package commands

import (
	"cmp"
	"context"
	"fmt"
	"io/fs"
	"os"
	"path/filepath"
	"regexp"
	"strings"

	tea "charm.land/bubbletea/v2"
	"github.com/charmbracelet/crush/internal/agent/tools/mcp"
	"github.com/charmbracelet/crush/internal/config"
	"github.com/charmbracelet/crush/internal/home"
	"github.com/charmbracelet/crush/internal/tui/components/chat"
	"github.com/charmbracelet/crush/internal/tui/util"
)

const (
	userCommandPrefix    = "user:"
	projectCommandPrefix = "project:"
)

var namedArgPattern = regexp.MustCompile(`\$([A-Z][A-Z0-9_]*)`)

type commandLoader struct {
	sources []commandSource
}

type commandSource struct {
	path   string
	prefix string
}

func LoadCustomCommands() ([]Command, error) {
	cfg := config.Get()
	if cfg == nil {
		return nil, fmt.Errorf("config not loaded")
	}

	loader := &commandLoader{
		sources: buildCommandSources(cfg),
	}

	return loader.loadAll()
}

func buildCommandSources(cfg *config.Config) []commandSource {
	var sources []commandSource

	// XDG config directory
	if dir := getXDGCommandsDir(); dir != "" {
		sources = append(sources, commandSource{
			path:   dir,
			prefix: userCommandPrefix,
		})
	}

	// Home directory
	if home := home.Dir(); home != "" {
		sources = append(sources, commandSource{
			path:   filepath.Join(home, ".crush", "commands"),
			prefix: userCommandPrefix,
		})
	}

	// Project directory
	sources = append(sources, commandSource{
		path:   filepath.Join(cfg.Options.DataDirectory, "commands"),
		prefix: projectCommandPrefix,
	})

	return sources
}

func getXDGCommandsDir() string {
	xdgHome := os.Getenv("XDG_CONFIG_HOME")
	if xdgHome == "" {
		if home := home.Dir(); home != "" {
			xdgHome = filepath.Join(home, ".config")
		}
	}
	if xdgHome != "" {
		return filepath.Join(xdgHome, "crush", "commands")
	}
	return ""
}

func (l *commandLoader) loadAll() ([]Command, error) {
	var commands []Command

	for _, source := range l.sources {
		if cmds, err := l.loadFromSource(source); err == nil {
			commands = append(commands, cmds...)
		}
	}

	return commands, nil
}

func (l *commandLoader) loadFromSource(source commandSource) ([]Command, error) {
	if err := ensureDir(source.path); err != nil {
		return nil, err
	}

	var commands []Command

	err := filepath.WalkDir(source.path, func(path string, d fs.DirEntry, err error) error {
		if err != nil || d.IsDir() || !isMarkdownFile(d.Name()) {
			return err
		}

		cmd, err := l.loadCommand(path, source.path, source.prefix)
		if err != nil {
			return nil // Skip invalid files
		}

		commands = append(commands, cmd)
		return nil
	})

	return commands, err
}

func (l *commandLoader) loadCommand(path, baseDir, prefix string) (Command, error) {
	content, err := os.ReadFile(path)
	if err != nil {
		return Command{}, err
	}

	id := buildCommandID(path, baseDir, prefix)
	desc := fmt.Sprintf("Custom command from %s", filepath.Base(path))

	return Command{
		ID:          id,
		Title:       id,
		Description: desc,
		Handler:     createCommandHandler(id, desc, string(content)),
	}, nil
}

func buildCommandID(path, baseDir, prefix string) string {
	relPath, _ := filepath.Rel(baseDir, path)
	parts := strings.Split(relPath, string(filepath.Separator))

	// Remove .md extension from last part
	if len(parts) > 0 {
		lastIdx := len(parts) - 1
		parts[lastIdx] = strings.TrimSuffix(parts[lastIdx], filepath.Ext(parts[lastIdx]))
	}

	return prefix + strings.Join(parts, ":")
}

func createCommandHandler(id, desc, content string) func(Command) tea.Cmd {
	return func(cmd Command) tea.Cmd {
		args := extractArgNames(content)

		if len(args) == 0 {
			return util.CmdHandler(CommandRunCustomMsg{
				Content: content,
			})
		}
		return util.CmdHandler(ShowArgumentsDialogMsg{
			CommandID:   id,
			Description: desc,
			ArgNames:    args,
			OnSubmit: func(args map[string]string) tea.Cmd {
				return execUserPrompt(content, args)
			},
		})
	}
}

func execUserPrompt(content string, args map[string]string) tea.Cmd {
	return func() tea.Msg {
		for name, value := range args {
			placeholder := "$" + name
			content = strings.ReplaceAll(content, placeholder, value)
		}
		return CommandRunCustomMsg{
			Content: content,
		}
	}
}

func extractArgNames(content string) []string {
	matches := namedArgPattern.FindAllStringSubmatch(content, -1)
	if len(matches) == 0 {
		return nil
	}

	seen := make(map[string]bool)
	var args []string

	for _, match := range matches {
		arg := match[1]
		if !seen[arg] {
			seen[arg] = true
			args = append(args, arg)
		}
	}

	return args
}

func ensureDir(path string) error {
	if _, err := os.Stat(path); os.IsNotExist(err) {
		return os.MkdirAll(path, 0o755)
	}
	return nil
}

func isMarkdownFile(name string) bool {
	return strings.HasSuffix(strings.ToLower(name), ".md")
}

type CommandRunCustomMsg struct {
	Content string
}

func loadMCPPrompts() []Command {
	var commands []Command
	for mcpName, prompts := range mcp.Prompts() {
		for _, prompt := range prompts {
			key := mcpName + ":" + prompt.Name
			commands = append(commands, Command{
				ID:          key,
				Title:       cmp.Or(prompt.Title, prompt.Name),
				Description: prompt.Description,
				Handler:     createMCPPromptHandler(mcpName, prompt.Name, prompt),
			})
		}
	}

	return commands
}

func createMCPPromptHandler(mcpName, promptName string, prompt *mcp.Prompt) func(Command) tea.Cmd {
	return func(cmd Command) tea.Cmd {
		if len(prompt.Arguments) == 0 {
			return execMCPPrompt(mcpName, promptName, nil)
		}
		return util.CmdHandler(ShowMCPPromptArgumentsDialogMsg{
			Prompt: prompt,
			OnSubmit: func(args map[string]string) tea.Cmd {
				return execMCPPrompt(mcpName, promptName, args)
			},
		})
	}
}

func execMCPPrompt(clientName, promptName string, args map[string]string) tea.Cmd {
	return func() tea.Msg {
		ctx := context.Background()
		result, err := mcp.GetPromptMessages(ctx, clientName, promptName, args)
		if err != nil {
			return util.ReportError(err)
		}

		return chat.SendMsg{
			Text: strings.Join(result, " "),
		}
	}
}

type ShowMCPPromptArgumentsDialogMsg struct {
	Prompt   *mcp.Prompt
	OnSubmit func(arg map[string]string) tea.Cmd
}