package grpcserver

import (
	"context"
	"database/sql"
	"time"

	pb "git.wntrmute.dev/kyle/eng-pad-server/gen/engpad/v1"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"
	"google.golang.org/protobuf/types/known/timestamppb"
)

type SyncService struct {
	pb.UnimplementedEngPadSyncServiceServer
	DB      *sql.DB
	BaseURL string
}

const maxTotalStrokes = 100000

func (s *SyncService) SyncNotebook(ctx context.Context, req *pb.SyncNotebookRequest) (*pb.SyncNotebookResponse, error) {
	userID, ok := UserIDFromContext(ctx)
	if !ok {
		return nil, status.Error(codes.Internal, "missing user context")
	}

	// Validate page_size
	if req.PageSize != "REGULAR" && req.PageSize != "LARGE" {
		return nil, status.Errorf(codes.InvalidArgument, "invalid page_size: must be REGULAR or LARGE")
	}

	// Validate total stroke count and point_data alignment
	totalStrokes := 0
	for _, page := range req.Pages {
		totalStrokes += len(page.Strokes)
		if totalStrokes > maxTotalStrokes {
			return nil, status.Errorf(codes.InvalidArgument, "total stroke count exceeds maximum of %d", maxTotalStrokes)
		}
		for _, stroke := range page.Strokes {
			if len(stroke.PointData)%4 != 0 {
				return nil, status.Errorf(codes.InvalidArgument, "point_data length must be a multiple of 4")
			}
		}
	}

	tx, err := s.DB.BeginTx(ctx, nil)
	if err != nil {
		return nil, status.Errorf(codes.Internal, "begin tx: %v", err)
	}
	defer func() { _ = tx.Rollback() }()

	now := time.Now().UnixMilli()

	// Upsert notebook
	var notebookID int64
	err = tx.QueryRowContext(ctx,
		"SELECT id FROM notebooks WHERE user_id = ? AND remote_id = ?",
		userID, req.NotebookId,
	).Scan(&notebookID)

	if err == sql.ErrNoRows {
		res, err := tx.ExecContext(ctx,
			"INSERT INTO notebooks (user_id, remote_id, title, page_size, synced_at) VALUES (?, ?, ?, ?, ?)",
			userID, req.NotebookId, req.Title, req.PageSize, now,
		)
		if err != nil {
			return nil, status.Errorf(codes.Internal, "insert notebook: %v", err)
		}
		notebookID, _ = res.LastInsertId()
	} else if err != nil {
		return nil, status.Errorf(codes.Internal, "query notebook: %v", err)
	} else {
		// Update existing — delete all pages (cascade deletes strokes)
		if _, err := tx.ExecContext(ctx, "DELETE FROM pages WHERE notebook_id = ?", notebookID); err != nil {
			return nil, status.Errorf(codes.Internal, "delete pages: %v", err)
		}
		if _, err := tx.ExecContext(ctx,
			"UPDATE notebooks SET title = ?, page_size = ?, synced_at = ? WHERE id = ?",
			req.Title, req.PageSize, now, notebookID,
		); err != nil {
			return nil, status.Errorf(codes.Internal, "update notebook: %v", err)
		}
	}

	// Insert pages and strokes
	for _, page := range req.Pages {
		res, err := tx.ExecContext(ctx,
			"INSERT INTO pages (notebook_id, remote_id, page_number) VALUES (?, ?, ?)",
			notebookID, page.PageId, page.PageNumber,
		)
		if err != nil {
			return nil, status.Errorf(codes.Internal, "insert page: %v", err)
		}
		pageID, _ := res.LastInsertId()

		for _, stroke := range page.Strokes {
			if _, err := tx.ExecContext(ctx,
				"INSERT INTO strokes (page_id, pen_size, color, style, point_data, stroke_order) VALUES (?, ?, ?, ?, ?, ?)",
				pageID, stroke.PenSize, stroke.Color, stroke.Style, stroke.PointData, stroke.StrokeOrder,
			); err != nil {
				return nil, status.Errorf(codes.Internal, "insert stroke: %v", err)
			}
		}
	}

	if err := tx.Commit(); err != nil {
		return nil, status.Errorf(codes.Internal, "commit: %v", err)
	}

	return &pb.SyncNotebookResponse{
		ServerNotebookId: notebookID,
		SyncedAt:         timestamppb.Now(),
	}, nil
}

