package main

import (
	"context"
	"errors"
	"fmt"
	"io"
	"isle/daemon"
	"isle/jsonutil"
	"os"
	"strings"

	"dev.mediocregopher.com/mediocre-go-lib.git/mlog"
	"github.com/spf13/pflag"
	"gopkg.in/yaml.v3"
)

type subCmd struct {
	name  string
	descr string
	do    func(subCmdCtx) error

	// If set then the name will be allowed to be suffixed with this string.
	plural string
}

func (c subCmd) fullName() string {
	name := c.name
	if c.plural != "" {
		name += "(" + c.plural + ")"
	}
	return name
}

type subCmdCtxOpts struct {
	args         []string // command-line arguments, excluding the subCmd itself.
	subCmdNames  []string // names of subCmds so far, including this one
	stdout       io.Writer
	changeStager *changeStager
}

func (o *subCmdCtxOpts) withDefaults() *subCmdCtxOpts {
	if o == nil {
		o = new(subCmdCtxOpts)
	}

	if o.args == nil {
		o.args = os.Args[1:]
	}

	if o.stdout == nil {
		o.stdout = os.Stdout
	}

	return o
}

// subCmdCtx contains all information available to a subCmd's do method.
type subCmdCtx struct {
	context.Context
	logger    *mlog.Logger
	daemonRPC daemon.RPC
	subCmd    subCmd // the subCmd itself
	opts      *subCmdCtxOpts

	flags *pflag.FlagSet
}

func newSubCmdCtx(
	ctx context.Context,
	logger *mlog.Logger,
	daemonRPC daemon.RPC,
	subCmd subCmd,
	opts *subCmdCtxOpts,
) subCmdCtx {
	opts = opts.withDefaults()

	return subCmdCtx{
		Context:   ctx,
		logger:    logger,
		daemonRPC: daemonRPC,
		subCmd:    subCmd,
		opts:      opts,
		flags:     pflag.NewFlagSet(subCmd.name, pflag.ExitOnError),
	}
}

func (ctx subCmdCtx) getChangeStager() *changeStager {
	if ctx.opts.changeStager != nil {
		return ctx.opts.changeStager
	}

	return &changeStager{envCacheDir()}
}

func usagePrefix(subCmdNames []string) string {
	subCmdNamesStr := strings.Join(subCmdNames, " ")
	if subCmdNamesStr != "" {
		subCmdNamesStr += " "
	}

	return fmt.Sprintf("USAGE:\n  %s %s", os.Args[0], subCmdNamesStr)
}

type withParsedFlagsOpts struct {
	// noNetwork, if true, means the call doesn't require a network to be
	// specified on the command-line if there are more than one networks
	// configured.
	noNetwork bool

	// Extra arguments on the command-line will be passed through to some
	// underlying command.
	passthroughArgs bool
}

func (o *withParsedFlagsOpts) withDefaults() *withParsedFlagsOpts {
	if o == nil {
		o = new(withParsedFlagsOpts)
	}
	return o
}

func (ctx subCmdCtx) withParsedFlags(
	opts *withParsedFlagsOpts,
) (
	subCmdCtx, error,
) {
	opts = opts.withDefaults()

	logLevel := logLevelFlag{mlog.LevelInfo}
	ctx.flags.VarP(
		&logLevel,
		"log-level", "l",
		"Maximum log level to output. Can be DEBUG, CHILD, INFO, WARN, ERROR, or FATAL.",
	)

	var network string
	if !opts.noNetwork {
		ctx.flags.StringVar(
			&network,
			"network", "",
			"Which network to perform the command against, if more than one is joined. Can be an ID, name, or domain.",
		)
	}

	ctx.flags.VisitAll(func(f *pflag.Flag) {
		if f.Shorthand == "h" {
			panic(fmt.Sprintf("flag %+v has reserved shorthand `-h`", f))
		}
		if f.Name == "help" {
			panic(fmt.Sprintf("flag %+v has reserved name `--help`", f))
		}
	})

	ctx.flags.Usage = func() {
		if ctx.subCmd.descr != "" {
			fmt.Fprintf(
				os.Stderr, "\nDESCRIPTION:\n  %s\n\n", ctx.subCmd.descr,
			)
		}

		var passthroughStr string
		if opts.passthroughArgs {
			passthroughStr = " [--] [args...]"
		}

