package persistence

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

func writeTestFile(t *testing.T, path, content string) {
	t.Helper()
	if err := os.MkdirAll(filepath.Dir(path), 0755); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(path, []byte(content), 0644); err != nil {
		t.Fatal(err)
	}
}

func readTestFile(t *testing.T, path string) string {
	t.Helper()
	data, err := os.ReadFile(path)
	if err != nil {
		t.Fatal(err)
	}
	return string(data)
}

func TestTxnCommitAppliesAllOps(t *testing.T) {
	dir := t.TempDir()
	journalDir := filepath.Join(dir, ".journal")
	writeTestFile(t, filepath.Join(dir, "a.yaml"), "old-a")
	writeTestFile(t, filepath.Join(dir, "b.yaml"), "old-b")
	writeTestFile(t, filepath.Join(dir, "c.yaml"), "old-c")

	txn := NewTransaction(journalDir)
	if err := txn.Replace(filepath.Join(dir, "a.yaml"), []byte("new-a"), 0644); err != nil {
		t.Fatal(err)
	}
	if err := txn.Delete(filepath.Join(dir, "b.yaml")); err != nil {
		t.Fatal(err)
	}
	if err := txn.Move(filepath.Join(dir, "c.yaml"), filepath.Join(dir, "d.yaml")); err != nil {
		t.Fatal(err)
	}
	if err := txn.Replace(filepath.Join(dir, "created.yaml"), []byte("created"), 0600); err != nil {
		t.Fatal(err)
	}

	if err := txn.Commit(); err != nil {
		t.Fatalf("commit: %v", err)
	}
	if got := readTestFile(t, filepath.Join(dir, "a.yaml")); got != "new-a" {
		t.Fatalf("replace failed: %q", got)
	}
	if _, err := os.Stat(filepath.Join(dir, "b.yaml")); !os.IsNotExist(err) {
		t.Fatalf("delete failed: %v", err)
	}
	if _, err := os.Stat(filepath.Join(dir, "c.yaml")); !os.IsNotExist(err) {
		t.Fatalf("move left source behind: %v", err)
	}
	if got := readTestFile(t, filepath.Join(dir, "d.yaml")); got != "old-c" {
		t.Fatalf("move lost content: %q", got)
	}
	if got := readTestFile(t, filepath.Join(dir, "created.yaml")); got != "created" {
		t.Fatalf("create failed: %q", got)
	}
	if entries, _ := ListJournalFiles(journalDir); len(entries) != 0 {
		t.Fatalf("journal not cleaned: %v", entries)
	}
}

func TestTxnRollbackOnFailure(t *testing.T) {
	dir := t.TempDir()
	journalDir := filepath.Join(dir, ".journal")
	writeTestFile(t, filepath.Join(dir, "a.yaml"), "old-a")
	// A file inside a read-only subdirectory makes the delete fail.
	sub := filepath.Join(dir, "sub")
	writeTestFile(t, filepath.Join(sub, "gone.yaml"), "old-gone")
	if err := os.Chmod(sub, 0500); err != nil {
		t.Fatal(err)
	}
	t.Cleanup(func() { os.Chmod(sub, 0700) })

	txn := NewTransaction(journalDir)
	if err := txn.Replace(filepath.Join(dir, "a.yaml"), []byte("new-a"), 0644); err != nil {
		t.Fatal(err)
	}
	if err := txn.Delete(filepath.Join(sub, "gone.yaml")); err != nil {
		t.Fatal(err)
	}
	if err := txn.Commit(); err == nil {
		t.Fatal("expected commit to fail")
	}

	if got := readTestFile(t, filepath.Join(dir, "a.yaml")); got != "old-a" {
		t.Fatalf("rollback did not restore a.yaml: %q", got)
	}
	if got := readTestFile(t, filepath.Join(sub, "gone.yaml")); got != "old-gone" {
		t.Fatalf("rollback did not restore deleted file: %q", got)
	}
	if entries, _ := ListJournalFiles(journalDir); len(entries) != 0 {
		t.Fatalf("journal not cleaned after rollback: %v", entries)
	}
}

func TestRecoverRollsBackLeftoverJournal(t *testing.T) {
	// Simulate a crash: journal exists (it says a.yaml becomes new-a and
	// c.yaml is deleted) but the operations never ran.
	dir := t.TempDir()
	journalDir := filepath.Join(dir, ".journal")
	writeTestFile(t, filepath.Join(dir, "a.yaml"), "old-a")
	writeTestFile(t, filepath.Join(dir, "c.yaml"), "old-c")

	txn := NewTransaction(journalDir)
	if err := txn.Replace(filepath.Join(dir, "a.yaml"), []byte("new-a"), 0644); err != nil {
		t.Fatal(err)
	}
	if err := txn.Delete(filepath.Join(dir, "c.yaml")); err != nil {
		t.Fatal(err)
	}
	journal, err := txn.MarshalJournal()
	if err != nil {
		t.Fatal(err)
	}
	if err := os.MkdirAll(journalDir, 0700); err != nil {
		t.Fatal(err)
	}
	if err := WriteFile(filepath.Join(journalDir, "txn-crash.json"), journal, 0600); err != nil {
		t.Fatal(err)
	}

	if err := Recover(journalDir); err != nil {
		t.Fatalf("recover: %v", err)
	}
	if got := readTestFile(t, filepath.Join(dir, "a.yaml")); got != "old-a" {
		t.Fatalf("recovery did not roll back a.yaml: %q", got)
	}
	if got := readTestFile(t, filepath.Join(dir, "c.yaml")); got != "old-c" {
		t.Fatalf("recovery resurrected a delete: %q", got)
	}
	if entries, _ := ListJournalFiles(journalDir); len(entries) != 0 {
		t.Fatalf("recovered journal not removed: %v", entries)
	}
}

func TestRecoverDropsCorruptJournal(t *testing.T) {
	dir := t.TempDir()
	journalDir := filepath.Join(dir, ".journal")
	if err := os.MkdirAll(journalDir, 0700); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(filepath.Join(journalDir, "txn-bad.json"), []byte("{not json"), 0600); err != nil {
		t.Fatal(err)
	}
	if err := Recover(journalDir); err != nil {
		t.Fatalf("recover corrupt: %v", err)
	}
	if entries, _ := ListJournalFiles(journalDir); len(entries) != 0 {
		t.Fatalf("corrupt journal not removed: %v", entries)
	}
}

func TestTxnMoveOverwritesDestination(t *testing.T) {
	dir := t.TempDir()
	journalDir := filepath.Join(dir, ".journal")
	writeTestFile(t, filepath.Join(dir, "src.yaml"), "src-content")
	writeTestFile(t, filepath.Join(dir, "dst.yaml"), "dst-content")

	txn := NewTransaction(journalDir)
	if err := txn.Move(filepath.Join(dir, "src.yaml"), filepath.Join(dir, "dst.yaml")); err != nil {
		t.Fatal(err)
	}
	if err := txn.Commit(); err != nil {
		t.Fatalf("commit: %v", err)
	}
	if got := readTestFile(t, filepath.Join(dir, "dst.yaml")); got != "src-content" {
		t.Fatalf("move did not overwrite destination: %q", got)
	}
	if _, err := os.Stat(filepath.Join(dir, "src.yaml")); !os.IsNotExist(err) {
		t.Fatalf("source not removed: %v", err)
	}
	if !strings.HasSuffix(readTestFile(t, filepath.Join(dir, "dst.yaml")), "content") {
		t.Fatal("unreachable")
	}
}