package user

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"log"
	"log/slog"
	"net/http"
	"os"
	"time"

	"crussell/db"
	"crussell/handlers/payments"
	"crussell/internal/dav"
	"crussell/internal/s3"
	"crussell/internal/square"
	"crussell/mw"

	"github.com/jackc/pgx/v5"
)

// DELETE /api/user/account
func DeleteAccountHandler(w http.ResponseWriter, r *http.Request) {
	userID, ok := mw.GetUserID(r.Context())
	if !ok {
		http.Error(w, "unauthorized", http.StatusUnauthorized)
		return
	}

	var accountRole string
	var profilePicURL sql.NullString
	err := db.Conn.QueryRow(r.Context(), `SELECT account_role, profile_pic_url FROM users WHERE id = $1`, userID).
		Scan(&accountRole, &profilePicURL)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			http.Error(w, "user not found", http.StatusNotFound)
			return
		}
		log.Printf("Failed to fetch user for deletion: %v", err)
		http.Error(w, "server error", http.StatusInternalServerError)
		return
	}

	ctx := r.Context()

	// --- External system scrubbing (BEFORE SQL anonymize) ---

	// Delete profile picture from S3/R2
	if profilePicURL.Valid && profilePicURL.String != "" && s3.Client != nil {
		// #nosec G118 — intentional background goroutine for async profile pic cleanup
		go func(picURL string) {
			defer func() {
				if r := recover(); r != nil {
					log.Printf("Panic recovered in S3 profile picture deletion: %v", r)
				}
			}()
			ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
			defer cancel()
			bucket := os.Getenv("S3_PROFILE_PICS_BUCKET")
			if bucket == "" {
				bucket = "crussell-profile-pics"
			}
			// profiles/{userID}.jpg — matches UploadProfilePictureHandler key format
			key := fmt.Sprintf("profiles/%s.jpg", userID)
			if err := s3.Client.Delete(ctx, bucket, key); err != nil {
				log.Printf("Warning: Failed to delete profile picture for user %s: %v", userID, err)
			}
		}(profilePicURL.String)
	}

	// Snapshot the Square card IDs AND customer IDs synchronously BEFORE the
	// SQL anonymization below NULLs square_card_id/square_customer_id, so the
	// background cleanup still has the external Square references it needs
	// (previously the goroutine read the rows itself, racing the anonymize
	// step which wiped them mid-flight). Distinct non-null customer IDs only:
	// a user's saved cards share one provisioned Square customer, so
	// DeleteCustomer runs once per customer. NULL customer IDs (users with
	// no saved cards) are skipped.
	var cardIDs []string
	customerSeen := map[string]bool{}
	var customerIDs []string
	// Capture the client synchronously so the async cleanup goroutine never
	// reads the global payments.SquareClient (which tests swap per-account).
	sqClient := payments.SquareClient
	if sqClient != nil {
		rows, err := db.Conn.Query(r.Context(),
			`SELECT square_card_id, square_customer_id FROM user_saved_cards WHERE user_id = $1 AND deleted_at IS NULL`, userID)
		if err != nil {
			log.Printf("Warning: Failed to query saved cards for user %s: %v", userID, err)
		} else {
			for rows.Next() {
				var cardID, customerID sql.NullString
				if err := rows.Scan(&cardID, &customerID); err != nil {
					log.Printf("Warning: Failed to scan card ID for user %s: %v", userID, err)
					continue
				}
				if cardID.Valid && cardID.String != "" {
					cardIDs = append(cardIDs, cardID.String)
				}
				if customerID.Valid && customerID.String != "" && !customerSeen[customerID.String] {
					customerSeen[customerID.String] = true
					customerIDs = append(customerIDs, customerID.String)
				}
			}
			if err := rows.Err(); err != nil {
				log.Printf("Warning: Row iteration error for user %s: %v", userID, err)
			}
			rows.Close()
		}
	}

	// --- SQL-level anonymization/deletion ---

	if accountRole == "guest" {
		tx, err := db.Conn.Begin(ctx)
		if err != nil {
			log.Printf("Failed to begin transaction for guest user deletion: %v", err)
			http.Error(w, "server error", http.StatusInternalServerError)
			return
		}
		defer func() {
			if err := tx.Rollback(ctx); err != nil && !errors.Is(err, pgx.ErrTxClosed) {
				slog.Error("failed to rollback transaction", "err", err)
			}
		}()

