package parse

import (
	"encoding/json"
	"errors"
	"fmt"
	"io"

	"go.mongodb.org/mongo-driver/v2/bson"
)

type Op struct {
	UseTx bool     `json:"tx"`
	Cmds  []bson.D `json:"cmds"`
}

type JSONMigration struct {
	Up   Op `json:"up"`
	Down Op `json:"down"`
}

func JSON(r io.Reader) (*JSONMigration, error) {
	bytes, err := io.ReadAll(r)
	if err != nil {
		return nil, err
	}

	var jf JSONMigration
	if err := json.Unmarshal(bytes, &jf); err != nil {
		return nil, err
	}
	if len(jf.Up.Cmds) == 0 {
		return nil, errors.New("missing 'up' commands")
	}
	if len(jf.Down.Cmds) == 0 {
		return nil, errors.New("missing 'down' commands")
	}

	if jf.Up.UseTx != jf.Down.UseTx {
		return nil, fmt.Errorf("up and down statements must have the same transaction mode")
	}
	return &jf, nil
}