package browser

import (
	"fmt"
	"testing"
	"time"
)

// --- Test helpers ---

func newUnsortedEntries() []Entry {
	return []Entry{
		{Name: "Zebra.txt", Size: 1000, ModTime: time.Date(2024, 1, 15, 0, 0, 0, 0, time.UTC), IsDir: false},
		{Name: "apple.txt", Size: 500, ModTime: time.Date(2024, 3, 1, 0, 0, 0, 0, time.UTC), IsDir: false},
		{Name: "MyDir", Size: 0, ModTime: time.Date(2024, 2, 10, 0, 0, 0, 0, time.UTC), IsDir: true},
		{Name: "banana.txt", Size: 2000, ModTime: time.Date(2024, 1, 1, 0, 0, 0, 0, time.UTC), IsDir: false},
		{Name: "Cherry.txt", Size: 1500, ModTime: time.Date(2024, 2, 20, 0, 0, 0, 0, time.UTC), IsDir: false},
		{Name: "adir", Size: 0, ModTime: time.Date(2024, 1, 10, 0, 0, 0, 0, time.UTC), IsDir: true},
		{Name: "123.txt", Size: 300, ModTime: time.Date(2024, 4, 1, 0, 0, 0, 0, time.UTC), IsDir: false},
	}
}

// --- Sort Mode: Name Ascending ---

func TestSort_NameAscending(t *testing.T) {
	entries := newUnsortedEntries()
	sortEntries(entries, SortModeNameAsc)

	// Directories and files interleaved by name
	// Expected: 123.txt, adir, apple.txt, banana.txt, Cherry.txt, MyDir, Zebra.txt
	wantNames := []string{"123.txt", "adir", "apple.txt", "banana.txt", "Cherry.txt", "MyDir", "Zebra.txt"}
	for i, want := range wantNames {
		if entries[i].Name != want {
			t.Errorf("entries[%d].Name = %q, want %q", i, entries[i].Name, want)
		}
	}
}

func TestSort_NameAscending_DirsInterleaved(t *testing.T) {
	entries := newUnsortedEntries()
	sortEntries(entries, SortModeNameAsc)

	// Directories should be interleaved with files at their alphabetical position
	// adir should be between 123.txt and apple.txt
	adirIdx := -1
	for i, e := range entries {
		if e.Name == "adir" {
			adirIdx = i
			break
		}
	}
	if adirIdx <= 0 || adirIdx >= len(entries)-1 {
		t.Errorf("adir at idx %d should be between 123.txt and apple.txt", adirIdx)
	}
	// Verify neighbors
	if entries[adirIdx-1].Name != "123.txt" {
		t.Errorf("expected 123.txt before adir, got %s", entries[adirIdx-1].Name)
	}
	if entries[adirIdx+1].Name != "apple.txt" {
		t.Errorf("expected apple.txt after adir, got %s", entries[adirIdx+1].Name)
	}
}

func TestSort_NameAscending_CaseInsensitive(t *testing.T) {
	entries := newUnsortedEntries()
	sortEntries(entries, SortModeNameAsc)

	// "apple.txt" should come before "Cherry.txt" (case-insensitive)
	appleIdx := -1
	cherryIdx := -1
	for i, e := range entries {
		if e.Name == "apple.txt" {
			appleIdx = i
		}
		if e.Name == "Cherry.txt" {
			cherryIdx = i
		}
	}
	if appleIdx >= cherryIdx {
		t.Errorf("apple.txt (idx %d) should come before Cherry.txt (idx %d)", appleIdx, cherryIdx)
	}
}

func TestSort_NameAscending_NumericFirst(t *testing.T) {
	entries := newUnsortedEntries()
	sortEntries(entries, SortModeNameAsc)

	// "123.txt" should be the first entry (numbers sort before letters)
	if entries[0].Name != "123.txt" {
		t.Errorf("expected 123.txt first, got %s", entries[0].Name)
	}
}

// --- Sort Mode: Name Descending ---

func TestSort_NameDescending(t *testing.T) {
	entries := newUnsortedEntries()
	sortEntries(entries, SortModeNameDesc)

