package main

import (
	"bufio"
	"bytes"
	"context"
	"fmt"
	"io"
	"log"
	"os"
	"time"

	"github.com/briandowns/spinner"
	"github.com/schollz/progressbar/v3"
)

func RunBackfiller(cfg WorkerConfiguration, workerFunc GenericWorker) {
	ctx := context.Background()
	wp := NewWorkpool(ctx, cfg, workerFunc)

	b := Backfiller{
		Filename: cfg.Filename,
		Workpool: wp,
	}
	err := b.Run()
	if err != nil {
		fmt.Println(err)
	}

	fmt.Println("done backfiller!")
}

type Backfiller struct {
	Filename string
	Strategy string
	Workpool *Workpool
}

func (b *Backfiller) Run() error {
	f, err := os.Open(b.Filename)
	if err != nil {
		return err
	}

	s := spinner.New(spinner.CharSets[14], 100*time.Millisecond)
	s.Color("red")
	s.Suffix = fmt.Sprintf(" counting lines")

	s.Start()
	pLines, err := b.countLines()
	if err != nil {
		return err
	}
	s.Stop()

	fmt.Printf("lines: %d \n ", pLines)

	b.Workpool.Bar = progressbar.Default(int64(pLines))

	counter := 0
	defer f.Close()

	r := bufio.NewReader(f)

	// read file line by line and send to workpool
	for {
		line, _, err := r.ReadLine() //loading chunk into buffer
		if err != nil {
			if err == io.EOF {
				break
			}
			log.Fatalf("a real error happened here: %v\n", err)
		}
		b.Workpool.Queue <- string(line)
		counter += 1
	}

	// send exit signal to all workers
	for i := 0; i < b.Workpool.Workers; i++ {
		b.Workpool.Queue <- "exit"
	}

	// wait for all workers to finish
	b.Workpool.WG.Wait()

	fmt.Printf("processed %d lines\n", counter)

	return nil
}

func (b *Backfiller) countLines() (int, error) {
	file, _ := os.Open(b.Filename)
	defer file.Close()

	buf := make([]byte, 32*1024)
	count := 0
	lineSep := []byte{'\n'}

	for {
		c, err := file.Read(buf)
		count += bytes.Count(buf[:c], lineSep)

		switch {
		case err == io.EOF:
			return count, nil

		case err != nil:
			return count, err
		}
	}

}