package prompt

import (
	"fmt"
	"io/fs"
	"os"
	"path/filepath"
	"strings"
)

// Skill 定义了从 SKILL.md 中解析出的标准化技能结构
type Skill struct {
	Name        string
	Description string
	Body        string
}

// SkillSummary 是技能的轻量目录项（仅元信息，不含 Body）
type SkillSummary struct {
	Name        string
	Description string
}

// SkillLoader 负责从本地文件系统中加载技能模板
type SkillLoader struct {
	workDir string
}

func NewSkillLoader(workDir string) *SkillLoader {
	return &SkillLoader{workDir: workDir}
}

// List 扫描 skills 目录，返回所有技能的轻量目录（仅名称和描述）
func (s *SkillLoader) List() []SkillSummary {
	skillBaseDir := filepath.Join(s.workDir, "skills")
	if _, err := os.Stat(skillBaseDir); os.IsNotExist(err) {
		return nil
	}

	var summaries []SkillSummary

	filepath.WalkDir(skillBaseDir, func(path string, d fs.DirEntry, err error) error {
		if err != nil {
			return nil
		}
		if d.IsDir() || d.Name() != "SKILL.md" {
			return nil
		}

		content, err := os.ReadFile(path)
		if err != nil {
			return nil
		}

		skill := parseSkillMD(string(content))
		summaries = append(summaries, SkillSummary{
			Name:        skill.Name,
			Description: skill.Description,
		})
		return nil
	})

	return summaries
}

// Load 按技能名称加载完整的 Skill（含 Body）
func (s *SkillLoader) Load(name string) (*Skill, error) {
	skillBaseDir := filepath.Join(s.workDir, "skills")
	if _, err := os.Stat(skillBaseDir); os.IsNotExist(err) {
		return nil, fmt.Errorf("skills 目录不存在")
	}

	var found *Skill

	filepath.WalkDir(skillBaseDir, func(path string, d fs.DirEntry, err error) error {
		if err != nil || found != nil {
			return nil
		}
		if d.IsDir() || d.Name() != "SKILL.md" {
			return nil
		}

		content, err := os.ReadFile(path)
		if err != nil {
			return nil
		}

		skill := parseSkillMD(string(content))
		if skill.Name == name {
			found = &skill
		}
		return nil
	})

	if found == nil {
		return nil, fmt.Errorf("未找到技能: %s", name)
	}
	return found, nil
}

// parseSkillMD 解析带有 YAML Frontmatter 的 Markdown 内容
func parseSkillMD(content string) Skill {
	skill := Skill{
		Name:        "Unknown Skill",
		Description: "No description provided.",
		Body:        content,
	}

	if strings.HasPrefix(content, "---\n") || strings.HasPrefix(content, "---\r\n") {
		parts := strings.SplitN(content, "---", 3)
		if len(parts) == 3 {
			frontmatter := parts[1]
			skill.Body = strings.TrimSpace(parts[2])

			lines := strings.Split(frontmatter, "\n")
			for _, line := range lines {
				line = strings.TrimSpace(line)
				if strings.HasPrefix(line, "name:") {
					skill.Name = strings.TrimSpace(strings.TrimPrefix(line, "name:"))
				} else if strings.HasPrefix(line, "description:") {
					skill.Description = strings.TrimSpace(strings.TrimPrefix(line, "description:"))
				}
			}
		}
	}

	return skill
}