// tera-serial-line-check temporarily applies and restores CH01 line settings.
package main

import (
	"context"
	"encoding/json"
	"flag"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"
	"time"

	"tera-clone/services/tera-api/internal/serial"
)

const (
	representativeChannel = "CH01"
	representativeDevice  = "/dev/ttyWCH4"
	representativePCPort  = "COM3"
)

type probeClient interface {
	Probe(context.Context, serial.ChannelConfig) (serial.ProbeResult, error)
}

type checkReport struct {
	Kind      string              `json:"kind"`
	Status    string              `json:"status"`
	CheckedAt string              `json:"checked_at"`
	Channel   string              `json:"channel"`
	Device    string              `json:"device"`
	PCPort    string              `json:"pc_port"`
	Requested serial.LineSettings `json:"requested"`
	Probe     *serial.ProbeResult `json:"probe,omitempty"`
	Findings  []string            `json:"findings,omitempty"`
	DataSent  bool                `json:"data_sent"`
}

func main() {
	os.Exit(run(os.Args[1:], os.Stdout, os.Stderr, time.Now))
}

func run(args []string, stdout, stderr io.Writer, now func() time.Time) int {
	flags := flag.NewFlagSet("tera-serial-line-check", flag.ContinueOnError)
	flags.SetOutput(stderr)
	socketPath := flags.String("socket", serial.DefaultSocketPath, "tera-seriald Unix socket")
	baudRate := flags.Int("baud", 115200, "temporary baud rate")
	dataBits := flags.Int("data-bits", 8, "temporary data bits")
	parity := flags.String("parity", "none", "temporary parity")
	stopBits := flags.Int("stop-bits", 1, "temporary stop bits")
	flowControl := flags.String("flow-control", "none", "temporary flow control")
	timeout := flags.Duration("timeout", 10*time.Second, "overall probe timeout")
	if err := flags.Parse(args); err != nil {
		return 2
	}
	if flags.NArg() != 0 || !filepath.IsAbs(*socketPath) || *timeout <= 0 {
		fmt.Fprintln(stderr, "invalid arguments: require an absolute socket path and positive timeout")
		return 2
	}
	requested := serial.ChannelConfig{
		Channel: representativeChannel, BaudRate: *baudRate, DataBits: *dataBits,
		Parity: strings.ToLower(strings.TrimSpace(*parity)), StopBits: *stopBits,
		FlowControl: strings.ToLower(strings.TrimSpace(*flowControl)),
	}
	if _, err := serial.NormalizeLineConfig(serial.LineConfig{
		Device: representativeDevice, BaudRate: requested.BaudRate, DataBits: requested.DataBits,
		Parity: requested.Parity, StopBits: requested.StopBits, FlowControl: requested.FlowControl,
	}); err != nil {
		fmt.Fprintln(stderr, err)
		return 2
	}

	ctx, cancel := context.WithTimeout(context.Background(), *timeout)
	defer cancel()
	report := inspect(ctx, serial.NewSocketClient(*socketPath), requested, now().UTC())
	encoder := json.NewEncoder(stdout)
	encoder.SetIndent("", "  ")
	if err := encoder.Encode(report); err != nil {
		fmt.Fprintln(stderr, "write serial line check report:", err)
		return 1
	}
	if report.Status != "pass" {
		return 1
	}
	return 0
}

func inspect(ctx context.Context, client probeClient, requested serial.ChannelConfig, checkedAt time.Time) checkReport {
	wanted := serial.LineSettings{
		BaudRate: requested.BaudRate, DataBits: requested.DataBits, Parity: requested.Parity,
		StopBits: requested.StopBits, FlowControl: requested.FlowControl,
	}
	report := checkReport{
		Kind: "tera-serial-line-check", Status: "fail", CheckedAt: checkedAt.UTC().Format(time.RFC3339Nano),
		Channel: representativeChannel, Device: representativeDevice, PCPort: representativePCPort,
		Requested: wanted, DataSent: false,
	}
	result, err := client.Probe(ctx, requested)
	if err != nil {
		report.Findings = append(report.Findings, err.Error())
		return report
	}
	report.Probe = &result
	if result.Channel != representativeChannel {
		report.Findings = append(report.Findings, "probe returned a non-representative channel")
	}
	if result.Device != representativeDevice {
		report.Findings = append(report.Findings, "probe returned an unexpected target device")
	}
	if result.Applied != wanted {
		report.Findings = append(report.Findings, "applied readback does not match requested line settings")
	}
	if !result.Restored {
		report.Findings = append(report.Findings, "prior line settings were not restored")
	}
	if len(report.Findings) == 0 {
		report.Status = "pass"
	}
	return report
}