package iox

import (
	"io/fs"
	"reflect"
	"sort"
	"testing"
	"testing/fstest"
)

func setupFS() fs.ReadDirFS {
	// Create an in-memory FS with a mix of files and directories
	return fstest.MapFS{
		"main.go":           &fstest.MapFile{Data: []byte("package main")},
		"main_test.go":      &fstest.MapFile{Data: []byte("package main_test")},
		"README.md":         &fstest.MapFile{Data: []byte("# readme")},
		"LICENSE":           &fstest.MapFile{Data: []byte("MIT")},
		"docs/guide.md":     &fstest.MapFile{Data: []byte("Docs")},
		"docs/other.txt":    &fstest.MapFile{Data: []byte("Other")},
		"docs/hidden/.keep": &fstest.MapFile{Data: []byte("")},
		"assets/img.png":    &fstest.MapFile{Data: []byte("PNG")},
		"assets/style.css":  &fstest.MapFile{Data: []byte("CSS")},
		".gitignore":        &fstest.MapFile{Data: []byte("*.log")},
		".hiddenfile":       &fstest.MapFile{Data: []byte("")},
		"emptydir/":         &fstest.MapFile{Mode: fs.ModeDir},
	}
}

// helper to get base names for easier comparison
func basenames(entries []fs.DirEntry) []string {
	names := []string{}
	for _, e := range entries {
		names = append(names, e.Name())
	}
	sort.Strings(names)
	return names
}

func TestGlobFSMultiplePatterns(t *testing.T) {
	memfs := setupFS()
	gfs := NewGlobFS(memfs, "*.go", "*.md", "assets/*", "docs/guide.md", ".gitignore")

	tests := []struct {
		path    string
		want    []string
		wantErr bool
	}{
		{path: ".", want: []string{"README.md", "assets", "docs", "main.go", "main_test.go", ".gitignore"}},
		{path: "assets", want: []string{"img.png", "style.css"}},
		{path: "docs", want: []string{"guide.md"}},
		{path: "docs/hidden", want: []string{}, wantErr: true},
		{path: "emptydir", want: []string{}, wantErr: true},
	}

	for _, tc := range tests {
		tc := tc // capture range variable
		t.Run(tc.path, func(t *testing.T) {
			entries, err := fs.ReadDir(gfs, tc.path)
			if tc.wantErr && err == nil {
				t.Errorf("expected error, got nil")
				return
			}
			if !tc.wantErr && err != nil {
				t.Errorf("unexpected error: %v", err)
				return
			}
			got := basenames(entries)
			sort.Strings(tc.want)
			if !reflect.DeepEqual(got, tc.want) {
				t.Errorf("got %v; want %v", got, tc.want)
			}
		})
	}
}

func TestGlobFSOpen(t *testing.T) {
	memfs := setupFS()
	gfs := NewGlobFS(memfs, "*.go", "*.md", "assets/*", "docs/guide.md", ".gitignore")

	type test struct {
		path    string
		wantErr bool
	}
	tests := []test{
		{path: "main.go"},
		{path: "README.md"},
		{path: "LICENSE", wantErr: true},
		{path: "assets/img.png"},
		{path: "assets/style.css"},
		{path: "assets/nonexistent.png", wantErr: true},
		{path: "docs/guide.md"},
		{path: "docs/other.txt", wantErr: true},
		{path: ".gitignore"},
		{path: ".hiddenfile", wantErr: true},
		{path: "docs/hidden/.keep", wantErr: true},
		{path: "emptydir", wantErr: true},
		{path: "docs"},   // allowed because it contains matching file(s)
		{path: "assets"}, // allowed because it contains matching file(s)
	}
	for _, tc := range tests {
		tc := tc
		t.Run(tc.path, func(t *testing.T) {
			f, err := gfs.Open(tc.path)
			if tc.wantErr && err == nil {
				t.Errorf("expected error, got file")
				if f != nil {
					f.Close()
				}
			} else if !tc.wantErr && err != nil {
				t.Errorf("unexpected error: %v", err)
			} else if !tc.wantErr && err == nil {
				info, _ := f.Stat()
				if info.IsDir() {
					_, derr := fs.ReadDir(gfs, tc.path)
					if derr != nil && !tc.wantErr {
						t.Errorf("unexpected error: %v", derr)
					}
				}
				f.Close()
			}
		})
	}
}

