package depot

import (
	"bytes"
	"context"
	"crypto/sha256"
	"fmt"
	"os"
	"path/filepath"
	"testing"
)

func TestLocalRoundTrip(t *testing.T) {
	tmpDir := t.TempDir()
	backend := &LocalBackend{Root: tmpDir}

	// Generate test data
	testData := []byte("hello world")
	testSHA := fmt.Sprintf("%x", sha256.Sum256(testData))

	// Create source file
	srcFile := filepath.Join(tmpDir, "source.txt")
	if err := os.WriteFile(srcFile, testData, 0644); err != nil {
		t.Fatalf("failed to create source file: %v", err)
	}

	// Put
	ctx := context.Background()
	if err := backend.Put(ctx, testSHA, srcFile); err != nil {
		t.Fatalf("Put failed: %v", err)
	}

	// Probe should be Present
	state, transient, err := backend.Probe(ctx, testSHA)
	if err != nil {
		t.Fatalf("Probe failed: %v", err)
	}
	if state != Present {
		t.Fatalf("expected Present, got %v", state)
	}
	if transient {
		t.Fatalf("local backend should never be transient")
	}

	// Get
	destFile := filepath.Join(tmpDir, "dest.txt")
	if err := backend.Get(ctx, testSHA, destFile); err != nil {
		t.Fatalf("Get failed: %v", err)
	}

	// Verify bytes match
	gotData, err := os.ReadFile(destFile)
	if err != nil {
		t.Fatalf("failed to read dest file: %v", err)
	}
	if !bytes.Equal(gotData, testData) {
		t.Fatalf("data mismatch: want %s, got %s", testData, gotData)
	}
}

func TestLocalProbeAbsent(t *testing.T) {
	tmpDir := t.TempDir()
	backend := &LocalBackend{Root: tmpDir}

	ctx := context.Background()
	state, transient, err := backend.Probe(ctx, "0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d")
	if err != nil {
		t.Fatalf("Probe should not error on missing blob: %v", err)
	}
	if state != Absent {
		t.Fatalf("expected Absent, got %v", state)
	}
	if transient {
		t.Fatalf("local backend should never be transient")
	}
}

func TestLocalGetHashMismatch(t *testing.T) {
	tmpDir := t.TempDir()
	backend := &LocalBackend{Root: tmpDir}

	// Create a corrupt blob at the expected path
	sha := "0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d0b1d"
	blobKey := BlobKey(sha)
	blobPath := filepath.Join(tmpDir, blobKey)

	if err := os.MkdirAll(filepath.Dir(blobPath), 0755); err != nil {
		t.Fatalf("failed to create blob dir: %v", err)
	}
	if err := os.WriteFile(blobPath, []byte("wrong data"), 0644); err != nil {
		t.Fatalf("failed to create blob file: %v", err)
	}

	// Get should error
	ctx := context.Background()
	destFile := filepath.Join(tmpDir, "dest.txt")
	err := backend.Get(ctx, sha, destFile)
	if err == nil {
		t.Fatalf("Get should error on hash mismatch")
	}

	// Destination file should not exist
	_, err = os.Stat(destFile)
	if !os.IsNotExist(err) {
		t.Fatalf("dest file should not exist after Get error: %v", err)
	}
}

func TestLocalPutIdempotent(t *testing.T) {
	tmpDir := t.TempDir()
	backend := &LocalBackend{Root: tmpDir}

	testData := []byte("hello world")
	testSHA := fmt.Sprintf("%x", sha256.Sum256(testData))

	srcFile := filepath.Join(tmpDir, "source.txt")
	if err := os.WriteFile(srcFile, testData, 0644); err != nil {
		t.Fatalf("failed to create source file: %v", err)
	}

	ctx := context.Background()

	// Put twice
	if err := backend.Put(ctx, testSHA, srcFile); err != nil {
		t.Fatalf("first Put failed: %v", err)
	}
	if err := backend.Put(ctx, testSHA, srcFile); err != nil {
		t.Fatalf("second Put failed: %v", err)
	}

	// Verify blob exists
	state, _, err := backend.Probe(ctx, testSHA)
	if err != nil {
		t.Fatalf("Probe failed: %v", err)
	}
	if state != Present {
		t.Fatalf("expected Present after Put, got %v", state)
	}
}