		_, err = tx.Exec(ctx, `SELECT delete_guest_user($1)`, userID)
		if err != nil {
			log.Printf("Failed to delete guest user %s: %v", userID, err)
			http.Error(w, "server error", http.StatusInternalServerError)
			return
		}

		if err := tx.Commit(ctx); err != nil {
			log.Printf("Failed to commit transaction for guest user deletion: %v", err)
			http.Error(w, "server error", http.StatusInternalServerError)
			return
		}
	} else {
		tx, err := db.Conn.Begin(ctx)
		if err != nil {
			log.Printf("Failed to begin transaction for user anonymization: %v", err)
			http.Error(w, "server error", http.StatusInternalServerError)
			return
		}
		defer func() {
			if err := tx.Rollback(ctx); err != nil && !errors.Is(err, pgx.ErrTxClosed) {
				slog.Error("failed to rollback transaction", "err", err)
			}
		}()

		// anonymize_user() is the single source of truth for erasure: it NULLs
		// the 2FA columns and staff notes in the same statement that anonymizes
		// the rest of the row, so every call site (this handler AND the
		// idle-account batch cleanup in scheduling.CleanupIdleAccounts) is
		// GDPR-clean without a separate Go-side scrub.
		_, err = tx.Exec(ctx, `SELECT anonymize_user($1)`, userID)
		if err != nil {
			log.Printf("Failed to anonymize user %s: %v", userID, err)
			http.Error(w, "server error", http.StatusInternalServerError)
			return
		}

		if err := tx.Commit(ctx); err != nil {
			log.Printf("Failed to commit transaction for user anonymization: %v", err)
			http.Error(w, "server error", http.StatusInternalServerError)
			return
		}

		// TODO: Create 'user_anonymized' notification for admin audit trail
	}

	// The local erasure committed: drop the user's cached Square customer id so
	// the erased identity cannot resurface from the process-local cache on a
	// later save-card flow (the Square customer is deleted below and the DB
	// columns are NULLed, but the cache is never touched by either).
	payments.InvalidateSquareCustomerCache(userID)

	// external Square cleanup fires only after local anonymization/deletion
	// commits, so a failed local tx leaves external state intact for retry.
	if sqClient != nil && (len(cardIDs) > 0 || len(customerIDs) > 0) {
		// #nosec G118 — intentional background goroutine for async account deletion
		go func(client square.SquareClient, cards, customers []string) {
			defer func() {
				if r := recover(); r != nil {
					log.Printf("Panic recovered in Square cleanup: %v", r)
				}
			}()
			ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
			defer cancel()
			for _, cardID := range cards {
				if err := client.DeleteCardOnFile(ctx, cardID); err != nil {
					// TokenPrefix redacts the ccof: card token — the full ID must
					// never reach logs.
					log.Printf("Warning: Failed to delete Square card %s for user %s: %v", square.TokenPrefix(cardID), userID, err)
				}
			}
			for _, customerID := range customers {
				// Square customers are provisioned per-user from a deterministic
				// email-derived key, but the UNIQUE(email) index excludes guest
				// accounts — so a guest and a registered user sharing an email can
				// end up on the SAME Square customer profile (Square dedups within
				// its idempotency window). Deleting it would break the other
				// account's saved-card charges, so skip the deletion when any OTHER
				// non-deleted saved card still references the customer.
				var stillReferenced bool
				if err := db.Conn.QueryRow(ctx, `
					SELECT EXISTS(SELECT 1 FROM user_saved_cards WHERE square_customer_id = $1 AND user_id <> $2 AND deleted_at IS NULL)
				`, customerID, userID).Scan(&stillReferenced); err != nil {
					log.Printf("Warning: Failed to check Square customer %s references before deletion: %v", square.TokenPrefix(customerID), err)
					continue
				}
				if stillReferenced {
					// PII-redacted customer id — the full id never reaches logs.
					log.Printf("Warning: skipping Square customer deletion — customer %s still referenced by another account", square.TokenPrefix(customerID))
					continue
				}
				if err := client.DeleteCustomer(ctx, customerID); err != nil {
					log.Printf("Warning: Failed to delete Square customer %s for user %s: %v", square.TokenPrefix(customerID), userID, err)
				}
			}
		}(sqClient, cardIDs, customerIDs)
	}

	// Delete CardDAV contact (non-blocking, best-effort)
	if dav.Service != nil {
		go func() {
			defer func() {
				if r := recover(); r != nil {
					log.Printf("Panic recovered in CardDAV contact deletion: %v", r)
				}
			}()
			uri := fmt.Sprintf("%s.vcf", userID)
			if err := dav.Service.DeleteContact(1, uri); err != nil {
				log.Printf("Warning: Failed to delete CardDAV contact for user %s: %v", userID, err)
			}
		}()
	}

	w.WriteHeader(http.StatusNoContent)
}