	// Directories and files interleaved by name (reverse)
	// Expected: Zebra.txt, MyDir, Cherry.txt, banana.txt, apple.txt, adir, 123.txt
	wantNames := []string{"Zebra.txt", "MyDir", "Cherry.txt", "banana.txt", "apple.txt", "adir", "123.txt"}
	for i, want := range wantNames {
		if entries[i].Name != want {
			t.Errorf("entries[%d].Name = %q, want %q", i, entries[i].Name, want)
		}
	}
}

// --- Sort Mode: Date Ascending ---

func TestSort_DateAscending(t *testing.T) {
	entries := newUnsortedEntries()
	sortEntries(entries, SortModeDateAsc)

	// Directories and files interleaved by date
	// banana.txt: 2024-01-01, adir: 2024-01-10, Zebra.txt: 2024-01-15, MyDir: 2024-02-10, Cherry.txt: 2024-02-20, apple.txt: 2024-03-01, 123.txt: 2024-04-01
	wantNames := []string{"banana.txt", "adir", "Zebra.txt", "MyDir", "Cherry.txt", "apple.txt", "123.txt"}
	for i, want := range wantNames {
		if entries[i].Name != want {
			t.Errorf("entries[%d].Name = %q, want %q", i, entries[i].Name, want)
		}
	}
}

func TestSort_DateAscending_DirsInterleaved(t *testing.T) {
	entries := newUnsortedEntries()
	sortEntries(entries, SortModeDateAsc)

	// Directories should be interleaved with files at their date position
	// adir (2024-01-10) should be between banana.txt (2024-01-01) and Zebra.txt (2024-01-15)
	adirIdx := -1
	for i, e := range entries {
		if e.Name == "adir" {
			adirIdx = i
			break
		}
	}
	if adirIdx <= 0 || adirIdx >= len(entries)-1 {
		t.Errorf("adir at idx %d should be between banana.txt and Zebra.txt", adirIdx)
	}
	if entries[adirIdx-1].Name != "banana.txt" {
		t.Errorf("expected banana.txt before adir, got %s", entries[adirIdx-1].Name)
	}
	if entries[adirIdx+1].Name != "Zebra.txt" {
		t.Errorf("expected Zebra.txt after adir, got %s", entries[adirIdx+1].Name)
	}
}

// --- Sort Mode: Date Descending ---

func TestSort_DateDescending(t *testing.T) {
	entries := newUnsortedEntries()
	sortEntries(entries, SortModeDateDesc)

	// Directories and files interleaved by date (reverse)
	wantNames := []string{"123.txt", "apple.txt", "Cherry.txt", "MyDir", "Zebra.txt", "adir", "banana.txt"}
	for i, want := range wantNames {
		if entries[i].Name != want {
			t.Errorf("entries[%d].Name = %q, want %q", i, entries[i].Name, want)
		}
	}
}

// --- Sort Mode: Size Ascending (REMOVED - only 4 sort modes: name +/-, date +/-) ---
// Size-based sorting has been removed from the browser to keep sort modes minimal.
// The sortEntries function still exists for potential future use.

// --- Sort Mode: Size Descending (REMOVED - only 4 sort modes: name +/-, date +/-) ---
// Size-based sorting has been removed from the browser to keep sort modes minimal.
// The sortEntries function still exists for potential future use.

// --- Edge Cases ---

func TestSort_EmptySlice(t *testing.T) {
	var entries []Entry
	sortEntries(entries, SortModeNameAsc)
	if len(entries) != 0 {
		t.Errorf("expected empty slice, got %d entries", len(entries))
	}
}

func TestSort_SingleEntry(t *testing.T) {
	entries := []Entry{{Name: "only.txt", Size: 100, IsDir: false}}
	sortEntries(entries, SortModeNameAsc)
	if len(entries) != 1 || entries[0].Name != "only.txt" {
		t.Errorf("single entry sort failed: %v", entries)
	}
}

