
		addr:       addr,
		adminToken: adminToken,
		transport:  transport,
	}
}

// Close cleans up all resources held by the lient.
func (c *AdminClient) Close() error {
	c.transport.CloseIdleConnections()
	return nil
}

// do performs an HTTP request with the given method (GET, POST) and path, and
// using the json marshaling of the given body as the request body (unless body
// is nil). It will JSON unmarshal the response into rcv, unless rcv is nil.
func (c *AdminClient) do(
	ctx context.Context, rcv any, method, path string, body any,
) error {

	var bodyR io.Reader

	if body != nil {
		bodyBuf := new(bytes.Buffer)
		bodyR = bodyBuf

		if err := json.NewEncoder(bodyBuf).Encode(body); err != nil {
			return fmt.Errorf("json marshaling body: %w", err)
		}
	}

	urlStr := fmt.Sprintf("http://%s%s", c.addr, path)

	req, err := http.NewRequestWithContext(ctx, method, urlStr, bodyR)
	if err != nil {
		return fmt.Errorf("initializing request: %w", err)
	}

	req.Header.Set("Authorization", "Bearer "+c.adminToken)

	if c.logger.MaxLevel() >= mlog.LevelDebug.Int() {

		reqB, err := httputil.DumpRequestOut(req, true)
		if err != nil {
			c.logger.Error(ctx, "failed to dump http request", err)
		} else {
			c.logger.Debug(ctx, "------ request ------\n"+string(reqB)+"\n")
		}
	}

	res, err := c.c.Do(req)
	if err != nil {
		return fmt.Errorf("performing http request: %w", err)
	}

	if c.logger.MaxLevel() >= mlog.LevelDebug.Int() {

		resB, err := httputil.DumpResponse(res, true)
		if err != nil {
			c.logger.Error(ctx, "failed to dump http response", err)
		} else {
			c.logger.Debug(ctx, "------ response ------\n"+string(resB)+"\n")
		}
	}

	defer res.Body.Close()

	if res.StatusCode >= 300 {
		body, _ := io.ReadAll(res.Body)
		return AdminClientError{
			StatusCode: res.StatusCode,
			Body:       body,
		}
	}

	if rcv == nil {
		if _, err := io.Copy(io.Discard, res.Body); err != nil {
			return fmt.Errorf("discarding response body: %w", err)
		}

		return nil
	}

	if err := json.NewDecoder(res.Body).Decode(rcv); err != nil {
		return fmt.Errorf("decoding json response body: %w", err)
	}

	return nil
}

// KnownNode describes the fields of a known node in the cluster, as returned
// as part of [ClusterStatus].
type KnownNode struct {
	ID              string         `json:"id"`
	Addr            netip.AddrPort `json:"addr"`
	IsUp            bool           `json:"isUp"`
	LastSeenSecsAgo int            `json:"lastSeenSecsAgo"`
	HostName        string         `json:"hostname"`
}

// Role descibes a node's role in the garage cluster, i.e. what storage it is
// providing.
type Role struct {
	ID       string   `json:"id"`
	Capacity int      `json:"capacity"` // Gb (SI units)
	Zone     string   `json:"zone"`
	Tags     []string `json:"tags"`
}

// ClusterLayout describes the layout of the cluster as a whole.
type ClusterLayout struct {
	Roles []Role `json:"roles"`
}

// ClusterStatus is returned from the Status endpoint, describing the currently
// known state of the cluster.
type ClusterStatus struct {
	Nodes  []KnownNode   `json:"nodes"`
	Layout ClusterLayout `json:"layout"`
}

// Status returns the current state of the cluster.
func (c *AdminClient) Status(ctx context.Context) (ClusterStatus, error) {
	// https://garagehq.deuxfleurs.fr/api/garage-admin-v1.html#tag/Nodes/operation/GetNodes
	var clusterStatus ClusterStatus
	err := c.do(ctx, &clusterStatus, "GET", "/v1/status", nil)
	return clusterStatus, err
}

// Wait will block until the instance connected to can see at least
// ReplicationFactor other garage instances. If the context is canceled it
// will return the context error.
func (c *AdminClient) Wait(ctx context.Context) error {

	for first := true; ; first = false {

		if !first {
			select {
			case <-time.After(500 * time.Millisecond):
			case <-ctx.Done():
				return ctx.Err()
			}
		}

		c.logger.Debug(ctx, "Getting cluster status")
		clusterStatus, err := c.Status(ctx)
		if ctxErr := ctx.Err(); ctxErr != nil {
			return ctxErr

