// Package service 实现代码扫描、Git 分析和后台任务等业务能力。
package service

import (
	"context"
	"errors"
	"fmt"
	"github.com/hhatto/gocloc"
	gitignore "github.com/sabhiram/go-gitignore"
	"io/fs"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"view/model"
	"view/platform"
)

// Scanner 负责遍历项目、应用排除规则并调用 gocloc 统计代码。它不依赖 Wails，可独立测试。
type Scanner struct{}

// MatchExcludedPattern 对目录的每一级名称应用通配符，并对带斜杠的规则匹配完整相对路径。
func MatchExcludedPattern(pattern, rel string) bool {
	pattern = filepath.ToSlash(strings.TrimSpace(pattern))
	rel = filepath.ToSlash(rel)
	if strings.Contains(pattern, "/") {
		ok, _ := filepath.Match(filepath.FromSlash(pattern), filepath.FromSlash(rel))
		return ok
	}
	for _, part := range strings.Split(rel, "/") {
		if ok, _ := filepath.Match(pattern, part); ok {
			return true
		}
	}
	return false
}

// Analyze 同时支持普通 Windows 路径与 WSL UNC 路径。WSL 文件通过 UNC 读取，Git 则由 GitService 在发行版内部执行。
func (Scanner) Analyze(ctx context.Context, root string, rules []model.ExclusionRule, progress func(int, string)) ([]model.LanguageStat, []model.FileEntry, error) {
	desc, e := platform.ResolvePath(root)
	if e != nil {
		return nil, nil, e
	}
	root = desc.WindowsPath
	// WalkDir 对根目录回调错误若被忽略会得到“0 文件但成功”的假结果，因此分析前必须验证根目录。
	if info, statErr := os.Stat(root); statErr != nil {
		if desc.WSL {
			return nil, nil, &platform.PlatformError{Code: "WSL_PATH_UNAVAILABLE", Detail: statErr.Error()}
		}
		return nil, nil, statErr
	} else if !info.IsDir() {
		return nil, nil, errors.New("PROJECT_PATH_NOT_DIRECTORY")
	}
	// 每份 .gitignore 只控制其所在目录及后代。不能预先收集后再全局匹配，
	// 否则 vendor 等依赖目录中的局部通配符会错误排除项目根目录的源码。
	type scopedIgnore struct {
		base    string
		matcher *gitignore.GitIgnore
	}
	ignores := []scopedIgnore{}
	addIgnore := func(dir, base string) {
		matcher, compileErr := gitignore.CompileIgnoreFile(filepath.Join(dir, ".gitignore"))
		if compileErr == nil {
			ignores = append(ignores, scopedIgnore{base: filepath.ToSlash(base), matcher: matcher})
		}
	}
	excluded := func(rel string) bool {
		slash := filepath.ToSlash(rel)
		for _, r := range rules {
			if MatchExcludedPattern(r.Pattern, slash) {
				return true
			}
		}
		for _, scoped := range ignores {
			local := slash
			if scoped.base != "." && scoped.base != "" {
				prefix := strings.TrimSuffix(scoped.base, "/") + "/"
				if !strings.HasPrefix(slash, prefix) {
					continue
				}
				local = strings.TrimPrefix(slash, prefix)
			}
			if scoped.matcher.MatchesPath(local) || scoped.matcher.MatchesPath("/"+local) {
				return true
			}
		}
		return false
	}
	files := []model.FileEntry{}
	codeFiles := []string{}
	count := 0
	e = filepath.WalkDir(root, func(path string, d fs.DirEntry, err error) error {
		if err != nil {
			if path == root {
				return err
			}
			return nil
		}
		select {
		case <-ctx.Done():
			return ctx.Err()
		default:
		}
		if path == root {
			addIgnore(root, ".")
			return nil
		}
		rel, x := filepath.Rel(root, path)
		if x != nil {
			return nil
		}
		if d.Type()&os.ModeSymlink != 0 {
			if d.IsDir() {
				return filepath.SkipDir
			}
			return nil
		}
		if excluded(rel) {
			if d.IsDir() {
				return filepath.SkipDir
			}
			return nil
		}
		if d.IsDir() {
			addIgnore(path, rel)
		}
		info, x := d.Info()
		if x != nil {
			return nil
		}
		entry := model.FileEntry{Path: filepath.ToSlash(rel), Name: d.Name(), Extension: strings.ToLower(filepath.Ext(d.Name())), Size: info.Size(), IsDir: d.IsDir(), Parent: filepath.ToSlash(filepath.Dir(rel))}
		files = append(files, entry)
		if !d.IsDir() {
			count++
			ext := strings.TrimPrefix(entry.Extension, ".")
			if _, ok := gocloc.Exts[ext]; ok {
				codeFiles = append(codeFiles, path)
			}
			if count%250 == 0 {
				progress(min(65, 10+count/50), "task.scan")
			}
		}
		return nil
	})
	if e != nil {
		return nil, nil, e
	}
	progress(70, "task.count")
	defs := gocloc.NewDefinedLanguages()
	opts := gocloc.NewClocOptions()
	totals := map[string]*model.LanguageStat{}
	for i, path := range codeFiles {
		select {
		case <-ctx.Done():
			return nil, nil, ctx.Err()
		default:
		}
		ext := strings.TrimPrefix(strings.ToLower(filepath.Ext(path)), ".")
		name := gocloc.Exts[ext]
		lang := defs.Langs[name]
		if lang == nil {
			continue
		}
		cf, parseErr := analyzeFileSafe(path, lang, opts)
		if parseErr != nil {
			continue
		}
		x := totals[name]
		if x == nil {
			x = &model.LanguageStat{Name: name}
			totals[name] = x
		}
		x.Files++
		x.Code += int64(cf.Code)
		x.Comments += int64(cf.Comments)
		x.Blanks += int64(cf.Blanks)
		if i%100 == 0 {
			progress(70+min(25, i*25/max(1, len(codeFiles))), "task.count")
		}
	}
	langs := make([]model.LanguageStat, 0, len(totals))
	for _, x := range totals {
		langs = append(langs, *x)
	}
	sort.Slice(langs, func(i, j int) bool { return langs[i].Code > langs[j].Code })
	progress(98, "task.save")
	return langs, files, nil
}

// analyzeFileSafe 隔离第三方语言解析器的单文件异常。某个特殊源码不能影响整个桌面进程和其他文件统计。
func analyzeFileSafe(path string, lang *gocloc.Language, opts *gocloc.ClocOptions) (result *gocloc.ClocFile, err error) {
	defer func() {
		if r := recover(); r != nil {
			err = fmt.Errorf("CODE_FILE_PARSE_PANIC: %s: %v", path, r)
		}
	}()
	return gocloc.AnalyzeFile(path, lang, opts), nil
}