package bootstrap

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

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

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

type Handler func(context.Context, Invocation) error

type Hooks struct {
	Setup   Handler
	MCP     Handler
	Config  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)
	}

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

	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]), nil, true
		}
		return "", nil, true
	}

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

	return command, commandArgs, 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) error {
	if command == "" {
		return printGlobalHelp(opts)
	}

	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 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
}