package store

import (
	"context"
	"database/sql"
	"fmt"

	"github.com/M1ngdaXie/realtime-collab/internal/models"
	"github.com/google/uuid"
)

// CreateDocumentVersion creates a new version snapshot
func (s *PostgresStore) CreateDocumentVersion(
	ctx context.Context,
	documentID, userID uuid.UUID,
	snapshot []byte,
	textPreview *string,
	label *string,
	isAuto bool,
) (*models.DocumentVersion, error) {
	tx, err := s.db.BeginTx(ctx, nil)
	if err != nil {
		return nil, fmt.Errorf("failed to begin transaction: %w", err)
	}
	defer tx.Rollback()

	// Get next version number
	var versionNumber int
	err = tx.QueryRowContext(ctx,
		`SELECT get_next_version_number($1)`,
		documentID,
	).Scan(&versionNumber)
	if err != nil {
		return nil, fmt.Errorf("failed to get version number: %w", err)
	}

	// Insert version
	query := `
		INSERT INTO document_versions 
			(document_id, yjs_snapshot, text_preview, version_number, created_by, version_label, is_auto_generated)
		VALUES ($1, $2, $3, $4, $5, $6, $7)
		RETURNING id, document_id, text_preview, version_number, created_by, version_label, is_auto_generated, created_at
	`

	var version models.DocumentVersion
	err = tx.QueryRowContext(ctx, query,
		documentID, snapshot, textPreview, versionNumber, userID, label, isAuto,
	).Scan(
		&version.ID, &version.DocumentID, &version.TextPreview, &version.VersionNumber,
		&version.CreatedBy, &version.VersionLabel, &version.IsAutoGenerated, &version.CreatedAt,
	)
	if err != nil {
		return nil, fmt.Errorf("failed to create version: %w", err)
	}

	// Update document metadata
	_, err = tx.ExecContext(ctx, `
		UPDATE documents 
		SET version_count = version_count + 1, 
			last_snapshot_at = NOW() 
		WHERE id = $1
	`, documentID)
	if err != nil {
		return nil, fmt.Errorf("failed to update document metadata: %w", err)
	}

	if err := tx.Commit(); err != nil {
		return nil, fmt.Errorf("failed to commit transaction: %w", err)
	}

	return &version, nil
}

// ListDocumentVersions returns paginated version list with author info
func (s *PostgresStore) ListDocumentVersions(
	ctx context.Context,
	documentID uuid.UUID,
	limit int,
	offset int,
) ([]models.DocumentVersionWithAuthor, int, error) {
	// Get total count
	var total int
	err := s.db.QueryRowContext(ctx,
		`SELECT COUNT(*) FROM document_versions WHERE document_id = $1`,
		documentID,
	).Scan(&total)
	if err != nil {
		return nil, 0, fmt.Errorf("failed to count versions: %w", err)
	}

	// Get paginated versions with author (LEFT JOIN to handle deleted users)
	query := `
		SELECT 
			v.id, v.document_id, v.text_preview, v.version_number, 
			v.created_by, v.version_label, v.is_auto_generated, v.created_at,
			u.id, u.email, u.name, u.avatar_url
		FROM document_versions v
		LEFT JOIN users u ON v.created_by = u.id
		WHERE v.document_id = $1
		ORDER BY v.version_number DESC
		LIMIT $2 OFFSET $3
	`

	rows, err := s.db.QueryContext(ctx, query, documentID, limit, offset)
	if err != nil {
		return nil, 0, fmt.Errorf("failed to list versions: %w", err)
	}
	defer rows.Close()

	var versions []models.DocumentVersionWithAuthor
	for rows.Next() {
		var v models.DocumentVersionWithAuthor
		var authorID, authorEmail, authorName sql.NullString
		var authorAvatar *string

		err := rows.Scan(
			&v.ID, &v.DocumentID, &v.TextPreview, &v.VersionNumber,
			&v.CreatedBy, &v.VersionLabel, &v.IsAutoGenerated, &v.CreatedAt,
			&authorID, &authorEmail, &authorName, &authorAvatar,
		)
		if err != nil {
			return nil, 0, fmt.Errorf("failed to scan version: %w", err)
		}

		// Populate author if exists
		if authorID.Valid {
			authorUUID, _ := uuid.Parse(authorID.String)
			v.Author = &models.User{
				ID:        authorUUID,
				Email:     authorEmail.String,
				Name:      authorName.String,
				AvatarURL: authorAvatar,
			}
		}

		versions = append(versions, v)
	}

	return versions, total, nil
}

// GetDocumentVersion retrieves a specific version with full snapshot
func (s *PostgresStore) GetDocumentVersion(ctx context.Context, versionID uuid.UUID) (*models.DocumentVersion, error) {
	query := `
		SELECT id, document_id, yjs_snapshot, text_preview, version_number,
		       created_by, version_label, is_auto_generated, created_at
		FROM document_versions
		WHERE id = $1
	`

	var version models.DocumentVersion
	err := s.db.QueryRowContext(ctx, query, versionID).Scan(
		&version.ID, &version.DocumentID, &version.YjsSnapshot, &version.TextPreview,
		&version.VersionNumber, &version.CreatedBy, &version.VersionLabel,
		&version.IsAutoGenerated, &version.CreatedAt,
	)

	if err == sql.ErrNoRows {
		return nil, fmt.Errorf("version not found")
	}
	if err != nil {
		return nil, fmt.Errorf("failed to get version: %w", err)
	}

	return &version, nil
}

// GetLatestDocumentVersion gets the most recent version for auto-snapshot comparison
func (s *PostgresStore) GetLatestDocumentVersion(ctx context.Context, documentID uuid.UUID) (*models.DocumentVersion, error) {
	query := `
		SELECT id, document_id, yjs_snapshot, text_preview, version_number,
		       created_by, version_label, is_auto_generated, created_at
		FROM document_versions
		WHERE document_id = $1
		ORDER BY version_number DESC
		LIMIT 1
	`

	var version models.DocumentVersion
	err := s.db.QueryRowContext(ctx, query, documentID).Scan(
		&version.ID, &version.DocumentID, &version.YjsSnapshot, &version.TextPreview,
		&version.VersionNumber, &version.CreatedBy, &version.VersionLabel,
		&version.IsAutoGenerated, &version.CreatedAt,
	)

	if err == sql.ErrNoRows {
		return nil, nil // No versions yet
	}
	if err != nil {
		return nil, fmt.Errorf("failed to get latest version: %w", err)
	}

	return &version, nil
}