func (s *SyncService) GetNotebook(ctx context.Context, req *pb.GetNotebookRequest) (*pb.GetNotebookResponse, error) {
	userID, ok := UserIDFromContext(ctx)
	if !ok {
		return nil, status.Error(codes.Internal, "missing user context")
	}

	var resp pb.GetNotebookResponse
	var syncedAt int64
	err := s.DB.QueryRowContext(ctx,
		"SELECT id, remote_id, title, page_size, synced_at FROM notebooks WHERE id = ? AND user_id = ?",
		req.NotebookId, userID,
	).Scan(&resp.ServerNotebookId, &resp.RemoteId, &resp.Title, &resp.PageSize, &syncedAt)
	if err == sql.ErrNoRows {
		return nil, status.Error(codes.NotFound, "notebook not found")
	}
	if err != nil {
		return nil, status.Errorf(codes.Internal, "query notebook: %v", err)
	}
	resp.SyncedAt = timestamppb.New(time.UnixMilli(syncedAt))

	pageRows, err := s.DB.QueryContext(ctx,
		"SELECT id, remote_id, page_number FROM pages WHERE notebook_id = ? ORDER BY page_number",
		resp.ServerNotebookId,
	)
	if err != nil {
		return nil, status.Errorf(codes.Internal, "query pages: %v", err)
	}
	defer func() { _ = pageRows.Close() }()

	for pageRows.Next() {
		var pageID, remoteID int64
		var pageNum int32
		if err := pageRows.Scan(&pageID, &remoteID, &pageNum); err != nil {
			return nil, status.Errorf(codes.Internal, "scan page: %v", err)
		}

		pd := &pb.PageData{
			PageId:     remoteID,
			PageNumber: pageNum,
		}

		strokeRows, err := s.DB.QueryContext(ctx,
			"SELECT pen_size, color, style, point_data, stroke_order FROM strokes WHERE page_id = ? ORDER BY stroke_order",
			pageID,
		)
		if err != nil {
			return nil, status.Errorf(codes.Internal, "query strokes: %v", err)
		}

		for strokeRows.Next() {
			var sd pb.StrokeData
			if err := strokeRows.Scan(&sd.PenSize, &sd.Color, &sd.Style, &sd.PointData, &sd.StrokeOrder); err != nil {
				_ = strokeRows.Close()
				return nil, status.Errorf(codes.Internal, "scan stroke: %v", err)
			}
			pd.Strokes = append(pd.Strokes, &sd)
		}
		_ = strokeRows.Close()

		resp.Pages = append(resp.Pages, pd)
	}

	return &resp, nil
}

func (s *SyncService) DeleteNotebook(ctx context.Context, req *pb.DeleteNotebookRequest) (*pb.DeleteNotebookResponse, error) {
	userID, ok := UserIDFromContext(ctx)
	if !ok {
		return nil, status.Error(codes.Internal, "missing user context")
	}

	_, err := s.DB.ExecContext(ctx,
		"DELETE FROM notebooks WHERE user_id = ? AND remote_id = ?",
		userID, req.NotebookId,
	)
	if err != nil {
		return nil, status.Errorf(codes.Internal, "delete: %v", err)
	}

	return &pb.DeleteNotebookResponse{}, nil
}

func (s *SyncService) ListNotebooks(ctx context.Context, req *pb.ListNotebooksRequest) (*pb.ListNotebooksResponse, error) {
	userID, ok := UserIDFromContext(ctx)
	if !ok {
		return nil, status.Error(codes.Internal, "missing user context")
	}

	rows, err := s.DB.QueryContext(ctx,
		`SELECT n.id, n.remote_id, n.title, n.page_size, n.synced_at,
		        (SELECT COUNT(*) FROM pages WHERE notebook_id = n.id) as page_count
		 FROM notebooks n WHERE n.user_id = ? ORDER BY n.synced_at DESC`,
		userID,
	)
	if err != nil {
		return nil, status.Errorf(codes.Internal, "query: %v", err)
	}
	defer func() { _ = rows.Close() }()

	var notebooks []*pb.NotebookSummary
	for rows.Next() {
		var nb pb.NotebookSummary
		var syncedAt int64
		if err := rows.Scan(&nb.ServerId, &nb.RemoteId, &nb.Title, &nb.PageSize, &syncedAt, &nb.PageCount); err != nil {
			return nil, status.Errorf(codes.Internal, "scan: %v", err)
		}
		nb.SyncedAt = timestamppb.New(time.UnixMilli(syncedAt))
		notebooks = append(notebooks, &nb)
	}

	return &pb.ListNotebooksResponse{Notebooks: notebooks}, nil
}