func TestSort_AllDirectories(t *testing.T) {
	entries := []Entry{
		{Name: "Zdir", IsDir: true},
		{Name: "adir", IsDir: true},
		{Name: "Mdir", IsDir: true},
	}
	sortEntries(entries, SortModeNameAsc)
	wantNames := []string{"adir", "Mdir", "Zdir"}
	for i, want := range wantNames {
		if entries[i].Name != want {
			t.Errorf("entries[%d].Name = %q, want %q", i, entries[i].Name, want)
		}
	}
}

func TestSort_AllFiles(t *testing.T) {
	entries := []Entry{
		{Name: "Zebra.txt", IsDir: false},
		{Name: "apple.txt", IsDir: false},
		{Name: "Mango.txt", IsDir: false},
	}
	sortEntries(entries, SortModeNameAsc)
	wantNames := []string{"apple.txt", "Mango.txt", "Zebra.txt"}
	for i, want := range wantNames {
		if entries[i].Name != want {
			t.Errorf("entries[%d].Name = %q, want %q", i, entries[i].Name, want)
		}
	}
}

func TestSort_StableEqualKeys(t *testing.T) {
	// When two entries have equal sort keys, order should be deterministic
	entries := []Entry{
		{Name: "bbb.txt", Size: 100, ModTime: time.Date(2024, 1, 1, 0, 0, 0, 0, time.UTC), IsDir: false},
		{Name: "aaa.txt", Size: 100, ModTime: time.Date(2024, 1, 1, 0, 0, 0, 0, time.UTC), IsDir: false},
	}
	sortEntries(entries, SortModeNameAsc)
	// Same name — should maintain stable order
	if entries[0].Name != "aaa.txt" {
		t.Errorf("expected aaa.txt first on equal name, got %s", entries[0].Name)
	}
}

func TestSort_NoSideEffectsOnOriginalOrder(t *testing.T) {
	// Sorting should not corrupt entry data
	entries := newUnsortedEntries()
	originalNames := make([]string, len(entries))
	for i, e := range entries {
		originalNames[i] = e.Name
	}

	sortEntries(entries, SortModeNameAsc)

	// All original entries should still be present
	names := make(map[string]bool)
	for _, e := range entries {
		names[e.Name] = true
	}
	for _, name := range originalNames {
		if !names[name] {
			t.Errorf("entry %q lost during sort", name)
		}
	}
}

func TestSort_InvalidMode(t *testing.T) {
	entries := newUnsortedEntries()
	originalLen := len(entries)

	// Invalid mode should not panic and should leave entries intact
	sortEntries(entries, SortMode(-99))

	if len(entries) != originalLen {
		t.Errorf("invalid mode changed entry count: %d -> %d", originalLen, len(entries))
	}
}

func TestSort_LargeSlice(t *testing.T) {
	const count = 10000
	entries := make([]Entry, count)
	for i := 0; i < count; i++ {
		entries[i] = Entry{
			Name:    fmt.Sprintf("file_%05d.txt", i),
			Size:    int64(i * 10),
			ModTime: time.Date(2024, 1, 1, 0, 0, 0, 0, time.UTC).Add(time.Duration(i) * time.Hour),
			IsDir:   i%100 == 0,
		}
	}

	start := time.Now()
	sortEntries(entries, SortModeNameAsc)
	elapsed := time.Since(start)

	if elapsed > 5*time.Second {
		t.Errorf("sort took %v, expected < 5s", elapsed)
	}

	// Verify directories are interleaved (not separated)
	// With 100 entries per 100 entries being dirs, they should be mixed
	hasDirBeforeFile := false
	hasFileBeforeDir := false
	for i := 0; i < len(entries)-1; i++ {
		if entries[i].IsDir && !entries[i+1].IsDir {
			hasDirBeforeFile = true
		}
		if !entries[i].IsDir && entries[i+1].IsDir {
			hasFileBeforeDir = true
		}
	}
	if !hasDirBeforeFile || !hasFileBeforeDir {
		t.Errorf("directories should be interleaved with files, not separated")
	}
}