// tera-serial-lease-check verifies that CH02-CH48 can acquire and release the
// production tera-seriald stream path. It sends no test payload and never opens
// a raw TTY directly.
package main

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

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

const (
	firstCheckedChannel = 2
	lastCheckedChannel  = 48
)

type leaseController interface {
	Open(context.Context, string) (io.ReadWriteCloser, error)
	Status(context.Context) (serial.StreamSnapshot, error)
}

type channelResult struct {
	Channel      string `json:"channel"`
	Status       string `json:"status"`
	OpenCloseMS  int64  `json:"open_close_ms"`
	ErrorMessage string `json:"error,omitempty"`
}

type report struct {
	Kind              string          `json:"kind"`
	Status            string          `json:"status"`
	GeneratedAt       time.Time       `json:"generated_at"`
	FirstChannel      string          `json:"first_channel"`
	LastChannel       string          `json:"last_channel"`
	ChannelsRequested int             `json:"channels_requested"`
	ChannelsPassed    int             `json:"channels_passed"`
	ChannelsFailed    int             `json:"channels_failed"`
	ActiveLeasesAfter int             `json:"active_leases_after"`
	IdleStatusError   string          `json:"idle_status_error,omitempty"`
	TestPayloadSent   bool            `json:"test_payload_sent"`
	DynamicDeviceScan bool            `json:"dynamic_device_scan"`
	FixedChannelList  bool            `json:"fixed_channel_list"`
	Results           []channelResult `json:"results"`
}

func main() {
	controller := serial.NewStreamSocketClient(serial.DefaultStreamSocketPath, "tera-serial-lease-check")
	os.Exit(run(os.Args[1:], os.Stdout, os.Stderr, controller))
}

func run(args []string, stdout, stderr io.Writer, controller leaseController) int {
	flags := flag.NewFlagSet("tera-serial-lease-check", flag.ContinueOnError)
	flags.SetOutput(stderr)
	perChannelTimeout := flags.Duration("per-channel-timeout", 3*time.Second, "maximum time for one open/close")
	confirmed := flags.Bool("operator-confirmed-ch02-ch48-open-close", false, "confirm a no-test-payload CH02-CH48 open/close check")
	if err := flags.Parse(args); err != nil {
		return 2
	}
	if flags.NArg() != 0 || !*confirmed || *perChannelTimeout <= 0 || *perChannelTimeout > 10*time.Second {
		fmt.Fprintln(stderr, "require explicit CH02-CH48 open/close confirmation and a timeout up to 10s")
		return 2
	}
	if controller == nil {
		fmt.Fprintln(stderr, "serial lease controller is required")
		return 2
	}

	result := report{
		Kind: "tera-serial-lease-check", Status: "pass", GeneratedAt: time.Now().UTC(),
		FirstChannel: "CH02", LastChannel: "CH48",
		ChannelsRequested: lastCheckedChannel - firstCheckedChannel + 1,
		TestPayloadSent:   false, DynamicDeviceScan: false, FixedChannelList: true,
		Results: make([]channelResult, 0, lastCheckedChannel-firstCheckedChannel+1),
	}
	for number := firstCheckedChannel; number <= lastCheckedChannel; number++ {
		channel := fmt.Sprintf("CH%02d", number)
		started := time.Now()
		ctx, cancel := context.WithTimeout(context.Background(), *perChannelTimeout)
		stream, err := controller.Open(ctx, channel)
		if err == nil {
			err = stream.Close()
		}
		cancel()
		entry := channelResult{Channel: channel, Status: "pass", OpenCloseMS: time.Since(started).Milliseconds()}
		if err != nil {
			entry.Status = "fail"
			entry.ErrorMessage = err.Error()
			result.ChannelsFailed++
		} else {
			result.ChannelsPassed++
		}
		result.Results = append(result.Results, entry)
	}

	statusContext, cancelStatus := context.WithTimeout(context.Background(), 3*time.Second)
	status, statusErr := waitForIdle(statusContext, controller)
	cancelStatus()
	result.ActiveLeasesAfter = status.ActiveLeases
	if statusErr != nil {
		result.Status = "fail"
		result.IdleStatusError = statusErr.Error()
		fmt.Fprintln(stderr, statusErr)
	}
	if result.ChannelsFailed != 0 || result.ChannelsPassed != result.ChannelsRequested {
		result.Status = "fail"
	}
	if err := json.NewEncoder(stdout).Encode(result); err != nil {
		fmt.Fprintln(stderr, err)
		return 1
	}
	if result.Status != "pass" {
		return 1
	}
	return 0
}

func waitForIdle(ctx context.Context, controller leaseController) (serial.StreamSnapshot, error) {
	ticker := time.NewTicker(25 * time.Millisecond)
	defer ticker.Stop()
	var latest serial.StreamSnapshot
	for {
		status, err := controller.Status(ctx)
		if err != nil {
			return status, err
		}
		latest = status
		if status.ActiveLeases == 0 {
			return status, nil
		}
		select {
		case <-ctx.Done():
			return latest, fmt.Errorf("serial leases did not return to idle: %w", ctx.Err())
		case <-ticker.C:
		}
	}
}