package adapter

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

	"gitea.dwysokinski.me/twhelp/core/internal/bun/bunmodel"
	"gitea.dwysokinski.me/twhelp/core/internal/domain"
	"github.com/uptrace/bun"
)

type VersionBunRepository struct {
	db bun.IDB
}

func NewVersionBunRepository(db bun.IDB) *VersionBunRepository {
	return &VersionBunRepository{db: db}
}

func (repo *VersionBunRepository) List(
	ctx context.Context,
	params domain.ListVersionsParams,
) (domain.ListVersionsResult, error) {
	var versions bunmodel.Versions

	if err := repo.db.NewSelect().
		Model(&versions).
		Apply(listVersionsParamsApplier{params: params}.apply).
		Scan(ctx); err != nil && !errors.Is(err, sql.ErrNoRows) {
		return domain.ListVersionsResult{}, fmt.Errorf("couldn't select versions from the database: %w", err)
	}

	converted, err := versions.ToDomain()
	if err != nil {
		return domain.ListVersionsResult{}, err
	}

	return domain.NewListVersionsResult(separateListResultAndNext(converted, params.Limit()))
}

type listVersionsParamsApplier struct {
	params domain.ListVersionsParams
}

func (a listVersionsParamsApplier) apply(q *bun.SelectQuery) *bun.SelectQuery {
	if codes := a.params.Codes(); len(codes) > 0 {
		q = q.Where("version.code IN (?)", bun.In(codes))
	}

	for _, s := range a.params.Sort() {
		column, dir, err := a.sortToColumnAndDirection(s)
		if err != nil {
			return q.Err(err)
		}

		q.OrderExpr("? ?", column, dir.Bun())
	}

	return q.Limit(a.params.Limit() + 1).Apply(a.applyCursor)
}

func (a listVersionsParamsApplier) applyCursor(q *bun.SelectQuery) *bun.SelectQuery {
	cursor := a.params.Cursor()

	if cursor.IsZero() {
		return q
	}

	sort := a.params.Sort()
	cursorApplier := cursorPaginationApplier{
		data: make([]cursorPaginationApplierDataElement, 0, len(sort)),
	}

	for _, s := range sort {
		var err error
		var el cursorPaginationApplierDataElement

		el.column, el.direction, err = a.sortToColumnAndDirection(s)
		if err != nil {
			return q.Err(err)
		}

		switch s {
		case domain.VersionSortCodeASC,
			domain.VersionSortCodeDESC:
			el.value = cursor.Code()
			el.unique = true
		default:
			return q.Err(fmt.Errorf("%s: %w", s.String(), errInvalidSortValue))
		}

		cursorApplier.data = append(cursorApplier.data, el)
	}

	return q.Apply(cursorApplier.apply)
}

func (a listVersionsParamsApplier) sortToColumnAndDirection(
	s domain.VersionSort,
) (bun.Safe, sortDirection, error) {
	switch s {
	case domain.VersionSortCodeASC:
		return "version.code", sortDirectionASC, nil
	case domain.VersionSortCodeDESC:
		return "version.code", sortDirectionDESC, nil
	default:
		return "", 0, fmt.Errorf("%s: %w", s.String(), errInvalidSortValue)
	}
}