package knowledge

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

type Skill struct {
	Name    string
	Content string
	Source  string
}

type SkillSummary struct {
	DirName     string
	Name        string
	Description string
	Source      string
}

type scannedSkill struct {
	dirName     string
	name        string
	description string
	content     string
	source      string
}

func LoadSoul(path string) (string, error) {
	b, err := os.ReadFile(path)
	if err != nil {
		return "", fmt.Errorf("read soul file failed: %w", err)
	}
	content := strings.TrimSpace(string(b))
	if content == "" {
		return "", fmt.Errorf("soul file is empty")
	}
	return content, nil
}

func LoadSkillSet(dir string) ([]Skill, error) {
	scanned, err := scanSkills(dir)
	if err != nil {
		return nil, err
	}
	out := make([]Skill, 0, len(scanned))
	for _, s := range scanned {
		out = append(out, Skill{
			Name:    s.name,
			Content: s.content,
			Source:  s.source,
		})
	}
	return out, nil
}

func LoadSkillSummaries(dir string) ([]SkillSummary, error) {
	scanned, err := scanSkills(dir)
	if err != nil {
		return nil, err
	}
	out := make([]SkillSummary, 0, len(scanned))
	for _, s := range scanned {
		out = append(out, SkillSummary{
			DirName:     s.dirName,
			Name:        s.name,
			Description: s.description,
			Source:      s.source,
		})
	}
	return out, nil
}

func scanSkills(dir string) ([]scannedSkill, error) {
	entries, err := os.ReadDir(dir)
	if err != nil {
		return nil, fmt.Errorf("read skills dir failed: %w", err)
	}

	skillDirs := make([]string, 0)
	for _, entry := range entries {
		if entry.IsDir() {
			skillDirs = append(skillDirs, entry.Name())
		}
	}
	sort.Strings(skillDirs)

	out := make([]scannedSkill, 0, len(skillDirs))
	for _, skillDir := range skillDirs {
		file := filepath.Join(dir, skillDir, "skill.md")
		b, err := os.ReadFile(file)
		if err != nil {
			if os.IsNotExist(err) {
				continue
			}
			return nil, fmt.Errorf("read skill file failed: %w", err)
		}
		content := strings.TrimSpace(string(b))
		if content == "" {
			continue
		}
		name, description := parseSkillNameDescription(skillDir, content)
		if strings.TrimSpace(name) == "" {
			continue
		}
		out = append(out, scannedSkill{
			dirName:     skillDir,
			name:        name,
			description: description,
			content:     content,
			source:      file,
		})
	}

	if len(out) == 0 {
		return nil, fmt.Errorf("no valid skills loaded from %s (expected: skills/<skill_name>/skill.md)", dir)
	}
	return out, nil
}

func extractSkillName(fileName, markdown string) string {
	for _, line := range strings.Split(markdown, "\n") {
		line = strings.TrimSpace(line)
		if !strings.HasPrefix(line, "#") {
			continue
		}
		title := strings.TrimSpace(strings.TrimLeft(line, "#"))
		title = strings.TrimSpace(strings.TrimPrefix(title, "Skill:"))
		title = strings.TrimSpace(strings.TrimPrefix(title, "skill:"))
		if title != "" {
			return title
		}
	}
	base := strings.TrimSuffix(fileName, filepath.Ext(fileName))
	if base == "" {
		return fileName
	}
	return base
}

func parseSkillNameDescription(fileName, markdown string) (string, string) {
	name := ""
	description := ""
	fm := parseFrontMatter(markdown)
	if v, ok := fm["name"]; ok {
		name = strings.TrimSpace(v)
	}
	if v, ok := fm["description"]; ok {
		description = strings.TrimSpace(v)
	}
	if name == "" {
		name = extractSkillName(fileName, markdown)
	}
	if description == "" {
		description = extractSkillDescription(markdown)
	}
	return name, description
}

func parseFrontMatter(markdown string) map[string]string {
	lines := strings.Split(markdown, "\n")
	out := map[string]string{}
	if len(lines) < 3 {
		return out
	}
	if strings.TrimSpace(lines[0]) != "---" {
		return out
	}
	for i := 1; i < len(lines); i++ {
		line := strings.TrimSpace(lines[i])
		if line == "---" {
			break
		}
		idx := strings.Index(line, ":")
		if idx <= 0 {
			continue
		}
		k := strings.ToLower(strings.TrimSpace(line[:idx]))
		v := strings.TrimSpace(line[idx+1:])
		v = strings.Trim(v, "\"'")
		if k != "" && v != "" {
			out[k] = v
		}
	}
	return out
}

func extractSkillDescription(markdown string) string {
	lines := strings.Split(markdown, "\n")
	for _, raw := range lines {
		line := strings.TrimSpace(raw)
		if line == "" || strings.HasPrefix(line, "#") || strings.HasPrefix(line, "---") {
			continue
		}
		if strings.Contains(line, ":") {
			parts := strings.SplitN(line, ":", 2)
			if len(parts) == 2 {
				left := strings.ToLower(strings.TrimSpace(parts[0]))
				if left == "name" || left == "description" || left == "source" || left == "generated_at" {
					continue
				}
			}
		}
		if len(line) > 200 {
			line = line[:200]
		}
		return line
	}
	return ""
}