package indexparamcheck

import (
	"fmt"
	"strconv"
)

// ivfPQChecker checks if a IVF_PQ index can be built.
type ivfPQChecker struct {
	ivfBaseChecker
}

// CheckTrain checks if ivf-pq index can be built with the specific index parameters.
func (c *ivfPQChecker) CheckTrain(params map[string]string) error {
	if err := c.ivfBaseChecker.CheckTrain(params); err != nil {
		return err
	}

	return c.checkPQParams(params)
}

func (c *ivfPQChecker) checkPQParams(params map[string]string) error {
	dimStr, dimensionExist := params[DIM]
	if !dimensionExist {
		return fmt.Errorf("dimension not found")
	}

	dimension, err := strconv.Atoi(dimStr)
	if err != nil { // invalid dimension
		return fmt.Errorf("invalid dimension: %s", dimStr)
	}

	// nbits can be set to default: 8
	nbitsStr, nbitsExist := params[NBITS]
	if nbitsExist {
		nbits, err := strconv.Atoi(nbitsStr)
		if err != nil { // invalid nbits
			return fmt.Errorf("invalid nbits: %s", nbitsStr)
		}

		if nbits < 1 || nbits > 64 {
			return fmt.Errorf("parameter `nbits` out of range, expect range [1,64], current value: %d", nbits)
		}
	}

	mStr, ok := params[IVFM]
	if !ok {
		return fmt.Errorf("parameter `m` not found")
	}
	m, err := strconv.Atoi(mStr)
	if err != nil || m == 0 { // invalid m
		return fmt.Errorf("invalid `m`: %s", mStr)
	}

	return c.checkCPUPQParams(dimension, m)
}

func (c *ivfPQChecker) checkCPUPQParams(dimension, m int) error {
	if (dimension % m) != 0 {
		return fmt.Errorf("dimension must be able to be divided by `m`, dimension: %d, m: %d", dimension, m)
	}
	return nil
}

func newIVFPQChecker() IndexChecker {
	return &ivfPQChecker{}
}