		fmt.Fprintf(
			os.Stderr, "%s[-h|--help] [%s flags...]%s\n\n",
			usagePrefix(ctx.opts.subCmdNames), ctx.subCmd.name, passthroughStr,
		)

		fmt.Fprintf(
			os.Stderr, "%s FLAGS:\n", strings.ToUpper(ctx.subCmd.name),
		)
		fmt.Fprintln(os.Stderr, ctx.flags.FlagUsages())

		os.Stderr.Sync()
		os.Exit(2)
	}

	if err := ctx.flags.Parse(ctx.opts.args); err != nil {
		return ctx, err
	}

	ctx.Context = daemon.WithNetwork(ctx.Context, network)
	ctx.logger = ctx.logger.WithMaxLevel(logLevel.Int())

	return ctx, nil
}

func (ctx subCmdCtx) doSubCmd(subCmds ...subCmd) error {

	printUsageExit := func(subCmdName string) {

		fmt.Fprintf(os.Stderr, "unknown sub-command %q\n\n", subCmdName)

		if ctx.subCmd.descr != "" {
			fmt.Fprintf(
				os.Stderr, "DESCRIPTION:\n  %s\n\n", ctx.subCmd.descr,
			)
		}

		fmt.Fprintf(
			os.Stderr,
			"%s<subCmd> [-h|--help] [sub-command flags...]\n\n",
			usagePrefix(ctx.opts.subCmdNames),
		)

		fmt.Fprintf(os.Stderr, "SUB-COMMANDS:\n")

		var maxNameLen int
		for _, subCmd := range subCmds {
			l := len(subCmd.fullName())
			if l > maxNameLen {
				maxNameLen = l
			}
		}

		for _, subCmd := range subCmds {
			var (
				name    = subCmd.fullName()
				padding = strings.Repeat(" ", maxNameLen-len(name)+3)
			)

			fmt.Fprintf(
				os.Stderr, "  %s%s%s\n", name, padding, subCmd.descr,
			)
		}

		fmt.Fprintf(os.Stderr, "\n")
		os.Stderr.Sync()
		os.Exit(2)
	}

	args := ctx.opts.args

	if len(args) == 0 {
		printUsageExit("")
	}

	subCmdsMap := map[string]subCmd{}
	for _, subCmd := range subCmds {
		subCmdsMap[subCmd.name] = subCmd
		if subCmd.plural != "" {
			subCmdsMap[subCmd.name+subCmd.plural] = subCmd
		}
	}

	subCmdName, args := args[0], args[1:]

	subCmd, ok := subCmdsMap[subCmdName]
	if !ok {
		printUsageExit(subCmdName)
	}

	nextSubCmdCtxOpts := *ctx.opts
	nextSubCmdCtxOpts.args = args
	nextSubCmdCtxOpts.subCmdNames = append(ctx.opts.subCmdNames, subCmdName)

	nextSubCmdCtx := newSubCmdCtx(
		ctx.Context, ctx.logger, ctx.daemonRPC, subCmd, &nextSubCmdCtxOpts,
	)

	if err := subCmd.do(nextSubCmdCtx); err != nil {
		return err
	}

	return nil
}

type outputFormat string

func (f outputFormat) MarshalText() ([]byte, error) { return []byte(f), nil }

func (f *outputFormat) UnmarshalText(b []byte) error {
	*f = outputFormat(strings.ToLower(string(b)))
	switch *f {
	case "json", "yaml":
		return nil
	default:
		return errors.New("invalid output format")
	}
}

// doWithOutput wraps a subCmd's do function so that it will output some value
// to stdout. The value will be formatted according to a command-line argument.
func doWithOutput(fn func(subCmdCtx) (any, error)) func(subCmdCtx) error {
	return func(ctx subCmdCtx) error {
		type outputFormatFlag = textUnmarshalerFlag[outputFormat, *outputFormat]

		outputFormat := outputFormatFlag{"yaml"}
		ctx.flags.Var(
			&outputFormat,
			"format",
			"How to format the output value. Can be 'json' or 'yaml'.",
		)

		res, err := fn(ctx)
		if err != nil {
			return err
		}

		switch outputFormat.V {
		case "json":
			return jsonutil.WriteIndented(ctx.opts.stdout, res)
		case "yaml":
			return yaml.NewEncoder(ctx.opts.stdout).Encode(res)
		default:
			panic(fmt.Sprintf("unexpected outputFormat %q", outputFormat))
		}
	}
}