func TestGlobFSReadFile(t *testing.T) {
	memfs := setupFS()
	gfs := NewGlobFS(memfs, "*.go", "*.md", "assets/*", ".gitignore")

	tests := []struct {
		name    string
		want    []byte
		wantErr bool
	}{
		{name: "main.go", want: []byte("package main")},
		{name: "main_test.go", want: []byte("package main_test")},
		{name: "README.md", want: []byte("# readme")},
		{name: "assets/img.png", want: []byte("PNG")},
		{name: "assets/style.css", want: []byte("CSS")},
		{name: ".gitignore", want: []byte("*.log")},
		{name: "LICENSE", wantErr: true},           // not allowed by filter
		{name: "docs/guide.md", wantErr: true},     // not allowed by filter
		{name: "docs/hidden/.keep", wantErr: true}, // not allowed by filter
		{name: "doesnotexist.txt", wantErr: true},  // does not exist
	}

	for _, tc := range tests {
		tc := tc
		t.Run(tc.name, func(t *testing.T) {
			got, err := fs.ReadFile(gfs, tc.name)
			if tc.wantErr {
				if err == nil {
					t.Errorf("expected error, got nil (got=%q)", got)
				}
			} else {
				if err != nil {
					t.Errorf("unexpected error: %v", err)
				}
				if string(got) != string(tc.want) {
					t.Errorf("got %q; want %q", got, tc.want)
				}
			}
		})
	}
}

func TestGlobFSRelativePaths(t *testing.T) {
	memfs := setupFS()
	gfs := NewGlobFS(memfs, "docs/*.md")
	entries, err := fs.ReadDir(gfs, "docs")
	if err != nil {
		t.Fatal(err)
	}
	got := basenames(entries)
	want := []string{"guide.md"}
	if !reflect.DeepEqual(got, want) {
		t.Errorf("docs/*.md: got %v, want %v", got, want)
	}
}

func TestGlobFSNoMatchesOpen(t *testing.T) {
	gfs := NewGlobFS(setupFS(), "*.xyz")
	_, err := gfs.Open("main.go")
	if err == nil {
		t.Fatal("expected error when opening file with no matches")
	}
}

func TestGlobFSNoMatchesStat(t *testing.T) {
	gfs := NewGlobFS(setupFS(), "*.xyz")
	_, err := fs.Stat(gfs, "main.go")
	if err == nil {
		t.Fatal("expected error with no matches: stat")
	}
}

func TestGlobFSNoMatchesReadDir(t *testing.T) {
	gfs := NewGlobFS(setupFS(), "*.xyz")
	_, err := fs.ReadDir(gfs, "main.go")
	if err == nil {
		t.Fatal("expected error with no matches: readdir")
	}
}

func TestGlobFSNoMatchesReadFile(t *testing.T) {
	gfs := NewGlobFS(setupFS(), "*.xyz")
	_, err := fs.ReadFile(gfs, "main.go")
	if err == nil {
		t.Fatal("expected error with no matches: readfile")
	}
}

func TestGlobFS_IntegrationWithStdlib(t *testing.T) {
	memfs := setupFS()
	gfs := NewGlobFS(memfs, "*.go", "docs/guide.md")
	// Use fs.WalkDir with our filtered FS
	var walked []string
	err := fs.WalkDir(gfs, ".", func(path string, d fs.DirEntry, err error) error {
		if err != nil {
			return err
		}
		walked = append(walked, path)
		return nil
	})
	if err != nil {
		t.Fatal(err)
	}
	// Only files and dirs matching or containing matches should appear
	for _, p := range walked {
		if p == "." || p == "main.go" || p == "main_test.go" || p == "docs" || p == "docs/guide.md" {
			continue
		}
		t.Errorf("WalkDir: unexpected path %q", p)
	}
}