package skills

import (
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"time"

	"gopkg.in/yaml.v3"
)

type Skill struct {
	Name        string    `yaml:"name" json:"name"`
	Description string    `yaml:"description" json:"description"`
	Content     string    `yaml:"content" json:"content"`
	Author      string    `yaml:"author" json:"author"`
	Version     string    `yaml:"version" json:"version"`
	CreatedAt   time.Time `yaml:"created_at" json:"created_at"`
	UpdatedAt   time.Time `yaml:"updated_at" json:"updated_at"`
	Tags        []string  `yaml:"tags" json:"tags"`
	Target      string    `yaml:"target" json:"target"`
	FilePath    string    `yaml:"-" json:"-"`
}

func SkillsDir() (string, error) {
	home, err := os.UserHomeDir()
	if err != nil {
		return "", err
	}
	dir := filepath.Join(home, ".muyue", "skills")
	return dir, nil
}

func List() ([]Skill, error) {
	dir, err := SkillsDir()
	if err != nil {
		return nil, err
	}

	entries, err := os.ReadDir(dir)
	if err != nil {
		if os.IsNotExist(err) {
			return []Skill{}, nil
		}
		return nil, err
	}

	var skills []Skill
	for _, e := range entries {
		if !e.IsDir() {
			continue
		}
		skillPath := filepath.Join(dir, e.Name(), "SKILL.md")
		data, err := os.ReadFile(skillPath)
		if err != nil {
			continue
		}
		skill, err := parseSkill(data)
		if err != nil {
			continue
		}
		skill.FilePath = skillPath
		skill.Name = e.Name()
		skills = append(skills, *skill)
	}

	sort.Slice(skills, func(i, j int) bool {
		return skills[i].Name < skills[j].Name
	})

	return skills, nil
}

func Get(name string) (*Skill, error) {
	dir, err := SkillsDir()
	if err != nil {
		return nil, err
	}

	skillPath := filepath.Join(dir, name, "SKILL.md")
	data, err := os.ReadFile(skillPath)
	if err != nil {
		return nil, fmt.Errorf("skill '%s' not found", name)
	}

	skill, err := parseSkill(data)
	if err != nil {
		return nil, err
	}
	skill.FilePath = skillPath
	skill.Name = name
	return skill, nil
}

func Create(skill *Skill) error {
	dir, err := SkillsDir()
	if err != nil {
		return err
	}

	skillDir := filepath.Join(dir, skill.Name)
	if err := os.MkdirAll(skillDir, 0755); err != nil {
		return err
	}

	skillPath := filepath.Join(skillDir, "SKILL.md")
	content := renderSkill(skill)
	if err := os.WriteFile(skillPath, []byte(content), 0644); err != nil {
		return err
	}

	return Deploy(skill)
}

func Delete(name string) error {
	dir, err := SkillsDir()
	if err != nil {
		return err
	}

	skillDir := filepath.Join(dir, name)
	if err := os.RemoveAll(skillDir); err != nil {
		return err
	}

	undeployFromTargets(name)
	return nil
}

func Deploy(skill *Skill) error {
	home, err := os.UserHomeDir()
	if err != nil {
		return fmt.Errorf("get home dir: %w", err)
	}

	if skill.Target == "crush" || skill.Target == "both" {
		crushSkillsDir := filepath.Join(home, ".config", "crush", "skills")
		if err := os.MkdirAll(crushSkillsDir, 0755); err != nil {
			return fmt.Errorf("create crush skills dir: %w", err)
		}
		target := filepath.Join(crushSkillsDir, skill.Name)
		if err := os.MkdirAll(target, 0755); err != nil {
			return fmt.Errorf("create skill dir: %w", err)
		}
		content := renderSkill(skill)
		if err := os.WriteFile(filepath.Join(target, "SKILL.md"), []byte(content), 0644); err != nil {
			return fmt.Errorf("write crush skill: %w", err)
		}
	}

	if skill.Target == "claude" || skill.Target == "both" {
		claudeSkillsDir := filepath.Join(home, ".claude", "skills")
		if err := os.MkdirAll(claudeSkillsDir, 0755); err != nil {
			return fmt.Errorf("create claude skills dir: %w", err)
		}
		target := filepath.Join(claudeSkillsDir, skill.Name)
		if err := os.MkdirAll(target, 0755); err != nil {
			return fmt.Errorf("create skill dir: %w", err)
		}
		content := renderSkill(skill)
		if err := os.WriteFile(filepath.Join(target, "SKILL.md"), []byte(content), 0644); err != nil {
			return fmt.Errorf("write claude skill: %w", err)
		}
	}

	return nil
}

func DeployAll() error {
	skills, err := List()
	if err != nil {
		return err
	}
	for _, s := range skills {
		if err := Deploy(&s); err != nil {
			return fmt.Errorf("deploy %s: %w", s.Name, err)
		}
	}
	return nil
}

func undeployFromTargets(name string) {
	home, _ := os.UserHomeDir()

	os.RemoveAll(filepath.Join(home, ".config", "crush", "skills", name))
	os.RemoveAll(filepath.Join(home, ".claude", "skills", name))
}

func parseSkill(data []byte) (*Skill, error) {
	content := string(data)

	if !strings.HasPrefix(content, "---") {
		return &Skill{Content: content}, nil
	}

	end := strings.Index(content[3:], "---")
	if end == -1 {
		return &Skill{Content: content}, nil
	}

	frontmatter := content[3 : end+3]
	body := strings.TrimSpace(content[end+6:])

	skill := &Skill{Content: body}

	if err := yaml.Unmarshal([]byte(frontmatter), skill); err != nil {
		return &Skill{Content: content}, nil
	}

	return skill, nil
}

func renderSkill(skill *Skill) string {
	var b strings.Builder

	b.WriteString("---\n")
	b.WriteString(fmt.Sprintf("name: %s\n", skill.Name))
	b.WriteString(fmt.Sprintf("description: %s\n", skill.Description))
	if skill.Author != "" {
		b.WriteString(fmt.Sprintf("author: %s\n", skill.Author))
	}
	if skill.Version != "" {
		b.WriteString(fmt.Sprintf("version: %s\n", skill.Version))
	}
	if skill.Target != "" {
		b.WriteString(fmt.Sprintf("target: %s\n", skill.Target))
	}
	if len(skill.Tags) > 0 {
		b.WriteString(fmt.Sprintf("tags: [%s]\n", strings.Join(skill.Tags, ", ")))
	}
	b.WriteString("---\n\n")
	b.WriteString(skill.Content)
	b.WriteString("\n")

	return b.String()
}

func BuildAIGeneratePrompt(name, description, target string) string {
	return fmt.Sprintf(`Generate a skill file for an AI coding assistant.

SKILL NAME: %s
DESCRIPTION: %s
TARGET: %s (crush = Crush with GLM, claude = Claude Code, both = both tools)

The skill must follow this EXACT format:
1. YAML frontmatter with: name, description
2. Markdown body with detailed instructions

The skill should be practical, specific, and actionable.
Include:
- When to activate this skill
- Step-by-step instructions
- Examples where relevant
- Error handling guidance

Output ONLY the skill file content, starting with ---`, name, description, target)
}