package service

import (
	"bufio"
	"context"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"time"
	"view/model"
	"view/platform"
)

const (
	insightMaxFileSize  = 1024 * 1024
	insightMaxTotalRead = 20 * 1024 * 1024
)

// InsightService 基于既有统计快照做维护性检查。
// 它不会重新遍历整个仓库，只读取已记录的小型源码文件，用于发现 TODO、长文件等轻量风险。
type InsightService struct{}

func (InsightService) Analyze(ctx context.Context, project model.Project, structure model.StructureStats, git model.GitStats) (model.ProjectInsights, error) {
	desc, e := platform.ResolvePath(project.Path)
	if e != nil {
		return model.ProjectInsights{}, e
	}
	out := model.ProjectInsights{ProjectID: project.ID, GeneratedAt: time.Now().Format(time.RFC3339), Issues: []model.InsightIssue{}}
	add := func(issue model.InsightIssue) {
		out.Issues = append(out.Issues, issue)
		switch issue.Severity {
		case "high":
			out.Summary.High++
		case "medium":
			out.Summary.Medium++
		default:
			out.Summary.Low++
		}
	}

	checkLanguageHealth(project.Languages, add)
	out.Summary.LargeFiles = len(structure.LargeFiles)
	checkStructureHealth(structure, add)
	checkGitHealth(git, add)
	if e = scanTextMarkers(ctx, desc.WindowsPath, structure.Files, add, &out.Summary); e != nil {
		add(model.InsightIssue{Severity: "medium", Type: "scan_error", Title: "源码检查未完全完成", Detail: e.Error(), Suggestion: "检查项目目录权限，或重新执行项目统计。"})
	}

	sort.SliceStable(out.Issues, func(i, j int) bool {
		return severityRank(out.Issues[i].Severity) > severityRank(out.Issues[j].Severity)
	})
	out.HealthScore = healthScore(out.Summary)
	return out, nil
}

func checkLanguageHealth(langs []model.LanguageStat, add func(model.InsightIssue)) {
	for _, x := range langs {
		total := x.Code + x.Comments
		if x.Code < 500 || x.Files < 3 || total == 0 {
			continue
		}
		ratio := float64(x.Comments) / float64(total)
		if ratio < 0.03 {
			add(model.InsightIssue{Severity: "medium", Type: "low_comment_ratio", Title: "注释率偏低", Detail: x.Name + " 的注释占比低于 3%。", Suggestion: "为核心业务、复杂条件和公共接口补充解释性注释。"})
		} else if ratio < 0.06 {
			add(model.InsightIssue{Severity: "low", Type: "low_comment_ratio", Title: "注释率略低", Detail: x.Name + " 的注释占比低于 6%。", Suggestion: "优先补充复杂模块和团队协作频繁的文件。"})
		}
	}
}

func checkStructureHealth(s model.StructureStats, add func(model.InsightIssue)) {
	for _, f := range s.LargeFiles {
		severity := "medium"
		if f.Size >= 5*1024*1024 {
			severity = "high"
		}
		add(model.InsightIssue{Severity: severity, Type: "large_file", Title: "发现大文件", Detail: "文件体积可能影响仓库加载和代码审查。", Path: f.Path, Suggestion: "确认是否可以拆分、压缩或移动到对象存储。"})
	}
	if len(s.Folders) > 0 && s.TotalSize > 0 {
		top := s.Folders[0]
		if float64(top.Size)/float64(s.TotalSize) > 0.65 && top.Files > 20 {
			add(model.InsightIssue{Severity: "medium", Type: "folder_concentration", Title: "目录体量过于集中", Detail: top.Name + " 占据了项目大部分体积。", Path: top.Name, Suggestion: "检查该目录是否混入构建产物、缓存或可拆分模块。"})
		}
	}
	unknown := 0
	for _, x := range s.Extensions {
		if x.Extension == "" {
			unknown += int(x.Files)
		}
	}
	if unknown > 20 {
		add(model.InsightIssue{Severity: "low", Type: "unknown_files", Title: "无扩展名文件较多", Detail: "项目中存在较多无扩展名文件。", Suggestion: "确认这些文件是否都是必要脚本、配置或运行产物。"})
	}
}

