package files

import (
	"context"
	"errors"
	"os"
	"path/filepath"
	"strings"
	"syscall"
	"testing"
	"time"
)

func TestInside(t *testing.T) {
	for _, c := range []struct {
		from, to string
		want     bool
	}{
		{"/a/b", "/a/b", true}, {"/a/b", "/a/b/c", true}, {"/a/b", "/a/bc", false}, {"/a/b", "/a", false}, {"/", "/x", true},
	} {
		if got := Inside(c.from, c.to); got != c.want {
			t.Errorf("Inside(%q, %q) = %v, want %v", c.from, c.to, got, c.want)
		}
	}
}

func TestIsCrossDevice(t *testing.T) {
	if !IsCrossDevice(&os.LinkError{Op: "rename", Old: "/a", New: "/b", Err: syscall.EXDEV}) {
		t.Fatal("the kernel's EXDEV")
	}
	if !IsCrossDevice(errors.New("rename /a /b: invalid cross-device link")) {
		t.Fatal("the helper's words for it")
	}
	if IsCrossDevice(errors.New("permission denied")) || IsCrossDevice(nil) {
		t.Fatal("anything else is not")
	}
}

// The copy path, exercised directly: a tree with nested folders, a symlink, an odd mode
// and old mtimes lands whole under the new name, and the original is gone only then.
func TestMoveByCopy(t *testing.T) {
	root := t.TempDir()
	src := filepath.Join(root, "src", "album")
	if err := os.MkdirAll(filepath.Join(src, "sub", "deep"), 0o755); err != nil {
		t.Fatal(err)
	}
	old := time.Date(2020, 1, 2, 3, 4, 5, 0, time.UTC)
	write := func(p, s string, mode os.FileMode) {
		if err := os.WriteFile(p, []byte(s), mode); err != nil {
			t.Fatal(err)
		}
		_ = os.Chmod(p, mode)
		_ = os.Chtimes(p, old, old)
	}
	write(filepath.Join(src, "a.txt"), "hello", 0o644)
	write(filepath.Join(src, "sub", "deep", "b.bin"), strings.Repeat("x", 100000), 0o600)
	write(filepath.Join(src, "run.sh"), "#!/bin/sh\n", 0o755)
	if err := os.Symlink("a.txt", filepath.Join(src, "link")); err != nil {
		t.Fatal(err)
	}
	_ = os.Chtimes(filepath.Join(src, "sub"), old, old)

	dst := filepath.Join(root, "dst", "moved")
	if err := os.MkdirAll(filepath.Dir(dst), 0o755); err != nil {
		t.Fatal(err)
	}
	var out strings.Builder
	if err := moveByCopy(context.Background(), src, dst, &out); err != nil {
		t.Fatal(err)
	}
	if _, err := os.Lstat(src); !os.IsNotExist(err) {
		t.Fatal("the original is still there")
	}
	if b, _ := os.ReadFile(filepath.Join(dst, "a.txt")); string(b) != "hello" {
		t.Fatal("a.txt")
	}
	if st, err := os.Stat(filepath.Join(dst, "sub", "deep", "b.bin")); err != nil || st.Size() != 100000 || st.Mode().Perm() != 0o600 || !st.ModTime().Equal(old) {
		t.Fatalf("b.bin: %v %v", st, err)
	}
	if st, _ := os.Stat(filepath.Join(dst, "run.sh")); st.Mode().Perm() != 0o755 {
		t.Fatal("mode lost")
	}
	if target, err := os.Readlink(filepath.Join(dst, "link")); err != nil || target != "a.txt" {
		t.Fatal("symlink not copied as a symlink")
	}
	if st, _ := os.Stat(filepath.Join(dst, "sub")); !st.ModTime().Equal(old) {
		t.Fatal("folder mtime lost")
	}
	if left, _ := filepath.Glob(filepath.Join(root, "dst", ".*hamlab-moving*")); len(left) != 0 {
		t.Fatal("temporary copy left behind")
	}
	if !strings.Contains(out.String(), "moved ") || !strings.Contains(out.String(), "4 files") {
		t.Fatalf("progress said: %q", out.String())
	}
}

// A failure part-way leaves the original as it was and no partial copy.
func TestMoveByCopyFailsClean(t *testing.T) {
	root := t.TempDir()
	src := filepath.Join(root, "src")
	if err := os.MkdirAll(src, 0o755); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(filepath.Join(src, "a"), []byte("a"), 0o644); err != nil {
		t.Fatal(err)
	}
	if err := syscall.Mkfifo(filepath.Join(src, "pipe"), 0o644); err != nil {
		t.Skip("no fifos here")
	}
	dst := filepath.Join(root, "dst")
	err := moveByCopy(context.Background(), src, dst, &strings.Builder{})
	if err == nil || !strings.Contains(err.Error(), "pipe") {
		t.Fatalf("expected the pipe to be refused, got %v", err)
	}
	if _, err := os.Stat(filepath.Join(src, "a")); err != nil {
		t.Fatal("the original was touched")
	}
	if _, err := os.Lstat(dst); !os.IsNotExist(err) {
		t.Fatal("a partial copy was left")
	}
	if left, _ := filepath.Glob(filepath.Join(root, ".*hamlab-moving*")); len(left) != 0 {
		t.Fatal("temporary copy left behind")
	}
	// a cancel is the same story
	if err := os.Remove(filepath.Join(src, "pipe")); err != nil {
		t.Fatal(err)
	}
	ctx, cancel := context.WithCancel(context.Background())
	cancel()
	if err := moveByCopy(ctx, src, dst, &strings.Builder{}); err == nil {
		t.Fatal("a cancelled move must fail")
	}
	if _, err := os.Stat(filepath.Join(src, "a")); err != nil {
		t.Fatal("the original was touched by a cancel")
	}
}

// Move on one filesystem is a rename: nothing is copied, and the guards hold.
func TestMoveSameFilesystem(t *testing.T) {
	root := t.TempDir()
	src := filepath.Join(root, "f")
	if err := os.WriteFile(src, []byte("x"), 0o644); err != nil {
		t.Fatal(err)
	}
	var l Local
	var out strings.Builder
	if err := l.Move(context.Background(), src, filepath.Join(root, "g"), &out); err != nil {
		t.Fatal(err)
	}
	if out.Len() != 0 {
		t.Fatal("a rename has nothing to say")
	}
	if _, err := os.Stat(filepath.Join(root, "g")); err != nil {
		t.Fatal("not renamed")
	}
	if err := l.Move(context.Background(), root, filepath.Join(root, "inside"), &out); err == nil {
		t.Fatal("into itself")
	}
	if err := l.Move(context.Background(), filepath.Join(root, "g"), filepath.Join(root, "g"), &out); err == nil {
		t.Fatal("onto itself")
	}
	if err := os.WriteFile(filepath.Join(root, "h"), nil, 0o644); err != nil {
		t.Fatal(err)
	}
	if err := l.Move(context.Background(), filepath.Join(root, "g"), filepath.Join(root, "h"), &out); err == nil || !strings.Contains(err.Error(), "exists") {
		t.Fatalf("onto an existing file: %v", err)
	}
}