// SPDX-License-Identifier: MIT
package main

import (
	"bufio"
	"fmt"
	"os"
	"os/signal"
	"syscall"

	"github.com/alexjch/go-dmesg/pkg/dmesg"
	"github.com/gokrazy/gokrazy"
)

// Primitives are:
//   - scanner, a bufio.Scanner that reads from /dev/kmsg
//   - decoder, a dmesg.Decoder that wraps a scanner and decodes log records
//     {decoder{scanner}}}
var LEVELS = map[uint8]string{
	0: "Emergency",
	1: "Alert",
	2: "Critical",
	3: "Error",
	4: "Warning",
	5: "Notice",
	6: "Info",
	7: "Debug",
}

func NewScanner() (*dmesg.Scanner, error) {
	// Open /dev/kmsg for reading in a non-blocking manner
	f, err := os.OpenFile("/dev/kmsg", syscall.O_RDONLY|syscall.O_NONBLOCK, 0)
	if err != nil {
		return nil, fmt.Errorf("Failed to open kernel log: %w", err)
	}
	f.Seek(0, 3)
	// Wrap an os.File in a bufio.Scanner
	scanner := bufio.NewScanner(f)
	return &dmesg.Scanner{
		Scanner:    *scanner,
		ReadCloser: f,
	}, nil
}
func main() {
	gokrazy.WaitForClock()
	// Handle Ctrl-C
	c := make(chan os.Signal, 1)
	signal.Notify(c, os.Interrupt)
	// Create a scanner
	scan, err := NewScanner()
	if err != nil {
		panic(err)
	}
	defer scan.Close()
	// Create a decoder
	dec, err := dmesg.NewDecoder(scan)
	if err != nil {
		panic(err)
	}
	// Stop the decoder when Ctrl-C is pressed
	go func() {
		<-c
		dec.Stop()
	}()
	// Follow the decoder until Ctrl-C is pressed
	if err := dec.Follow(func(r *dmesg.Record) {
		fmt.Printf("%9s: %v: %s\n", LEVELS[r.Priority], r.Timestamp, r.Message)
	}); err != nil {
		panic(err)
	}
}