package tdb

import (
	"bytes"
	"errors"
	"fmt"
)

type uniqueConstraint struct {
	table *table
	field dbField
	index indexish
}

func newUniqueConstraint(table *table, index indexish, field dbField) (constraintish, error) {
	if table == nil {
		return nil, errors.New("[constraint] [unique] unable to create without table")
	}
	if index == nil {
		return nil, fmt.Errorf("[constraint] [unique] is only valid for indicies (to avoid full table scans)")
	}

	return &uniqueConstraint{
		table: table,
		field: field,
		index: index,
	}, nil
}

func (c *uniqueConstraint) validate(tx *Tx, pv dbPtrValue) error {
	indexedVals := c.index.indexedValues(pv)
	keyValue := c.index.keyValue(pv)
	for _, indexedVal := range indexedVals {
		if err := c.index.iteratePrefixed(tx, indexedVal, func(indexed []byte) (IterationSignal, error) {
			if !bytes.Equal(keyValue, indexed) {
				c.table.debugLogf("[constraint] [unique] violation: record with '%s'.'%s' = '%s' already exists (id: %s)", c.table.name, c.field.Name, indexedVal, indexed)
				return StopIteration, fmt.Errorf("[constraint] [unique] violation for field '%s'.'%s'", c.table.name, c.field.Name)
			}
			return StopIteration, nil
		}); err != nil {
			return err
		}
	}
	return nil
}