package testhelpers

import (
	"fmt"
	"os"
	"strings"
	"testing"
	"time"

	"gorm.io/driver/postgres"
	"gorm.io/driver/sqlite"
	"gorm.io/gorm"
	"gorm.io/gorm/logger"

	"github.com/gochat/gochat/internal/model"
	"github.com/gochat/gochat/internal/model/channel"
)

// DSN returns a PostgreSQL connection string for testing.
// Priority: GOCHAT_TEST_DB_URL env > default localhost PG.
func testDSN() string {
	dsn := os.Getenv("GOCHAT_TEST_DB_URL")
	if dsn != "" {
		return dsn
	}
	return "host=localhost port=5432 user=postgres password=postgres dbname=gochat_test sslmode=disable"
}

// UsePostgres returns true when a PostgreSQL test database is reachable.
// Tests that require PG-specific features (ILIKE, NULLS LAST, etc.) should
// check this flag and skip gracefully when PG is unavailable.
func UsePostgres() bool {
	return os.Getenv("GOCHAT_TEST_DB") != "sqlite"
}

// SetupTestDB creates an isolated test database.
// When UsePostgres() is true, connects to the PG test instance (docker-compose.test.yml)
// and creates a per-test isolated schema. Otherwise falls back to SQLite in-memory.
//
// The returned DB has all GoChat models auto-migrated.
// Call t.Cleanup(func(){ ... }) for teardown if needed.
func SetupTestDB(t *testing.T) *gorm.DB {
	t.Helper()

	if UsePostgres() {
		db := setupPostgresDB(t)
		autoMigrateAll(t, db)
		return db
	}

	return setupSQLiteDB(t)
}

// SetupIsolatedDB creates a truly isolated database per test.
// For PG: creates a separate schema with random suffix.
// For SQLite: creates a fresh in-memory database.
func SetupIsolatedDB(t *testing.T) *gorm.DB {
	t.Helper()

	if UsePostgres() {
		db := setupPostgresIsolatedDB(t)
		autoMigrateAll(t, db)
		return db
	}

	return setupSQLiteDB(t)
}

func setupPostgresDB(t *testing.T) *gorm.DB {
	t.Helper()

	dsn := testDSN()
	db, err := gorm.Open(postgres.Open(dsn), &gorm.Config{
		Logger:                 logger.Default.LogMode(logger.Silent),
		PrepareStmt:            true,
		DisableForeignKeyConstraintWhenMigrating: true,
	})
	if err != nil {
		t.Fatalf("failed to connect to PostgreSQL test db: %v\nSet GOCHAT_TEST_DB=sqlite to fall back to SQLite", err)
	}

	sqlDB, err := db.DB()
	if err != nil {
		t.Fatalf("failed to get underlying sql.DB: %v", err)
	}
	sqlDB.SetMaxOpenConns(10)
	sqlDB.SetMaxIdleConns(5)
	sqlDB.SetConnMaxLifetime(5 * time.Minute)

	t.Cleanup(func() {
		// Clean all test data — drop and recreate tables
		for _, m := range allModels() {
			db.Exec(fmt.Sprintf("TRUNCATE TABLE %s CASCADE", tableName(m)))
		}
		sqlDB.Close()
	})

	return db
}

func setupPostgresIsolatedDB(t *testing.T) *gorm.DB {
	t.Helper()

	schemaName := fmt.Sprintf("test_%s_%d", t.Name(), time.Now().UnixNano())
	// PostgreSQL schema names can't contain / from subtests, sanitize
	schemaName = sanitizeSchemaName(schemaName)

	dsn := testDSN()
	db, err := gorm.Open(postgres.Open(dsn), &gorm.Config{
		Logger:                 logger.Default.LogMode(logger.Silent),
		PrepareStmt:            true,
		DisableForeignKeyConstraintWhenMigrating: true,
	})
	if err != nil {
		t.Fatalf("failed to connect to PostgreSQL test db: %v", err)
	}