func checkGitHealth(g model.GitStats, add func(model.InsightIssue)) {
	if g.CommitCount == 0 || len(g.Contributors) == 0 {
		return
	}
	top := g.Contributors[0]
	if float64(top.Commits)/float64(g.CommitCount) > 0.75 && g.CommitCount > 20 {
		add(model.InsightIssue{Severity: "medium", Type: "contributor_concentration", Title: "提交集中度较高", Detail: top.Name + " 贡献了超过 75% 的提交。", Suggestion: "关注知识分散、代码评审和关键模块交接风险。"})
	}
	for _, c := range g.Commits[:min(30, len(g.Commits))] {
		if c.Added+c.Deleted > 3000 {
			add(model.InsightIssue{Severity: "low", Type: "large_commit", Title: "近期存在大提交", Detail: c.Message, Path: c.Hash, Suggestion: "大提交建议拆分审查，降低回滚和定位问题的成本。"})
		}
	}
}

func scanTextMarkers(ctx context.Context, root string, files []model.FileEntry, add func(model.InsightIssue), summary *model.InsightSummary) error {
	totalRead := int64(0)
	for _, f := range files {
		if f.IsDir || f.Size <= 0 || f.Size > insightMaxFileSize || !isInsightTextFile(f.Extension) {
			continue
		}
		if totalRead+f.Size > insightMaxTotalRead {
			return nil
		}
		select {
		case <-ctx.Done():
			return ctx.Err()
		default:
		}
		totalRead += f.Size
		path := filepath.Join(root, filepath.FromSlash(f.Path))
		lines, markers := inspectTextFile(path)
		if lines >= 1500 {
			summary.LongFiles++
			add(model.InsightIssue{Severity: "high", Type: "long_file", Title: "文件过长", Detail: "文件超过 1500 行，理解和评审成本较高。", Path: f.Path, Suggestion: "按职责拆分模块，提取复用函数或服务。"})
		} else if lines >= 800 {
			summary.LongFiles++
			add(model.InsightIssue{Severity: "medium", Type: "long_file", Title: "文件偏长", Detail: "文件超过 800 行。", Path: f.Path, Suggestion: "关注是否存在多个职责混在同一文件中。"})
		}
		for _, issue := range markers {
			summary.TodoCount++
			issue.Path = f.Path
			add(issue)
		}
	}
	return nil
}

func inspectTextFile(path string) (int, []model.InsightIssue) {
	file, e := os.Open(path)
	if e != nil {
		return 0, nil
	}
	defer file.Close()
	scanner := bufio.NewScanner(file)
	scanner.Buffer(make([]byte, 0, 64*1024), 1024*1024)
	line := 0
	issues := []model.InsightIssue{}
	for scanner.Scan() {
		line++
		text := scanner.Text()
		upper := strings.ToUpper(text)
		kind, severity := "", "low"
		switch {
		case strings.Contains(upper, "FIXME"):
			kind, severity = "FIXME", "medium"
		case strings.Contains(upper, "HACK"):
			kind, severity = "HACK", "medium"
		case strings.Contains(upper, "TODO"):
			kind = "TODO"
		}
		if kind != "" {
			issues = append(issues, model.InsightIssue{Severity: severity, Type: "todo_marker", Title: "发现 " + kind + " 标记", Detail: "源码中存在待处理标记。", Line: line, Suggestion: "确认该标记是否仍有效，并补充负责人或处理计划。", Evidence: strings.TrimSpace(text)})
		}
	}
	return line, issues
}

func isInsightTextFile(ext string) bool {
	switch strings.ToLower(ext) {
	case ".go", ".php", ".js", ".ts", ".vue", ".jsx", ".tsx", ".css", ".scss", ".sass", ".less", ".html", ".md", ".json", ".yaml", ".yml", ".xml", ".sql", ".py", ".java", ".cs", ".rb", ".rs", ".c", ".cpp", ".h":
		return true
	default:
		return false
	}
}

func healthScore(s model.InsightSummary) int {
	score := 100 - s.High*12 - s.Medium*6 - s.Low*2
	if score < 0 {
		return 0
	}
	return score
}

func severityRank(s string) int {
	switch s {
	case "high":
		return 3
	case "medium":
		return 2
	default:
		return 1
	}
}