package main

import (
	"fmt"
	"os"
	"path/filepath"
	"testing"

	"github.com/gochat/gochat/internal/database"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

// setupTestMigrations creates a temporary directory with test migration files
// that are compatible with SQLite (no PostgreSQL-specific features).
func setupTestMigrations(t *testing.T) string {
	t.Helper()
	dir := t.TempDir()

	// Migration 1: Create a simple users table (SQLite-compatible)
	up1 := `
CREATE TABLE IF NOT EXISTS test_users (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    name TEXT NOT NULL,
    email TEXT NOT NULL UNIQUE,
    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
    updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
);
`
	down1 := `DROP TABLE IF EXISTS test_users;`
	require.NoError(t, os.WriteFile(filepath.Join(dir, "000001_create_test_users.up.sql"), []byte(up1), 0644))
	require.NoError(t, os.WriteFile(filepath.Join(dir, "000001_create_test_users.down.sql"), []byte(down1), 0644))

	// Migration 2: Add a phone column
	up2 := `
ALTER TABLE test_users ADD COLUMN phone TEXT;
`
	down2 := `
-- SQLite doesn't support DROP COLUMN before 3.35.0, so we recreate the table
CREATE TABLE test_users_backup AS SELECT id, name, email, created_at, updated_at FROM test_users;
DROP TABLE test_users;
CREATE TABLE test_users (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    name TEXT NOT NULL,
    email TEXT NOT NULL UNIQUE,
    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
    updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
);
INSERT INTO test_users SELECT id, name, email, created_at, updated_at FROM test_users_backup;
DROP TABLE test_users_backup;
`
	require.NoError(t, os.WriteFile(filepath.Join(dir, "000002_add_test_user_phone.up.sql"), []byte(up2), 0644))
	require.NoError(t, os.WriteFile(filepath.Join(dir, "000002_add_test_user_phone.down.sql"), []byte(down2), 0644))

	// Migration 3: Create a posts table
	up3 := `
CREATE TABLE IF NOT EXISTS test_posts (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    user_id INTEGER NOT NULL REFERENCES test_users(id),
    title TEXT NOT NULL,
    content TEXT,
    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
    updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
);
`
	down3 := `DROP TABLE IF EXISTS test_posts;`
	require.NoError(t, os.WriteFile(filepath.Join(dir, "000003_create_test_posts.up.sql"), []byte(up3), 0644))
	require.NoError(t, os.WriteFile(filepath.Join(dir, "000003_create_test_posts.down.sql"), []byte(down3), 0644))

	return dir
}

// sqliteDBURL creates a SQLite database URL for golang-migrate.
func sqliteDBURL(t *testing.T) string {
	t.Helper()
	dbPath := filepath.Join(t.TempDir(), "test.db")
	return fmt.Sprintf("sqlite3://%s", dbPath)
}

func TestRunMigrationsUp(t *testing.T) {
	migrationsDir := setupTestMigrations(t)
	dbURL := sqliteDBURL(t)

	err := database.RunMigrations(dbURL, migrationsDir)
	assert.NoError(t, err, "RunMigrations should apply all pending migrations")

	// Verify current version is 3
	version, dirty, err := database.CurrentVersion(dbURL, migrationsDir)
	assert.NoError(t, err)
	assert.Equal(t, uint(3), version)
	assert.False(t, dirty)
}

func TestRunMigrationsNoChange(t *testing.T) {
	migrationsDir := setupTestMigrations(t)
	dbURL := sqliteDBURL(t)

	// First run: apply all migrations
	err := database.RunMigrations(dbURL, migrationsDir)
	require.NoError(t, err)

	// Second run: should return nil (ErrNoChange is handled)
	err = database.RunMigrations(dbURL, migrationsDir)
	assert.NoError(t, err, "Running migrations with no pending changes should succeed")
}

func TestMigrateStepsUp(t *testing.T) {
	migrationsDir := setupTestMigrations(t)
	dbURL := sqliteDBURL(t)

