package git

import (
	"math"
	"os"
	"path/filepath"
	"testing"
	"time"

	gogit "github.com/go-git/go-git/v5"
	"github.com/go-git/go-git/v5/plumbing/object"
)

// commitLanguageFiles creates real Git objects, including bare-mirror compatible trees.
func commitLanguageFiles(t *testing.T, files map[string]string) (string, *gogit.Repository) {
	t.Helper()
	path := t.TempDir()
	repo, err := gogit.PlainInit(path, false)
	if err != nil {
		t.Fatal(err)
	}
	wt, err := repo.Worktree()
	if err != nil {
		t.Fatal(err)
	}
	for name, content := range files {
		target := filepath.Join(path, name)
		if err := os.MkdirAll(filepath.Dir(target), 0755); err != nil {
			t.Fatal(err)
		}
		if err := os.WriteFile(target, []byte(content), 0644); err != nil {
			t.Fatal(err)
		}
		if _, err := wt.Add(name); err != nil {
			t.Fatal(err)
		}
	}
	author := &object.Signature{Name: "Test Author", Email: "author@example.com", When: time.Now()}
	if _, err := wt.Commit("Language fixtures", &gogit.CommitOptions{Author: author}); err != nil {
		t.Fatal(err)
	}
	return path, repo
}

func TestLanguagesSourceBytesAndExclusions(t *testing.T) {
	files := map[string]string{
		"main.go":                   "package main\n\nfunc main() {}\n",
		"lib/helpers.go":            "package main\n\nconst answer = 42\n",
		"src/index.js":              "export const answer = 42;\n",
		"page.html":                 "<!doctype html><html><body>Hello</body></html>\n",
		"README.md":                 "# Documentation\n",
		"data.json":                 "{\"name\":\"data\"}",
		"settings.yaml":             "enabled: true\n",
		"binary.go":                 "\x00\x01\x02not source",
		"empty.py":                  "",
		"vendor/dep/code.go":        "package dependency\n",
		"node_modules/pkg/index.js": "export const dependency = true;\n",
		"generated.go":              "// Code generated by a tool. DO NOT EDIT.\npackage main\n",
	}
	path, _ := commitLanguageFiles(t, files)
	if err := os.Symlink("main.go", filepath.Join(path, "alias.py")); err != nil {
		t.Fatal(err)
	}
	repo, err := gogit.PlainOpen(path)
	if err != nil {
		t.Fatal(err)
	}
	wt, err := repo.Worktree()
	if err != nil {
		t.Fatal(err)
	}
	if _, err := wt.Add("alias.py"); err != nil {
		t.Fatal(err)
	}
	if _, err := wt.Commit("Add source link", &gogit.CommitOptions{Author: &object.Signature{Name: "Test", Email: "test@example.com", When: time.Now()}}); err != nil {
		t.Fatal(err)
	}
	g, err := Open(path, "")
	if err != nil {
		t.Fatal(err)
	}
	stats, err := g.Languages()
	if err != nil {
		t.Fatal(err)
	}
	want := map[string]int64{"Go": int64(len(files["main.go"]) + len(files["lib/helpers.go"])), "JavaScript": int64(len(files["src/index.js"])), "HTML": int64(len(files["page.html"]))}
	if len(stats) != len(want) {
		t.Fatalf("languages: %+v; want %v", stats, want)
	}
	var total int64
	for _, size := range want {
		total += size
	}
	for i, stat := range stats {
		if stat.Bytes != want[stat.Name] {
			t.Errorf("%s: %d bytes, want %d", stat.Name, stat.Bytes, want[stat.Name])
		}
		percentage := 100 * float64(want[stat.Name]) / float64(total)
		if math.Abs(stat.Percentage-percentage) > 1e-8 {
			t.Errorf("%s: percentage %f, want %f", stat.Name, stat.Percentage, percentage)
		}
		if i > 0 && stat.Bytes > stats[i-1].Bytes {
			t.Error("languages are not sorted by code size")
		}
	}
	// Mirrors have no working tree but must produce the same statistics.
	barePath := filepath.Join(t.TempDir(), "mirror.git")
	if _, err := gogit.PlainClone(barePath, true, &gogit.CloneOptions{URL: path}); err != nil {
		t.Fatal(err)
	}
	bare, err := Open(barePath, "")
	if err != nil {
		t.Fatal(err)
	}
	bareStats, err := bare.Languages()
	if err != nil {
		t.Fatal(err)
	}
	if len(bareStats) != len(stats) {
		t.Fatalf("bare mirror statistics: %+v", bareStats)
	}
}

func TestLanguagesCacheFollowsCommits(t *testing.T) {
	path, repo := commitLanguageFiles(t, map[string]string{"main.go": "package main\n"})
	g, err := Open(path, "")
	if err != nil {
		t.Fatal(err)
	}
	before, err := g.Languages()
	if err != nil {
		t.Fatal(err)
	}
	if len(before) != 1 || before[0].Name != "Go" {
		t.Fatalf("initial languages: %+v", before)
	}
	before[0].Name = "mutated"
	cached, err := g.Languages()
	if err != nil {
		t.Fatal(err)
	}
	if cached[0].Name != "Go" {
		t.Fatal("caller modified the cached statistics")
	}
	if err := os.WriteFile(filepath.Join(path, "main.py"), []byte("print('new language')\n"), 0644); err != nil {
		t.Fatal(err)
	}
	wt, err := repo.Worktree()
	if err != nil {
		t.Fatal(err)
	}
	if _, err := wt.Add("main.py"); err != nil {
		t.Fatal(err)
	}
	if _, err := wt.Commit("Add Python", &gogit.CommitOptions{Author: &object.Signature{Name: "Test", Email: "test@example.com", When: time.Now()}}); err != nil {
		t.Fatal(err)
	}
	updated, err := Open(path, "")
	if err != nil {
		t.Fatal(err)
	}
	after, err := updated.Languages()
	if err != nil {
		t.Fatal(err)
	}
	if len(after) != 2 || after[0].Name != "Python" {
		t.Fatalf("new commit did not refresh statistics: %+v", after)
	}
}

func TestLanguagesDocumentationOnly(t *testing.T) {
	path, _ := commitLanguageFiles(t, map[string]string{"README.md": "# Just documentation\n"})
	g, err := Open(path, "")
	if err != nil {
		t.Fatal(err)
	}
	stats, err := g.Languages()
	if err != nil {
		t.Fatal(err)
	}
	if len(stats) != 0 {
		t.Fatalf("documentation counted as source: %+v", stats)
	}
}