package fetch

import (
	"os"
	"path/filepath"
	"sort"
	"testing"
)

func TestPrettifyName_RestoresSpaces(t *testing.T) {
	got := prettifyName("01 - The_Law_of_Gravitation.mp3")
	if got != "01 - The Law of Gravitation.mp3" {
		t.Errorf("got %q", got)
	}
}

// yt-dlp's --restrict-filenames collapses odd characters into underscores, and
// replacing them can leave runs of spaces behind.
func TestPrettifyName_CollapsesRepeatedSpaces(t *testing.T) {
	got := prettifyName("02 - A___Gap.mp3")
	if got != "02 - A Gap.mp3" {
		t.Errorf("got %q", got)
	}
}

// Sources whose titles already begin with a track number produce
// "01 - 01 - April.mp3" once the output template prepends its own index. Seen
// for real against a LibriVox collection on the first live run.
func TestPrettifyName_CollapsesDuplicatedTrackPrefix(t *testing.T) {
	cases := []struct{ in, want string }{
		{"01 - 01 - April.mp3", "01 - April.mp3"},
		{"02 - 02 - Ave Atque Vale.mp3", "02 - Ave Atque Vale.mp3"},
		{"03 - 03_-_The_Average_Man.mp3", "03 - The Average Man.mp3"},
		{"10 - 10 - Tenth.mp3", "10 - Tenth.mp3"},
	}
	for _, c := range cases {
		if got := prettifyName(c.in); got != c.want {
			t.Errorf("prettifyName(%q) = %q, want %q", c.in, got, c.want)
		}
	}
}

// Only collapse when the two numbers agree. A title that genuinely starts with
// a different number is not a duplicated prefix and must be left alone.
func TestPrettifyName_KeepsDistinctLeadingNumbers(t *testing.T) {
	cases := []struct{ in, want string }{
		{"01 - 1964 - The Messenger Lectures.mp3", "01 - 1964 - The Messenger Lectures.mp3"},
		{"05 - 12 Angry Men.mp3", "05 - 12 Angry Men.mp3"},
	}
	for _, c := range cases {
		if got := prettifyName(c.in); got != c.want {
			t.Errorf("prettifyName(%q) = %q, want %q", c.in, got, c.want)
		}
	}
}

func TestPrettifyName_LeavesCleanNamesAlone(t *testing.T) {
	for _, n := range []string{"01 - April.mp3", "Introduction.mp3"} {
		if got := prettifyName(n); got != n {
			t.Errorf("prettifyName(%q) = %q, want it unchanged", n, got)
		}
	}
}

func TestRename_RenamesOnDisk(t *testing.T) {
	dir := t.TempDir()
	for _, n := range []string{"01 - 01 - April.mp3", "02 - The_Average_Man.mp3", ".podkit-archive"} {
		if err := os.WriteFile(filepath.Join(dir, n), []byte("x"), 0o644); err != nil {
			t.Fatal(err)
		}
	}

	if _, err := Rename(dir); err != nil {
		t.Fatalf("Rename: %v", err)
	}

	entries, _ := os.ReadDir(dir)
	var names []string
	for _, e := range entries {
		names = append(names, e.Name())
	}
	sort.Strings(names)

	want := []string{".podkit-archive", "01 - April.mp3", "02 - The Average Man.mp3"}
	if len(names) != len(want) {
		t.Fatalf("got %v, want %v", names, want)
	}
	for i := range want {
		if names[i] != want[i] {
			t.Errorf("got %v, want %v", names, want)
			break
		}
	}
}

// Renaming must never destroy an existing file to make a name prettier.
func TestRename_DoesNotClobber(t *testing.T) {
	dir := t.TempDir()
	if err := os.WriteFile(filepath.Join(dir, "01 - April.mp3"), []byte("original"), 0o644); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(filepath.Join(dir, "01 - 01 - April.mp3"), []byte("candidate"), 0o644); err != nil {
		t.Fatal(err)
	}

	if _, err := Rename(dir); err != nil {
		t.Fatalf("Rename: %v", err)
	}

	body, err := os.ReadFile(filepath.Join(dir, "01 - April.mp3"))
	if err != nil {
		t.Fatal(err)
	}
	if string(body) != "original" {
		t.Error("an existing file was overwritten by the rename")
	}
}

func TestRename_MissingDirectoryIsAnError(t *testing.T) {
	if _, err := Rename(filepath.Join(t.TempDir(), "nope")); err == nil {
		t.Error("expected an error for a missing directory")
	}
}

// Check must explain what to install, not just report a lookup failure.
func TestErrNotInstalled_SaysHowToFixIt(t *testing.T) {
	e := &ErrNotInstalled{}
	for _, want := range []string{"yt-dlp", "pip install", "ffmpeg"} {
		if !contains(e.Error(), want) {
			t.Errorf("error message should mention %q; got %q", want, e.Error())
		}
	}
}

func contains(h, n string) bool {
	return len(h) >= len(n) && (func() bool {
		for i := 0; i+len(n) <= len(h); i++ {
			if h[i:i+len(n)] == n {
				return true
			}
		}
		return false
	})()
}