//go:build linux

package main

import (
	"context"
	"errors"
	"fmt"
	"io"
	"os"
	"os/signal"
	"strings"
	"time"

	"omnisocketgo/cmd/internal/latencylog"
	peerpkg "omnisocketgo/cmd/internal/peer"
	"omnisocketgo/cmd/internal/protocol"
)

func runPlatform(cfg config, stdout, stderr io.Writer, now func() time.Time) error {
	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt)
	defer stop()

	client, closeLogger, err := dialKCPClient(cfg)
	if err != nil {
		return err
	}
	defer closeLogger()
	defer client.Close()

	if cfg.echo {
		return runEchoMode(ctx, client, stderr)
	}
	return runPingMode(ctx, client, cfg, stdout, stderr, now)
}

func dialKCPClient(cfg config) (*peerpkg.KCPClient, func(), error) {
	options := make([]peerpkg.Option, 0, 3)
	closeLogger := func() {}

	if cfg.latencyLog != "" {
		logger, err := latencylog.NewJSONLLogger(cfg.latencyLog)
		if err != nil {
			return nil, nil, fmt.Errorf("create latency logger %s: %w", cfg.latencyLog, err)
		}
		options = append(options, peerpkg.WithLogger(logger))
		closeLogger = func() {
			_ = logger.Close()
		}
	}
	if cfg.bindIP != "" {
		options = append(options, peerpkg.WithBindIP(cfg.bindIP))
	}
	if cfg.bindDevice != "" {
		options = append(options, peerpkg.WithBindDevice(cfg.bindDevice))
	}

	client, err := peerpkg.DialKCP(cfg.server, cfg.id, options...)
	if err != nil {
		closeLogger()
		return nil, nil, fmt.Errorf("dial kcp server %s: %w", cfg.server, err)
	}
	return client, closeLogger, nil
}

func runPingMode(ctx context.Context, client *peerpkg.KCPClient, cfg config, stdout, stderr io.Writer, now func() time.Time) error {
	if err := writePingHeader(stdout, cfg); err != nil {
		return err
	}

	receiveCh := make(chan protocol.Message, 32)
	receiveErrCh := make(chan error, 1)
	go func() {
		for {
			msg, err := client.Receive()
			if err != nil {
				receiveErrCh <- err
				return
			}
			receiveCh <- msg
		}
	}()

	tracker := newPingTracker(cfg.timeout)
	expiryTicker := time.NewTicker(expiryPollInterval(cfg.timeout))
	defer expiryTicker.Stop()

	var sendTicker *time.Ticker
	if cfg.count == 0 || cfg.count > 1 {
		sendTicker = time.NewTicker(cfg.interval)
		defer sendTicker.Stop()
	}

	nextSeq := uint64(1)
	if err := sendPing(client, tracker, cfg, nextSeq, now); err != nil {
		return err
	}
	nextSeq++

	stopSending := cfg.count == 1
	receiveErrSeen := false

	for {
		if stopSending && tracker.pendingCount() == 0 {
			break
		}

		var sendTick <-chan time.Time
		if !stopSending && sendTicker != nil {
			sendTick = sendTicker.C
		}

		select {
		case <-ctx.Done():
			stopSending = true
		case <-expiryTicker.C:
			for _, seq := range tracker.expire(now()) {
				if err := writeTimeout(stdout, seq); err != nil {
					return err
				}
			}
		case msg := <-receiveCh:
			if err := handlePingMessage(tracker, msg, stdout, stderr, now); err != nil {
				return err
			}
		case err := <-receiveErrCh:
			receiveErrSeen = true
			if ctx.Err() != nil && isExpectedCloseError(err) {
				break
			}
			if stopSending && tracker.pendingCount() == 0 && isExpectedCloseError(err) {
				break
			}
			return fmt.Errorf("receive reply: %w", err)
		case <-sendTick:
			if cfg.count > 0 && tracker.sent >= cfg.count {
				stopSending = true
				continue
			}
			if err := sendPing(client, tracker, cfg, nextSeq, now); err != nil {
				return err
			}
			nextSeq++
			if cfg.count > 0 && tracker.sent >= cfg.count {
				stopSending = true
			}
		}

		if receiveErrSeen && stopSending && tracker.pendingCount() == 0 {
			break
		}
	}

	for _, seq := range tracker.expire(now()) {
		if err := writeTimeout(stdout, seq); err != nil {
			return err
		}
	}
	return writeSummary(stdout, cfg.to, tracker.summary())
}

func sendPing(client *peerpkg.KCPClient, tracker *pingTracker, cfg config, seq uint64, now func() time.Time) error {
	sentAt := now()
	payload, err := buildPingPayload(seq, sentAt.UnixNano(), cfg.size)
	if err != nil {
		return err
	}
	if err := client.SendText(cfg.to, string(payload)); err != nil {
		return fmt.Errorf("send ping seq=%d: %w", seq, err)
	}
	tracker.markSent(seq, sentAt)
	return nil
}

func handlePingMessage(tracker *pingTracker, msg protocol.Message, stdout, stderr io.Writer, now func() time.Time) error {
	switch msg.Type {
	case protocol.MessageTypeText:
		payload, err := parsePingPayload(msg.Body)
		if err != nil {
			_, writeErr := fmt.Fprintf(stderr, "ignore non-ping text message from %s: %v\n", msg.From, err)
			if writeErr != nil {
				return writeErr
			}
			return nil
		}

		result := tracker.observeReply(payload, now())
		switch result.disposition {
		case replyMatched:
			return writeMatchedReply(stdout, payload.Seq, result.rtt)
		case replyDuplicate:
			_, err := fmt.Fprintf(stderr, "seq=%d duplicate or late reply ignored\n", payload.Seq)
			return err
		case replyUnexpected:
			_, err := fmt.Fprintf(stderr, "seq=%d unexpected reply ignored\n", payload.Seq)
			return err
		default:
			return nil
		}
	case protocol.MessageTypeError:
		_, err := fmt.Fprintf(stderr, "server error: %s\n", strings.TrimSpace(string(msg.Body)))
		return err
	default:
		_, err := fmt.Fprintf(stderr, "unexpected message type %s from %s ignored\n", msg.Type, msg.From)
		return err
	}
}

func runEchoMode(ctx context.Context, client *peerpkg.KCPClient, stderr io.Writer) error {
	receiveErrCh := make(chan error, 1)
	go func() {
		receiveErrCh <- client.ReceiveLoop(func(msg protocol.Message) error {
			switch msg.Type {
			case protocol.MessageTypeText:
				return client.SendText(msg.From, string(msg.Body))
			case protocol.MessageTypeError:
				_, err := fmt.Fprintf(stderr, "server error: %s\n", strings.TrimSpace(string(msg.Body)))
				return err
			default:
				_, err := fmt.Fprintf(stderr, "unexpected message type %s from %s ignored\n", msg.Type, msg.From)
				return err
			}
		})
	}()

	select {
	case <-ctx.Done():
		return nil
	case err := <-receiveErrCh:
		if err == nil || (ctx.Err() != nil && isExpectedCloseError(err)) {
			return nil
		}
		return fmt.Errorf("echo receive loop: %w", err)
	}
}

func isExpectedCloseError(err error) bool {
	if err == nil {
		return true
	}
	message := err.Error()
	return errors.Is(err, context.Canceled) ||
		strings.Contains(message, "closed") ||
		strings.Contains(message, "broken pipe") ||
		strings.Contains(message, "io: read/write on closed pipe")
}