// Clavitor Generic Dual-Write Abstraction Layer
// JSON in → writes to our DB + Paddle API automatically

package main

import (
	"bytes"
	"database/sql"
	"encoding/json"
	"fmt"
	"io"
	"net"
	"net/http"
	"strings"
	"time"
)

// isProductionServer checks if we're running on the production clavitor.ai server
func isProductionServer() bool {
	prodIPs, err := net.LookupIP("clavitor.ai")
	if err != nil || len(prodIPs) == 0 {
		return false
	}

	addrs, err := net.InterfaceAddrs()
	if err != nil {
		return false
	}

	for _, addr := range addrs {
		if ipnet, ok := addr.(*net.IPNet); ok && !ipnet.IP.IsLoopback() {
			if ipnet.IP.To4() != nil {
				for _, prodIP := range prodIPs {
					if ipnet.IP.Equal(prodIP) {
						return true
					}
				}
			}
		}
	}
	return false
}

// EntityMap defines how each entity maps between our DB and Paddle
type EntityMap struct {
	PaddleEndpoint string            // e.g., "/customers"
	IDPrefix       string            // e.g., "ctm"
	DBTable        string            // e.g., "customers"
	FieldMap       map[string]string // our_field → paddle_field (if different)
	RequiredFields []string          // Must be present in input
}

// Registry of all known entities
var EntityRegistry = map[string]EntityMap{
	"customers": {
		PaddleEndpoint: "/customers",
		IDPrefix:       "ctm",
		DBTable:        "customers",
		FieldMap: map[string]string{
			"id":         "",   // we generate this
			"paddle_id":  "id", // store Paddle's ID separately
			"created_at": "created_at",
			"updated_at": "updated_at",
		},
		RequiredFields: []string{"email"},
	},
	"addresses": {
		PaddleEndpoint: "/customers/{customer_id}/addresses",
		IDPrefix:       "add",
		DBTable:        "addresses",
		FieldMap:       map[string]string{},
		RequiredFields: []string{"customer_id", "country_code"},
	},
	"businesses": {
		PaddleEndpoint: "/customers/{customer_id}/businesses",
		IDPrefix:       "biz",
		DBTable:        "businesses",
		FieldMap:       map[string]string{},
		RequiredFields: []string{"customer_id", "name"},
	},
	"subscriptions": {
		PaddleEndpoint: "/subscriptions",
		IDPrefix:       "sub",
		DBTable:        "subscriptions",
		FieldMap: map[string]string{
			"id":         "",
			"paddle_id":  "id",
			"created_at": "created_at",
			"updated_at": "updated_at",
		},
		RequiredFields: []string{"customer_id", "address_id", "items"},
	},
	"transactions": {
		PaddleEndpoint: "/transactions",
		IDPrefix:       "txn",
		DBTable:        "transactions",
		FieldMap:       map[string]string{},
		RequiredFields: []string{"customer_id", "address_id", "items"},
	},
	"discounts": {
		PaddleEndpoint: "/discounts",
		IDPrefix:       "dsc",
		DBTable:        "discounts",
		FieldMap: map[string]string{
			"id":         "",
			"paddle_id":  "id",
			"created_at": "created_at",
			"updated_at": "updated_at",
		},
		RequiredFields: []string{"description", "type", "amount"},
	},
}

type SyncLayer struct {
	apiKey     string
	baseURL    string
	db         *sql.DB
	httpClient *http.Client
}

// Default API key - in production load from env
// For sandbox: get from https://sandbox-vendors.paddle.com/authentication
const DefaultAPIKey = "pdl_sdbx_apikey_01knegw36v6cvybp2y5652xpmq_weT2XzhV6Qk0rGEYDY0V5X_Aig"

// NewSyncLayer creates a sync layer with auto-detected sandbox mode
// Uses isProductionServer() from main.go to determine environment
func NewSyncLayer(apiKey string, db *sql.DB) *SyncLayer {
	if apiKey == "" {
		apiKey = DefaultAPIKey
	}

