package tdb

import (
	"errors"
	"fmt"

	"git.keganmyers.com/terribleplan/tdb/stringy"

	bolt "go.etcd.io/bbolt"
)

type foreignConstraint struct {
	domestic *table
	foreign  *table
	field    dbField
	index    indexish
}
type foreignSimpleConstraint foreignConstraint
type foreignArrayConstraint foreignConstraint

func validateForeignRaw(b *bolt.Bucket, foreignKey []byte) ConstraintValidationStatus {
	if b.Get(foreignKey) == nil {
		return ConstraintViolation
	}
	return ConstraintValidated
}

func newSimpleForeignConstraint(domestic *table, foreign string, field dbField, index indexish) (constraintish, error) {
	if domestic == nil {
		return nil, errors.New("[constraint] [foreign] unable to create: no domestic table")
	}

	if !field.IsUint64() {
		return nil, fmt.Errorf("[constraint] [foreign] unable to create: '%s'.'%s' is not a uint64", domestic.name, field.Name)
	}

	if foreign == "" {
		return nil, errors.New("[constraint] [foreign] unable to create: no foreign table")
	}
	foreignTable, ok := domestic.db.tables[foreign]
	if !ok {
		return nil, fmt.Errorf("[constraint] [foreign] unable to create: no such table '%s'", foreign)
	}

	if index == nil {
		domestic.debugLogf("[constraint] [foreign] warning: creating constraint on '%s'.'%s' without index. will not check when foreign records are removed (to avoid table scan)", domestic.name, field.Name)
	}

	return &foreignSimpleConstraint{
		domestic: domestic,
		foreign:  foreignTable,
		field:    field,
		index:    index,
	}, nil
}

func (c *foreignSimpleConstraint) validate(tx *Tx, pv dbPtrValue) error { // foreign keys must all be uint64, those are the only supported primary keys
	foreignId := pv.dangerous_Field(c.field).Uint()

	// the foreign constraint is not responsible for enforcing nullability
	if foreignId == 0 {
		return nil
	}

	foreignKey := []byte(stringy.LiteralUintToString(foreignId))
	if validateForeignRaw(c.foreign.bucket(tx), foreignKey) == ConstraintViolation {
		c.domestic.debugLogf("[constraint] [foreign] violation: '%s' with Id '%s' does not exist", c.foreign.name, foreignKey)
		return fmt.Errorf("[constraint] [foreign] violation: '%s' with Id '%s' does not exist", c.foreign.name, foreignKey)
	}
	return nil
}

func newArrayForeignConstraint(domestic *table, foreign string, field dbField, index indexish) (constraintish, error) {
	if domestic == nil {
		return nil, errors.New("[constraint] [foreign] unable to create: no domestic table")
	}

	if !field.IsUint64Slice() {
		return nil, fmt.Errorf("[constraint] [foreign] unable to create: '%s'.'%s' is not a uint64 array", domestic.name, field.Name)
	}

	if foreign == "" {
		return nil, errors.New("[constraint] [foreign] unable to create: no foreign table")
	}
	foreignTable, ok := domestic.db.tables[foreign]
	if !ok {
		return nil, fmt.Errorf("[constraint] [foreign] unable to create: no such table '%s'", foreign)
	}

	if index == nil {
		domestic.debugLogf("[constraint] [foreign] warning: creating constraint on '%s'.'%s' without index. will not check when foreign records are removed (to avoid table scan)", domestic.name, field.Name)
	}

	return &foreignArrayConstraint{
		domestic: domestic,
		foreign:  foreignTable,
		field:    field,
		index:    index,
	}, nil
}

func (c *foreignArrayConstraint) validate(tx *Tx, pv dbPtrValue) error { // foreign keys must all be uint64, those are the only supported primary keys
	foreignIds := pv.dangerous_Field(c.field)

	foreignIdsLen := foreignIds.Len()
	for i := 0; i < foreignIdsLen; i++ {
		foreignId := foreignIds.Index(i).Uint()
		// the foreign constraint is not responsible for enforcing nullability
		if foreignId == 0 {
			continue
		}

		foreignKey := []byte(stringy.LiteralUintToString(foreignId))
		if validateForeignRaw(c.foreign.bucket(tx), foreignKey) == ConstraintViolation {
			c.domestic.debugLogf("[constraint] [foreign] violation: '%s' with Id '%s' does not exist", c.foreign.name, foreignKey)
			return fmt.Errorf("[constraint] [foreign] violation: '%s' with Id '%s' does not exist", c.foreign.name, foreignKey)
		}
	}

	return nil

}