package postgresql

import (
	"git.hexq.cn/tiglog/mydb"
	"git.hexq.cn/tiglog/mydb/internal/sqladapter"
)

type collectionAdapter struct {
}

func (*collectionAdapter) Insert(col sqladapter.Collection, item interface{}) (interface{}, error) {
	pKey, err := col.PrimaryKeys()
	if err != nil {
		return nil, err
	}

	q := col.SQL().InsertInto(col.Name()).Values(item)

	if len(pKey) == 0 {
		// There is no primary key.
		res, err := q.Exec()
		if err != nil {
			return nil, err
		}

		// Attempt to use LastInsertId() (probably won't work, but the Exec()
		// succeeded, so we can safely ignore the error from LastInsertId()).
		lastID, err := res.LastInsertId()
		if err != nil {
			return nil, nil
		}
		return lastID, nil
	}

	// Asking the database to return the primary key after insertion.
	q = q.Returning(pKey...)

	var keyMap mydb.Cond
	if err := q.Iterator().One(&keyMap); err != nil {
		return nil, err
	}

	// The IDSetter interface does not match, look for another interface match.
	if len(keyMap) == 1 {
		return keyMap[pKey[0]], nil
	}

	// This was a compound key and no interface matched it, let's return a map.
	return keyMap, nil
}