	// Auto-detect: if not on production server, use sandbox
	sandbox := !isProductionServer()
	if sandbox {
		fmt.Println("Using PADDLE SANDBOX environment")
	} else {
		fmt.Println("Using PADDLE LIVE environment")
	}

	baseURL := "https://api.paddle.com"
	if sandbox {
		baseURL = "https://sandbox-api.paddle.com"
	}

	return &SyncLayer{
		apiKey:     apiKey,
		baseURL:    baseURL,
		db:         db,
		httpClient: &http.Client{Timeout: 30 * time.Second},
	}
}

// SyncResult from dual-write operation
type SyncResult struct {
	Success     bool
	OurID       string                 // Our internal ID (generated)
	PaddleID    string                 // Paddle's returned ID
	Entity      string                 // Entity type
	Data        map[string]interface{} // Final merged data
	DBError     error
	PaddleError error
}

// Create syncs a new entity to both our DB and Paddle
func (s *SyncLayer) Create(entity string, data map[string]interface{}) SyncResult {
	mapping, ok := EntityRegistry[entity]
	if !ok {
		return SyncResult{Success: false, Entity: entity, DBError: fmt.Errorf("unknown entity: %s", entity)}
	}

	// 1. Validate required fields
	for _, field := range mapping.RequiredFields {
		if _, ok := data[field]; !ok {
			return SyncResult{Success: false, Entity: entity, DBError: fmt.Errorf("missing required field: %s", field)}
		}
	}

	// 2. Generate our internal ID
	ourID := fmt.Sprintf("%s_%d", mapping.IDPrefix, time.Now().UnixNano())
	data["id"] = ourID
	data["created_at"] = time.Now().Unix()
	data["updated_at"] = time.Now().Unix()
	data["sync_status"] = "pending"
	data["pending_since"] = time.Now().Unix() // Track for retry logic

	// 3. Build Paddle payload (map our fields to Paddle's if needed)
	paddlePayload := s.toPaddlePayload(data, mapping.FieldMap)

	// 4. Write to our DB first (always local first)
	if err := s.insertToDB(mapping.DBTable, data); err != nil {
		return SyncResult{Success: false, Entity: entity, OurID: ourID, DBError: err}
	}

	// 5. Determine endpoint (handle path params like {customer_id})
	endpoint := s.resolveEndpoint(mapping.PaddleEndpoint, data)

	// 6. Call Paddle API
	paddleResp, err := s.callPaddle("POST", endpoint, paddlePayload)
	if err != nil {
		// Update DB with error, will retry later
		s.db.Exec(fmt.Sprintf("UPDATE %s SET sync_status = 'error', sync_error = ? WHERE id = ?", mapping.DBTable),
			err.Error(), ourID)
		return SyncResult{Success: false, Entity: entity, OurID: ourID, PaddleError: err}
	}

	// 7. Extract Paddle ID from response
	paddleID := s.extractID(paddleResp)
	if paddleID == "" {
		// Strange - Paddle didn't return ID
		s.db.Exec(fmt.Sprintf("UPDATE %s SET sync_status = 'error', sync_error = ? WHERE id = ?", mapping.DBTable),
			"paddle did not return id", ourID)
		return SyncResult{Success: false, Entity: entity, OurID: ourID, PaddleError: fmt.Errorf("no id in paddle response")}
	}

	// 8. Update our DB with Paddle ID and synced status
	_, dbErr := s.db.Exec(fmt.Sprintf("UPDATE %s SET paddle_id = ?, sync_status = 'synced', sync_error = NULL WHERE id = ?", mapping.DBTable),
		paddleID, ourID)
	if dbErr != nil {
		// This is the worst case - Paddle created but we lost the ID
		return SyncResult{Success: false, Entity: entity, OurID: ourID, PaddleID: paddleID,
			DBError: fmt.Errorf("paddle created (%s) but DB update failed: %v", paddleID, dbErr)}
	}