		} else if err != nil {
			c.logger.Warn(ctx, "Instance is not yet ready", err)
			continue
		}

		var numUp int

		for _, node := range clusterStatus.Nodes {
			// There seems to be some kind of step between IsUp becoming true
			// and garage actually loading the full state of a node, so we check
			// for the HostName as well. We could also use LastSeenSecsAgo, but
			// that remains null for the node being queried so it's more
			// annoying to use.
			if node.IsUp && node.HostName != "" {
				numUp++
			}
		}

		ctx := mctx.Annotate(ctx,
			"numNodes", len(clusterStatus.Nodes),
			"numUp", numUp,
		)

		if numUp >= ReplicationFactor {
			c.logger.Debug(ctx, "instance appears to be online")
			return nil
		}

		c.logger.Debug(ctx, "Instance not online yet, will continue waiting")
	}
}

// CreateS3APICredentials creates an S3APICredentials with the given name. The
// credentials must be associated with a bucket via a call to
// GrantBucketPermissions in order to be useful.
func (c *AdminClient) CreateS3APICredentials(
	ctx context.Context, name string,
) (
	S3APICredentials, error,
) {
	// https://garagehq.deuxfleurs.fr/api/garage-admin-v1.html#tag/Key/operation/AddKey

	var res struct {
		ID     string `json:"accessKeyId"`
		Secret string `json:"secretAccessKey"`
	}

	// first attempt to import the key
	err := c.do(
		ctx, &res, "POST", "/v1/key", map[string]string{"name": name},
	)

	return S3APICredentials{
		ID:     res.ID,
		Secret: res.Secret,
	}, err
}

// CreateBucket creates a bucket with the given global alias, returning its ID.
func (c *AdminClient) CreateBucket(
	ctx context.Context, globalAlias string,
) (
	BucketID, error,
) {
	// https://garagehq.deuxfleurs.fr/api/garage-admin-v1.html#tag/Bucket/operation/PutBucketGlobalAlias

	var res struct {
		ID string `json:"id"`
	}

	err := c.do(
		ctx, &res, "POST", "/v1/bucket", map[string]string{
			"globalAlias": globalAlias,
		},
	)

	return BucketID(res.ID), err
}

// ListBuckets returns all buckets known to this garage node.
func (c *AdminClient) ListBuckets(ctx context.Context) ([]Bucket, error) {
	var res []Bucket
	err := c.do(ctx, &res, "GET", "/v1/bucket?list", nil)
	return res, err
}

// GrantBucketPermissions grants the S3APICredentials with the given ID
// permission(s) to interact with the bucket of the given ID.
func (c *AdminClient) GrantBucketPermissions(
	ctx context.Context,
	bucketID BucketID,
	credentialsID string,
	perms ...BucketPermission,
) error {
	permsMap := map[BucketPermission]bool{}
	for _, perm := range perms {
		permsMap[perm] = true
	}

	// https://garagehq.deuxfleurs.fr/api/garage-admin-v1.html#tag/Bucket/operation/AllowBucketKey
	return c.do(ctx, nil, "POST", "/v1/bucket/allow", map[string]any{
		"bucketId":    bucketID,
		"accessKeyId": credentialsID,
		"permissions": permsMap,
	})
}

// GetLayout returns the currently applied ClusterLayout.
func (c *AdminClient) GetLayout(ctx context.Context) (ClusterLayout, error) {
	// https://garagehq.deuxfleurs.fr/api/garage-admin-v1.html#tag/Layout/operation/GetLayout
	var res ClusterLayout
	err := c.do(ctx, &res, "GET", "/v1/layout", nil)
	return res, err
}

// ApplyLayout modifies the layout of the garage cluster. Only layout of the
// given roles will be modified/created/removed, other roles are not affected.
func (c *AdminClient) ApplyLayout(
	ctx context.Context, addModifyRoles []Role, removeRoleIDs []string,
) error {
	type removeRole struct {
		ID     string `json:"id"`
		Remove bool   `json:"remove"`
	}

	roles := make([]any, 0, len(addModifyRoles)+len(removeRoleIDs))
	for _, p := range addModifyRoles {
		roles = append(roles, p)
	}
	for _, id := range removeRoleIDs {
		roles = append(roles, removeRole{ID: id, Remove: true})
	}

	// https://garagehq.deuxfleurs.fr/api/garage-admin-v1.html#tag/Layout/operation/GetLayout
	var clusterLayout struct {
		Version           int    `json:"version"`
		StagedRoleChanges []Role `json:"stagedRoleChanges"`
	}

	// https://garagehq.deuxfleurs.fr/api/garage-admin-v1.html#tag/Layout/operation/ApplyLayout
	err := c.do(ctx, &clusterLayout, "POST", "/v1/layout", roles)
	if err != nil {
		return fmt.Errorf("staging layout changes: %w", err)
	} else if len(clusterLayout.StagedRoleChanges) == 0 {
		return nil
	}

	// https://garagehq.deuxfleurs.fr/api/garage-admin-v1.html#tag/Layout/operation/ApplyLayout
	applyClusterLayout := struct {
		Version int `json:"version"`
	}{
		Version: clusterLayout.Version + 1,
	}

	err = c.do(ctx, nil, "POST", "/v1/layout/apply", applyClusterLayout)
	if err != nil {
		return fmt.Errorf("applying new layout (new version:%d): %w", applyClusterLayout.Version, err)
	}

	return nil
}