package bootstrap

import (
	"context"
	"errors"
	"fmt"
	"io"
	"os"
	"strings"
)

const (
	CommandSetup   = "setup"
	CommandMCP     = "mcp"
	CommandConfig  = "config"
	CommandUpdate  = "update"
	CommandVersion = "version"

	ConfigSubcommandShow   = "show"
	ConfigSubcommandTest   = "test"
	ConfigSubcommandDelete = "delete"
)

var (
	ErrBinaryNameRequired   = errors.New("binary name is required")
	ErrUnknownCommand       = errors.New("unknown command")
	ErrUnknownSubcommand    = errors.New("unknown subcommand")
	ErrCommandNotConfigured = errors.New("command not configured")
	ErrVersionRequired      = errors.New("version is required when no version hook is configured")
	ErrSubcommandRequired   = errors.New("subcommand is required")
)

type Handler func(context.Context, Invocation) error

type Hooks struct {
	Setup        Handler
	MCP          Handler
	Config       Handler
	ConfigShow   Handler
	ConfigTest   Handler
	ConfigDelete Handler
	Update       Handler
	Version      Handler
}

type Options struct {
	BinaryName  string
	Description string
	Version     string
	Args        []string
	Stdin       io.Reader
	Stdout      io.Writer
	Stderr      io.Writer
	Hooks       Hooks
}

type Invocation struct {
	Command string
	Args    []string
	Stdin   io.Reader
	Stdout  io.Writer
	Stderr  io.Writer
}

type commandDef struct {
	Name        string
	Description string
	Handler     func(Hooks) Handler
}

var commands = []commandDef{
	{
		Name:        CommandSetup,
		Description: "Initialiser ou mettre a jour la configuration locale.",
		Handler: func(h Hooks) Handler {
			return h.Setup
		},
	},
	{
		Name:        CommandMCP,
		Description: "Executer la logique MCP principale du binaire.",
		Handler: func(h Hooks) Handler {
			return h.MCP
		},
	},
	{
		Name:        CommandConfig,
		Description: "Inspecter ou modifier la configuration.",
		Handler: func(h Hooks) Handler {
			return h.Config
		},
	},
	{
		Name:        CommandUpdate,
		Description: "Declencher le flux d'auto-update.",
		Handler: func(h Hooks) Handler {
			return h.Update
		},
	},
	{
		Name:        CommandVersion,
		Description: "Afficher la version du binaire.",
		Handler: func(h Hooks) Handler {
			return h.Version
		},
	},
}

func Run(ctx context.Context, opts Options) error {
	normalized := normalize(opts)

	if strings.TrimSpace(normalized.BinaryName) == "" {
		return ErrBinaryNameRequired
	}

	command, commandArgs, showHelp := parseArgs(normalized.Args)
	if showHelp {
		return printHelp(normalized, command, commandArgs)
	}

	if command == "" {
		return printHelp(normalized, "")
	}

	if command == CommandConfig {
		return runConfigCommand(ctx, normalized, commandArgs)
	}

	handler, known := resolveHandler(command, normalized.Hooks)
	if !known {
		return fmt.Errorf("%w: %s", ErrUnknownCommand, command)
	}

	if handler == nil {
		if command == CommandVersion {
			if strings.TrimSpace(normalized.Version) == "" {
				return ErrVersionRequired
			}
			_, err := fmt.Fprintln(normalized.Stdout, normalized.Version)
			return err
		}
		return fmt.Errorf("%w: %s", ErrCommandNotConfigured, command)
	}

	return handler(ctx, Invocation{
		Command: command,
		Args:    commandArgs,
		Stdin:   normalized.Stdin,
		Stdout:  normalized.Stdout,
		Stderr:  normalized.Stderr,
	})
}

func normalize(opts Options) Options {
	if opts.Stdin == nil {
		opts.Stdin = os.Stdin
	}
	if opts.Stdout == nil {
		opts.Stdout = os.Stdout
	}
	if opts.Stderr == nil {
		opts.Stderr = os.Stderr
	}
	if opts.Args == nil {
		opts.Args = os.Args[1:]
	}
	return opts
}

func parseArgs(args []string) (command string, commandArgs []string, showHelp bool) {
	if len(args) == 0 {
		return "", nil, false
	}

	first := strings.TrimSpace(args[0])
	switch first {
	case "help", "-h", "--help":
		if len(args) > 1 {
			return strings.TrimSpace(args[1]), trimArgs(args[2:]), true
		}
		return "", nil, true
	}

	command = first
	commandArgs = trimArgs(args[1:])
	if len(commandArgs) > 0 {
		last := strings.TrimSpace(commandArgs[len(commandArgs)-1])
		if last == "-h" || last == "--help" {
			return command, commandArgs[:len(commandArgs)-1], true
		}
	}

	return command, commandArgs, false
}

func trimArgs(args []string) []string {
	if len(args) == 0 {
		return nil
	}

	result := make([]string, 0, len(args))
	for _, arg := range args {
		trimmed := strings.TrimSpace(arg)
		if trimmed == "" {
			continue
		}
		result = append(result, trimmed)
	}
	return result
}