	// 9. Merge Paddle's response data back into our record (includes IDs, timestamps, computed fields)
	mergedData := s.mergePaddleResponse(data, paddleResp, mapping.FieldMap)
	data["paddle_id"] = paddleID
	data["sync_status"] = "synced"
	data["last_paddle_sync_at"] = time.Now().Unix()
	data["pending_since"] = nil // Clear pending since we're synced

	// 10. Update our DB with merged data (Paddle may have added/modified fields)
	if err := s.updateDBWithMergedData(mapping.DBTable, ourID, mergedData); err != nil {
		// Log but don't fail - we have the core data
		fmt.Printf("Warning: failed to update merged data for %s: %v\n", ourID, err)
	}

	return SyncResult{Success: true, Entity: entity, OurID: ourID, PaddleID: paddleID, Data: mergedData}
}

// Update syncs changes to both systems
func (s *SyncLayer) Update(entity string, ourID string, data map[string]interface{}) SyncResult {
	mapping := EntityRegistry[entity]

	// Get current record to find Paddle ID
	var paddleID string
	row := s.db.QueryRow(fmt.Sprintf("SELECT paddle_id FROM %s WHERE id = ?", mapping.DBTable), ourID)
	row.Scan(&paddleID)

	if paddleID == "" {
		return SyncResult{Success: false, Entity: entity, OurID: ourID,
			PaddleError: fmt.Errorf("no paddle_id found, cannot update")}
	}

	// Update our DB
	data["updated_at"] = time.Now().Unix()
	if err := s.updateDB(mapping.DBTable, ourID, data); err != nil {
		return SyncResult{Success: false, Entity: entity, OurID: ourID, DBError: err}
	}

	// Update Paddle
	paddlePayload := s.toPaddlePayload(data, mapping.FieldMap)
	endpoint := mapping.PaddleEndpoint + "/" + paddleID
	_, err := s.callPaddle("PATCH", endpoint, paddlePayload)
	if err != nil {
		return SyncResult{Success: false, Entity: entity, OurID: ourID, PaddleID: paddleID, PaddleError: err}
	}

	return SyncResult{Success: true, Entity: entity, OurID: ourID, PaddleID: paddleID}
}

// RetryAll retries all pending/error syncs that are stale (> 5 minutes)
func (s *SyncLayer) RetryAll() {
	for entity := range EntityRegistry {
		// Only retry items pending for more than 5 minutes
		ids, err := s.FindStalePending(entity, 5)
		if err != nil {
			continue
		}

		for _, id := range ids {
			s.retryEntity(entity, id)
		}
	}
}

// RetryImmediate retries a specific entity immediately (for manual retry)
func (s *SyncLayer) RetryImmediate(entity, ourID string) {
	// Reset status to trigger retry
	s.db.Exec(fmt.Sprintf("UPDATE %s SET sync_status = 'pending', pending_since = ? WHERE id = ?", EntityRegistry[entity].DBTable),
		time.Now().Unix(), ourID)

	// Use the regular retry
	s.retryEntity(entity, ourID)
}

// Private helpers

func (s *SyncLayer) insertToDB(table string, data map[string]interface{}) error {
	columns := []string{}
	placeholders := []string{}
	values := []interface{}{}

	for col, val := range data {
		columns = append(columns, col)
		placeholders = append(placeholders, "?")
		values = append(values, val)
	}

	sql := fmt.Sprintf("INSERT INTO %s (%s) VALUES (%s)",
		table,
		strings.Join(columns, ", "),
		strings.Join(placeholders, ", "))