	// Create isolated schema
	db.Exec(fmt.Sprintf("CREATE SCHEMA %s", schemaName))
	db.Exec(fmt.Sprintf("SET search_path TO %s, public", schemaName))

	t.Cleanup(func() {
		db.Exec(fmt.Sprintf("DROP SCHEMA %s CASCADE", schemaName))
		sqlDB, _ := db.DB()
		sqlDB.Close()
	})

	return db
}

func setupSQLiteDB(t *testing.T) *gorm.DB {
	t.Helper()

	db, err := gorm.Open(sqlite.Open("file::memory:"), &gorm.Config{
		Logger: logger.Default.LogMode(logger.Silent),
	})
	if err != nil {
		t.Fatalf("failed to open SQLite in-memory db: %v", err)
	}

	autoMigrateAll(t, db)

	t.Cleanup(func() {
		sqlDB, _ := db.DB()
		sqlDB.Close()
	})

	return db
}

func autoMigrateAll(t *testing.T, db *gorm.DB) {
	t.Helper()

	models := allModels()
	for _, m := range models {
		if err := db.AutoMigrate(m); err != nil {
			t.Fatalf("failed to auto-migrate %T: %v", m, err)
		}
	}
}

func allModels() []interface{} {
	return []interface{}{
		// Core models
		&model.Account{},
		&model.AccountUser{},
		&model.User{},
		&model.Contact{},
		&model.ContactInbox{},
		&model.Conversation{},
		&model.Inbox{},
		&model.InboxMember{},
		&model.Message{},
		&model.Attachment{},
		&model.Notification{},
		&model.NotificationPreference{},
		&model.CustomRole{},
		&model.PlatformApp{},
		&model.DashboardApp{},
		&model.ReportingEvent{},
		&model.ReportingEventsRollup{},
		// Captain (AI assistant) models
		&model.CaptainAssistant{},
		&model.CaptainAssistantResponse{},
		&model.CaptainCustomTool{},
		&model.CaptainDocument{},
		&model.CaptainInbox{},
		&model.CaptainScenario{},
		// Copilot models
		&model.CopilotMessage{},
		&model.CopilotThread{},
		// Channel models
		&channel.ChannelBase{},
		&channel.ChannelFacebook{},
		&channel.ChannelTelegram{},
		&channel.ChannelWebWidget{},
		&channel.ChannelWhatsApp{},
	}
}

func tableName(m interface{}) string {
	// All GoChat models implement a TableName() method.
	// Use a type assertion via a local interface to call it directly —
	// avoids needing a live gorm.DB instance (which Statement.Parse requires).
	type tabler interface {
		TableName() string
	}
	if t, ok := m.(tabler); ok {
		return t.TableName()
	}
	// Fallback: pluralize the struct type name using GORM convention.
	// This should not normally be needed since all our models have TableName().
	name := fmt.Sprintf("%T", m)
	// Strip pointer prefix and package path (e.g. "*model.Account" → "Account")
	if name[0] == '*' {
		name = name[1:]
	}
	if idx := strings.LastIndex(name, "."); idx >= 0 {
		name = name[idx+1:]
	}
	// Simple snake_case + pluralize approximation
	return toSnakeCase(name) + "s"
}

// toSnakeCase converts CamelCase to snake_case.
func toSnakeCase(s string) string {
	var result strings.Builder
	for i, c := range s {
		if c >= 'A' && c <= 'Z' {
			if i > 0 {
				result.WriteRune('_')
			}
			result.WriteRune(c + ('a' - 'A'))
		} else {
			result.WriteRune(c)
		}
	}
	return result.String()
}

func sanitizeSchemaName(name string) string {
	// Replace non-alphanumeric chars with underscore
	result := make([]byte, 0, len(name))
	for _, c := range name {
		if (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9') || c == '_' {
			result = append(result, byte(c))
		} else {
			result = append(result, '_')
		}
	}
	// Ensure starts with letter
	if len(result) > 0 && result[0] >= '0' && result[0] <= '9' {
		result = append([]byte("t"), result...)
	}
	// Truncate to PostgreSQL max identifier length (63 chars)
	if len(result) > 63 {
		result = result[:63]
	}
	return string(result)
}