package internal

import (
	"os"
	"path/filepath"
	"sort"
	"strings"
	"unicode/utf8"

	tea "charm.land/bubbletea/v2"
)

// ScanSkillsCompleteMsg 技能扫描完成消息
type ScanSkillsCompleteMsg struct {
	Skills []*SkillInfo
}

// ScanSkillsCmd 扫描 ~/.claude/skills/ 目录
func ScanSkillsCmd() tea.Cmd {
	return func() tea.Msg {
		skills, err := ScanSkills()
		if err != nil {
			return ScanSkillsCompleteMsg{}
		}
		return ScanSkillsCompleteMsg{Skills: skills}
	}
}

// SkillInfo 单个技能信息
type SkillInfo struct {
	Name        string
	Dir         string
	Description string
	Root        *SkillFileNode
}

// SkillFileNode 技能文件树节点
type SkillFileNode struct {
	Name     string
	Path     string
	IsDir    bool
	Expanded bool
	Children []*SkillFileNode
}

// SkillsState 技能 tab 视图状态
type SkillsState struct {
	Skills        []*SkillInfo
	SkillCur      int // 技能列表光标 (panel 0)
	FileCur       int // 文件树光标 (panel 1)
	FocusPanel    int // 0=技能列表 1=文件树 2=内容
	Content       string
	ContentPath   string
	ContentScroll int // 内容面板纵向滚动偏移（行）
	Loaded        bool
	Scanning      bool
}

// flatNode 文件树扁平化节点
type flatNode struct {
	*SkillFileNode
	Depth int
}

// ScanSkills 扫描 ~/.claude/skills/ 目录
func ScanSkills() ([]*SkillInfo, error) {
	home, err := os.UserHomeDir()
	if err != nil {
		return nil, err
	}
	skillsDir := filepath.Join(home, ".claude", "skills")
	return scanSkillsDir(skillsDir)
}

func scanSkillsDir(dir string) ([]*SkillInfo, error) {
	entries, err := os.ReadDir(dir)
	if err != nil {
		return nil, err
	}
	var skills []*SkillInfo
	for _, entry := range entries {
		if !entry.IsDir() {
			continue
		}
		name := entry.Name()
		if strings.HasPrefix(name, ".") {
			continue
		}
		skillPath := filepath.Join(dir, name)
		info := &SkillInfo{
			Name: name,
			Dir:  skillPath,
		}
		// 读取 SKILL.md 获取描述
		skillMd := filepath.Join(skillPath, "SKILL.md")
		if data, err := os.ReadFile(skillMd); err == nil {
			info.Description = extractSkillDesc(string(data))
		}
		// 构建文件树
		info.Root = buildFileTree(skillPath)
		if info.Root != nil {
			info.Root.Expanded = true // 默认展开根节点
		}
		skills = append(skills, info)
	}
	sort.Slice(skills, func(i, j int) bool {
		return skills[i].Name < skills[j].Name
	})
	return skills, nil
}

// extractSkillDesc 从 SKILL.md 提取描述文本
func extractSkillDesc(content string) string {
	lines := strings.Split(content, "\n")
	afterHeading := false
	for _, line := range lines {
		line = strings.TrimSpace(line)
		if strings.HasPrefix(line, "#") {
			afterHeading = true
			continue
		}
		// 跳过分隔线、引言、元数据
		if strings.HasPrefix(line, "---") || strings.HasPrefix(line, ">") ||
			strings.HasPrefix(line, "##") || strings.HasPrefix(line, "|") ||
			strings.HasPrefix(line, "```") || strings.HasPrefix(line, "<!--") {
			continue
		}
		if afterHeading && line != "" {
			return truncStr(line, 80)
		}
	}
	return ""
}

// buildFileTree 递归构建文件树
func buildFileTree(rootPath string) *SkillFileNode {
	info, err := os.Stat(rootPath)
	if err != nil {
		return nil
	}
	node := &SkillFileNode{
		Name:  filepath.Base(rootPath),
		Path:  rootPath,
		IsDir: info.IsDir(),
	}
	if !info.IsDir() {
		return node
	}
	entries, err := os.ReadDir(rootPath)
	if err != nil {
		return node
	}
	for _, entry := range entries {
		name := entry.Name()
		if strings.HasPrefix(name, ".") {
			continue
		}
		child := buildFileTree(filepath.Join(rootPath, name))
		if child != nil {
			node.Children = append(node.Children, child)
		}
	}
	// 排序：目录在前，文件在后；同类型按字母序
	sort.Slice(node.Children, func(i, j int) bool {
		if node.Children[i].IsDir != node.Children[j].IsDir {
			return node.Children[i].IsDir
		}
		return node.Children[i].Name < node.Children[j].Name
	})
	return node
}

// --- 文件树扁平化 ---

func (m *Model) skillsFlattened() []flatNode {
	s := m.currentSkill()
	if s == nil || s.Root == nil {
		return nil
	}
	return flattenNode(s.Root, 0)
}

func flattenNode(node *SkillFileNode, depth int) []flatNode {
	var result []flatNode
	result = append(result, flatNode{SkillFileNode: node, Depth: depth})
	if node.IsDir && node.Expanded {
		for _, child := range node.Children {
			result = append(result, flattenNode(child, depth+1)...)
		}
	}
	return result
}

// --- 查找与导航 ---

func (m *Model) currentSkill() *SkillInfo {
	if m.Skills.Skills == nil || m.Skills.SkillCur < 0 || m.Skills.SkillCur >= len(m.Skills.Skills) {
		return nil
	}
	return m.Skills.Skills[m.Skills.SkillCur]
}

func (m *Model) currentFlatNode() *flatNode {
	flat := m.skillsFlattened()
	if flat == nil || m.Skills.FileCur < 0 || m.Skills.FileCur >= len(flat) {
		return nil
	}
	return &flat[m.Skills.FileCur]
}

// loadSkillContent 加载文件内容到右侧面板
func (m *Model) loadSkillContent(path string) {
	data, err := os.ReadFile(path)
	if err != nil {
		m.Skills.Content = "无法读取文件"
		m.Skills.ContentPath = path
		return
	}
	m.Skills.Content = truncateSkillContent(string(data), 100*1024)
	m.Skills.ContentPath = path
	m.Skills.ContentScroll = 0
}

// truncateSkillContent 限制内容大小避免大文件卡顿；截断点可能落在
// UTF-8 多字节序列中间，逐字节回退到合法边界，避免尾部出现乱码
func truncateSkillContent(content string, limit int) string {
	if len(content) <= limit {
		return content
	}
	content = content[:limit]
	for len(content) > 0 {
		if r, size := utf8.DecodeLastRuneInString(content); r != utf8.RuneError || size > 1 {
			break
		}
		content = content[:len(content)-1]
	}
	return content + "\n\n... (文件过大，截断显示)"
}

// IsSkillsTab 判断当前是否在技能 tab
func (m *Model) IsSkillsTab() bool {
	return m.activeGroup == len(Groups)+1
}

// --- 文件树节点操作 ---

// findNodeByPath 在树中按路径查找节点
func findNodeByPath(root *SkillFileNode, path string) *SkillFileNode {
	if root == nil {
		return nil
	}
	if root.Path == path {
		return root
	}
	for _, child := range root.Children {
		if found := findNodeByPath(child, path); found != nil {
			return found
		}
	}
	return nil
}