	_, err := s.db.Exec(sql, values...)
	return err
}

func (s *SyncLayer) updateDB(table string, id string, data map[string]interface{}) error {
	sets := []string{}
	values := []interface{}{}

	for col, val := range data {
		sets = append(sets, fmt.Sprintf("%s = ?", col))
		values = append(values, val)
	}
	values = append(values, id)

	sql := fmt.Sprintf("UPDATE %s SET %s WHERE id = ?",
		table,
		strings.Join(sets, ", "))

	_, err := s.db.Exec(sql, values...)
	return err
}

func (s *SyncLayer) toPaddlePayload(data map[string]interface{}, fieldMap map[string]string) map[string]interface{} {
	result := make(map[string]interface{})

	for ourField, val := range data {
		// Skip internal fields
		if ourField == "id" || ourField == "paddle_id" || ourField == "sync_status" || ourField == "sync_error" {
			continue
		}
		if ourField == "created_at" || ourField == "updated_at" || ourField == "pending_since" {
			continue
		}
		if ourField == "last_paddle_sync_at" || ourField == "paddle_event_id" || ourField == "internal_notes" {
			continue
		}

		// Map field name if needed
		paddleField := ourField
		if mapped, ok := fieldMap[ourField]; ok && mapped != "" {
			paddleField = mapped
		}

		result[paddleField] = val
	}

	return result
}

func (s *SyncLayer) resolveEndpoint(endpoint string, data map[string]interface{}) string {
	// Replace {customer_id} etc. with actual values
	result := endpoint
	for key, val := range data {
		placeholder := "{" + key + "}"
		if strVal, ok := val.(string); ok {
			result = strings.ReplaceAll(result, placeholder, strVal)
		}
	}
	return result
}

func (s *SyncLayer) callPaddle(method, endpoint string, payload map[string]interface{}) (map[string]interface{}, error) {
	url := s.baseURL + endpoint
	body, _ := json.Marshal(payload)

	req, err := http.NewRequest(method, url, bytes.NewBuffer(body))
	if err != nil {
		return nil, err
	}

	req.Header.Set("Authorization", "Bearer "+s.apiKey)
	req.Header.Set("Content-Type", "application/json")

	resp, err := s.httpClient.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	respBody, _ := io.ReadAll(resp.Body)

	if resp.StatusCode >= 400 {
		return nil, fmt.Errorf("paddle %s %d: %s", method, resp.StatusCode, string(respBody))
	}

	var result map[string]interface{}
	json.Unmarshal(respBody, &result)
	return result, nil
}

func (s *SyncLayer) extractID(response map[string]interface{}) string {
	// Paddle wraps response in "data": { "id": "..." }
	if data, ok := response["data"].(map[string]interface{}); ok {
		if id, ok := data["id"].(string); ok {
			return id
		}
	}
	return ""
}

func (s *SyncLayer) retryEntity(entity, ourID string) {
	// Simplified: just mark for retry by resetting status
	mapping := EntityRegistry[entity]
	s.db.Exec(fmt.Sprintf("UPDATE %s SET sync_status = 'pending' WHERE id = ?", mapping.DBTable), ourID)
}

// mergePaddleResponse merges Paddle's response data with our original data
// Maps Paddle field names back to our field names using reverse mapping
func (s *SyncLayer) mergePaddleResponse(ourData map[string]interface{}, paddleResp map[string]interface{}, fieldMap map[string]string) map[string]interface{} {
	result := make(map[string]interface{})

	// Start with our original data
	for k, v := range ourData {
		result[k] = v
	}

	// Extract Paddle's data object
	var paddleData map[string]interface{}
	if data, ok := paddleResp["data"].(map[string]interface{}); ok {
		paddleData = data
	} else {
		paddleData = paddleResp // Some responses aren't wrapped
	}

	// Build reverse field map (paddle_field → our_field)
	reverseMap := make(map[string]string)
	for ourField, paddleField := range fieldMap {
		if paddleField != "" {
			reverseMap[paddleField] = ourField
		}
	}

