package main

import (
    "bufio"
    "fmt"
    "os"
    "time"
)

// @note This is used to get around bufio.Scanner erroring at large lines
func readln(r *bufio.Reader) (string, error) {
    var (
        isPrefix = true
        err      error
        line, ln []byte
    )

    for isPrefix && err == nil {
        line, isPrefix, err = r.ReadLine()
        ln = append(ln, line...)
    }

    return string(ln), err
}

func reader(filePath string) {
    f, err := os.Open(filePath)
    if err != nil {
        panic(err)
    }

    reader := bufio.NewReader(f)
    fmt.Print("READER >> created\n")

    line, readErr := readln(reader)

    for readErr == nil {
        fmt.Printf("READER >> read 1 line: %+v\n", line)
        line, readErr = readln(reader)
    }

    fmt.Printf("READER >> read finished: %+v\n", readErr)
}

func writer(filePath string) {
    f, err := os.OpenFile(filePath, os.O_WRONLY, 0600)

    fmt.Printf("WRITER << opened: %+v|%+v\n", f, err)
    if err != nil {
        panic(err)
    }

    fmt.Printf("WRITER << encoder created\n")

    for i := 0; i < 3; i++ {
        time.Sleep(1 * time.Second)
        _, err = f.WriteString(fmt.Sprint("line", i, "\n"))
        fmt.Printf("WRITER << written line%d, %+v\n", i, err)
    }

    time.Sleep(1 * time.Second)
    err = f.Close()
    fmt.Printf("WRITER << closed: %+v\n", err)
}

func main() {
    fifo := os.Args[1]

    fmt.Printf("STARTED %s\n", fifo)

    go writer(fifo)
    reader(fifo)

    fmt.Print("ALL DONE\n")
}