package link

import (
	"context"
	"errors"
	"github.com/jackc/pgtype"
	"github.com/jackc/pgx/v4"
	"github.com/jackc/pgx/v4/pgxpool"
	"net/url"
	"time"
)

type Repository interface {
	Save(link *Link) error
	FindById(id string) (*Link, error)
	FindAll(limit int, offset int) (Links, error)
	DeleteById(id string) error
}

type PgRepository struct {
	pool *pgxpool.Pool
}

func (r *PgRepository) Save(link *Link) error {
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()

	tx, err := r.pool.Begin(ctx)
	if err != nil {
		return err
	}

	sql := `
		INSERT INTO links (id, name, redirect_url, creation_time) 
		VALUES ($1, $2, $3, $4::timestamp)
	`

	_, err = tx.Exec(ctx, sql, link.Id, link.Name, link.RedirectURL.String(), link.CreationTime.Format("2006-01-02 15:04:05"))
	if err != nil {
		_ = tx.Rollback(ctx)
		return err
	}

	if err = tx.Commit(ctx); err != nil {
		return err
	}

	return nil
}

func (r *PgRepository) FindById(id string) (*Link, error) {
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()

	tx, err := r.pool.Begin(ctx)
	if err != nil {
		return nil, err
	}

	sql := `
		SELECT id, name, redirect_url, creation_time
		FROM links
		WHERE id = $1
	`

	entity, err := mapRowToEntity(tx.QueryRow(ctx, sql, id))
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, nil
		} else {
			_ = tx.Rollback(ctx)
			return nil, err
		}
	}

	if err = tx.Commit(ctx); err != nil {
		return nil, err
	}

	return entity, nil
}

func (r *PgRepository) FindAll(limit int, offset int) (Links, error) {
	if limit < 0 {
		return nil, errors.New("limit can't be negative")
	}
	if offset < 0 {
		return nil, errors.New("offset can't be negative")
	}

	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()

	tx, err := r.pool.Begin(ctx)
	if err != nil {
		return nil, err
	}

	sql := `
		SELECT id, name, redirect_url, creation_time
		FROM links
		LIMIT $1
		OFFSET $2
	`

	rows, err := tx.Query(ctx, sql, limit, offset)
	if err != nil {
		_ = tx.Rollback(ctx)
		return nil, err
	}
	defer rows.Close()

	links := make(Links, 0)
	for rows.Next() {
		link, err := mapRowToEntity(rows)
		if err != nil {
			_ = tx.Rollback(ctx)
			return nil, err
		}

		links = append(links, link)
	}

	if err = rows.Err(); err != nil {
		_ = tx.Rollback(ctx)
		return nil, err
	}

	if err = tx.Commit(ctx); err != nil {
		return nil, err
	}

	return links, nil
}

func (r *PgRepository) DeleteById(id string) error {
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()

	tx, err := r.pool.Begin(ctx)
	if err != nil {
		return err
	}

	sql := `
		DELETE FROM links WHERE id = $1
	`

	_, err = tx.Exec(ctx, sql, id)
	if err != nil {
		_ = tx.Rollback(ctx)
		return err
	}

	if err = tx.Commit(ctx); err != nil {
		return err
	}

	return nil
}

func mapRowToEntity(r interface{}) (*Link, error) {
	var entity Link
	var urlStr string
	var t pgtype.Timestamp

	switch v := r.(type) {
	case pgx.Row:
		if err := v.Scan(&entity.Id, &entity.Name, &urlStr, &t); err != nil {
			return nil, err
		}
	case pgx.Rows:
		if err := v.Scan(&entity.Id, &entity.Name, &urlStr, &t); err != nil {
			return nil, err
		}
	default:
		return nil, errors.New("unsupported type")
	}

	u, err := url.Parse(urlStr)
	if err != nil {
		return nil, err
	}

	entity.RedirectURL = *u
	entity.CreationTime = t.Time

	return &entity, nil
}