	// Merge Paddle fields, mapping names back to ours
	for paddleField, val := range paddleData {
		ourField := paddleField
		if mapped, ok := reverseMap[paddleField]; ok {
			ourField = mapped
		}

		// Don't overwrite our internal fields
		if ourField == "id" || ourField == "sync_status" || ourField == "sync_error" {
			continue
		}

		result[ourField] = val
	}

	return result
}

// updateDBWithMergedData updates our DB record with merged data from Paddle
func (s *SyncLayer) updateDBWithMergedData(table, ourID string, mergedData map[string]interface{}) error {
	sets := []string{}
	values := []interface{}{}

	for col, val := range mergedData {
		// Skip the ID field itself
		if col == "id" {
			continue
		}
		sets = append(sets, fmt.Sprintf("%s = ?", col))
		values = append(values, val)
	}
	values = append(values, ourID)

	sql := fmt.Sprintf("UPDATE %s SET %s WHERE id = ?",
		table,
		strings.Join(sets, ", "))

	_, err := s.db.Exec(sql, values...)
	return err
}

// HandleWebhook processes inbound updates from Paddle (subscriptions, status changes, etc.)
// Updates our DB to match Paddle's state
func (s *SyncLayer) HandleWebhook(entity string, paddleData map[string]interface{}) error {
	mapping, ok := EntityRegistry[entity]
	if !ok {
		return fmt.Errorf("unknown entity for webhook: %s", entity)
	}

	// Extract Paddle ID
	paddleID, ok := paddleData["id"].(string)
	if !ok {
		return fmt.Errorf("no id in webhook data")
	}

	// Extract event ID if present (for idempotency)
	eventID, _ := paddleData["event_id"].(string)

	// Find our record by Paddle ID
	var ourID string
	var existingEventID string
	err := s.db.QueryRow(
		fmt.Sprintf("SELECT id, paddle_event_id FROM %s WHERE paddle_id = ?", mapping.DBTable),
		paddleID,
	).Scan(&ourID, &existingEventID)

	if err != nil {
		return fmt.Errorf("no local record for paddle %s: %v", paddleID, err)
	}

	// Idempotency check: skip if we already processed this event
	if eventID != "" && existingEventID == eventID {
		return nil // Already processed
	}

	// Map Paddle fields to our fields
	ourData := make(map[string]interface{})
	for paddleField, val := range paddleData {
		ourField := paddleField
		// Check if this Paddle field maps to one of ours
		for ourF, paddleF := range mapping.FieldMap {
			if paddleF == paddleField && paddleF != "" {
				ourField = ourF
				break
			}
		}

		// Don't overwrite internal fields
		if ourField == "id" || ourField == "paddle_id" {
			continue
		}

		ourData[ourField] = val
	}

	// Update our record with webhook data
	ourData["updated_at"] = time.Now().Unix()
	ourData["sync_status"] = "synced" // Webhook confirms sync
	ourData["sync_error"] = nil
	ourData["last_paddle_sync_at"] = time.Now().Unix()
	ourData["pending_since"] = nil // Clear pending
	if eventID != "" {
		ourData["paddle_event_id"] = eventID
	}

	return s.updateDBWithMergedData(mapping.DBTable, ourID, ourData)
}

// FindStalePending finds records pending for more than X minutes
func (s *SyncLayer) FindStalePending(entity string, minutes int) ([]string, error) {
	mapping, ok := EntityRegistry[entity]
	if !ok {
		return nil, fmt.Errorf("unknown entity: %s", entity)
	}

	cutoff := time.Now().Add(-time.Duration(minutes) * time.Minute).Unix()

	rows, err := s.db.Query(
		fmt.Sprintf("SELECT id FROM %s WHERE sync_status = 'pending' AND pending_since < ?", mapping.DBTable),
		cutoff,
	)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var ids []string
	for rows.Next() {
		var id string
		rows.Scan(&id)
		ids = append(ids, id)
	}

	return ids, nil
}