package main

import (
	"bufio"
	"flag"
	"log/slog"
	"os"

	"git.algo.com.cn/public/bloomtool/internal/bloom"
)

const (
	FalseRate = 0.00000001 // 误判率 千万分之一
)

func RunMakeBloom(args ...string) error {
	fs := flag.NewFlagSet("makebloom", flag.ExitOnError)

	txtFile := fs.String("d", "", "device id filename")
	bmpFile := fs.String("b", "", "bitmap filename for output")
	elements := fs.Uint64("e", 0, "max elements. (max 100 0000 0000). if 0 then auto")
	falseRate := fs.Float64("r", FalseRate, "false rate (0.01--0.0000 0000 1)")

	if err := fs.Parse(args); err != nil {
		return err
	} else if fs.NArg() > 0 || *txtFile == "" || *bmpFile == "" ||
		*elements > 10000000000 ||
		*falseRate > 0.01 || *falseRate < 0.000000001 {
		fs.Usage()
		return nil
	}

	return makeBloom(*txtFile, *bmpFile, *elements, *falseRate)
}

func makeBloom(txtFile string, bmpFile string, elements uint64, falseRate float64) error {
	// 打开设备号文件
	slog.Info("open source file", "filename", txtFile)
	tfile, err := os.Open(txtFile)
	if err != nil {
		slog.Error("open source file error", "err", err)
		return err
	}
	defer tfile.Close()

	fstat, err := tfile.Stat()
	if err != nil {
		slog.Error("source file stat error", "err", err)
		return err
	}

	// 计算元素个数，并预留了一些空间。理论上单行md5为32字节，加回车（1个或2个字节）。
	// 这里取30做安全系数。再加10000个保险
	maxElements := uint64(0)
	if elements == 0 {
		maxElements = uint64((fstat.Size() / 30)) + 10000
	} else {
		maxElements = elements
	}

	// 新建布隆过滤器
	bloombmp := bloom.NewWithEstimates(maxElements, falseRate)

	// 逐行读取
	scanner := bufio.NewScanner(tfile)
	lineCount := 1
	for scanner.Scan() {
		if lineCount%100000 == 0 {
			slog.Info("read line", "lineno", lineCount)
		}

		// 转换成bloom bit 写入
		bloombmp.AddString(scanner.Text())

		lineCount++
	}

	// 保存文件
	slog.Info("save bitmap file", "filename", bmpFile)
	err = bloombmp.SaveToFile(bmpFile)

	if err != nil {
		slog.Error("save bitmap file error", "err", err)
		return err
	}

	slog.Info("save bitmap file done")

	return nil
}