func runConfigCommand(ctx context.Context, opts Options, args []string) error {
	if len(args) == 0 {
		return fmt.Errorf("%w: %s requires one of: %s, %s", ErrSubcommandRequired, CommandConfig, ConfigSubcommandShow, ConfigSubcommandTest)
	}

	subcommand := strings.TrimSpace(args[0])
	subcommandArgs := args[1:]

	handler, known := resolveConfigHandler(opts.Hooks, subcommand)
	if !known {
		if opts.Hooks.Config != nil {
			return opts.Hooks.Config(ctx, Invocation{
				Command: CommandConfig,
				Args:    args,
				Stdin:   opts.Stdin,
				Stdout:  opts.Stdout,
				Stderr:  opts.Stderr,
			})
		}
		return fmt.Errorf("%w: %s %s", ErrUnknownSubcommand, CommandConfig, subcommand)
	}

	if handler == nil {
		if opts.Hooks.Config != nil {
			return opts.Hooks.Config(ctx, Invocation{
				Command: fmt.Sprintf("%s %s", CommandConfig, subcommand),
				Args:    subcommandArgs,
				Stdin:   opts.Stdin,
				Stdout:  opts.Stdout,
				Stderr:  opts.Stderr,
			})
		}
		return fmt.Errorf("%w: %s %s", ErrCommandNotConfigured, CommandConfig, subcommand)
	}

	return handler(ctx, Invocation{
		Command: fmt.Sprintf("%s %s", CommandConfig, subcommand),
		Args:    subcommandArgs,
		Stdin:   opts.Stdin,
		Stdout:  opts.Stdout,
		Stderr:  opts.Stderr,
	})
}

func resolveConfigHandler(hooks Hooks, subcommand string) (Handler, bool) {
	switch subcommand {
	case ConfigSubcommandShow:
		return hooks.ConfigShow, true
	case ConfigSubcommandTest:
		return hooks.ConfigTest, true
	case ConfigSubcommandDelete:
		return hooks.ConfigDelete, true
	default:
		return nil, false
	}
}

func resolveHandler(command string, hooks Hooks) (Handler, bool) {
	for _, def := range commands {
		if def.Name == command {
			return def.Handler(hooks), true
		}
	}
	return nil, false
}

func printHelp(opts Options, command string, args ...[]string) error {
	var commandArgs []string
	if len(args) > 0 {
		commandArgs = args[0]
	}

	if command == "" {
		return printGlobalHelp(opts)
	}

	if command == CommandConfig {
		return printConfigHelp(opts, commandArgs)
	}

	for _, def := range commands {
		if def.Name != command {
			continue
		}
		_, err := fmt.Fprintf(
			opts.Stdout,
			"Usage:\n  %s %s [args]\n\n%s\n",
			opts.BinaryName,
			def.Name,
			def.Description,
		)
		return err
	}

	return fmt.Errorf("%w: %s", ErrUnknownCommand, command)
}

func printConfigHelp(opts Options, args []string) error {
	if len(args) == 0 {
		_, err := fmt.Fprintf(
			opts.Stdout,
			"Usage:\n  %s config <subcommand> [args]\n\nSubcommandes:\n  %-7s Afficher la configuration résolue et la provenance des valeurs.\n  %-7s Vérifier la configuration et la connectivité.\n  %-7s Supprimer un profil local (optionnel).\n",
			opts.BinaryName,
			ConfigSubcommandShow,
			ConfigSubcommandTest,
			ConfigSubcommandDelete,
		)
		return err
	}

	switch args[0] {
	case ConfigSubcommandShow:
		_, err := fmt.Fprintf(
			opts.Stdout,
			"Usage:\n  %s config %s [args]\n\nAfficher la configuration résolue et l'origine des valeurs.\n",
			opts.BinaryName,
			ConfigSubcommandShow,
		)
		return err
	case ConfigSubcommandTest:
		_, err := fmt.Fprintf(
			opts.Stdout,
			"Usage:\n  %s config %s [args]\n\nTester la configuration résolue et la connectivité associée.\n",
			opts.BinaryName,
			ConfigSubcommandTest,
		)
		return err
	case ConfigSubcommandDelete:
		_, err := fmt.Fprintf(
			opts.Stdout,
			"Usage:\n  %s config %s [args]\n\nSupprimer un profil local de configuration.\n",
			opts.BinaryName,
			ConfigSubcommandDelete,
		)
		return err
	default:
		return fmt.Errorf("%w: %s %s", ErrUnknownSubcommand, CommandConfig, args[0])
	}
}

func printGlobalHelp(opts Options) error {
	if strings.TrimSpace(opts.Description) != "" {
		if _, err := fmt.Fprintf(opts.Stdout, "%s\n\n", opts.Description); err != nil {
			return err
		}
	}

	if _, err := fmt.Fprintf(opts.Stdout, "Usage:\n  %s <command> [args]\n\n", opts.BinaryName); err != nil {
		return err
	}
	if _, err := fmt.Fprintln(opts.Stdout, "Commandes communes:"); err != nil {
		return err
	}

	for _, def := range commands {
		if _, err := fmt.Fprintf(opts.Stdout, "  %-7s %s\n", def.Name, def.Description); err != nil {
			return err
		}
	}

	_, err := fmt.Fprintf(opts.Stdout, "\nAide detaillee: %s help <command>\n", opts.BinaryName)
	return err
}