	// Apply 1 step at a time
	err := database.MigrateSteps(dbURL, migrationsDir, 1)
	require.NoError(t, err)

	version, dirty, err := database.CurrentVersion(dbURL, migrationsDir)
	require.NoError(t, err)
	assert.Equal(t, uint(1), version)
	assert.False(t, dirty)

	// Apply 2 more steps
	err = database.MigrateSteps(dbURL, migrationsDir, 2)
	require.NoError(t, err)

	version, dirty, err = database.CurrentVersion(dbURL, migrationsDir)
	require.NoError(t, err)
	assert.Equal(t, uint(3), version)
	assert.False(t, dirty)
}

func TestMigrateStepsDown(t *testing.T) {
	migrationsDir := setupTestMigrations(t)
	dbURL := sqliteDBURL(t)

	// First, apply all migrations
	err := database.RunMigrations(dbURL, migrationsDir)
	require.NoError(t, err)

	// Rollback 1 step
	err = database.MigrateSteps(dbURL, migrationsDir, -1)
	require.NoError(t, err)

	version, _, err := database.CurrentVersion(dbURL, migrationsDir)
	require.NoError(t, err)
	assert.Equal(t, uint(2), version)

	// Rollback 2 more steps
	err = database.MigrateSteps(dbURL, migrationsDir, -2)
	require.NoError(t, err)

	version, _, err = database.CurrentVersion(dbURL, migrationsDir)
	require.NoError(t, err)
	assert.Equal(t, uint(0), version)
}

func TestRollbackMigrations(t *testing.T) {
	migrationsDir := setupTestMigrations(t)
	dbURL := sqliteDBURL(t)

	// Apply all migrations first
	err := database.RunMigrations(dbURL, migrationsDir)
	require.NoError(t, err)

	// Rollback all
	err = database.RollbackMigrations(dbURL, migrationsDir)
	assert.NoError(t, err, "RollbackMigrations should succeed")

	version, _, err := database.CurrentVersion(dbURL, migrationsDir)
	require.NoError(t, err)
	assert.Equal(t, uint(0), version, "All migrations should be rolled back")
}

func TestRollbackNoChange(t *testing.T) {
	migrationsDir := setupTestMigrations(t)
	dbURL := sqliteDBURL(t)

	// Try to rollback when no migrations have been applied
	err := database.RollbackMigrations(dbURL, migrationsDir)
	assert.NoError(t, err, "Rollback with no applied migrations should succeed (ErrNoChange)")
}

func TestForceVersion(t *testing.T) {
	migrationsDir := setupTestMigrations(t)
	dbURL := sqliteDBURL(t)

	// Apply all migrations first
	err := database.RunMigrations(dbURL, migrationsDir)
	require.NoError(t, err)

	// Force version to 1
	err = database.ForceVersion(dbURL, migrationsDir, 1)
	require.NoError(t, err)

	version, dirty, err := database.CurrentVersion(dbURL, migrationsDir)
	require.NoError(t, err)
	assert.Equal(t, uint(1), version)
	// After Force, dirty state should be cleared
	assert.False(t, dirty)
}

func TestCurrentVersion(t *testing.T) {
	migrationsDir := setupTestMigrations(t)
	dbURL := sqliteDBURL(t)

	// Before any migrations, version should be 0 (with ErrNoChange handled internally)
	version, dirty, err := database.CurrentVersion(dbURL, migrationsDir)
	// When no migrations have been applied, Version returns an error
	// This is expected — golang-migrate returns ErrNoChange for version 0
	if err != nil {
		t.Logf("Expected: version 0 with no migrations applied may return error: %v", err)
	}

	// Apply migrations
	err = database.RunMigrations(dbURL, migrationsDir)
	require.NoError(t, err)

	version, dirty, err = database.CurrentVersion(dbURL, migrationsDir)
	require.NoError(t, err)
	assert.Equal(t, uint(3), version)
	assert.False(t, dirty)
}