package main

import (
	"bytes"
	"context"
	"errors"
	"io"
	"log/slog"
	"net"
	"net/http"
	"net/http/httptest"
	"strings"
	"testing"
	"time"
)

func TestHealthEndpointReportsServerIsReady(t *testing.T) {
	server := newProtocolServer("cl3611", cl3611Address, slog.Default())
	request := httptest.NewRequest(http.MethodGet, healthPath, nil)
	response := httptest.NewRecorder()

	server.Handler.ServeHTTP(response, request)

	result := response.Result()
	defer result.Body.Close()
	body, err := io.ReadAll(result.Body)
	if err != nil {
		t.Fatalf("read response body: %v", err)
	}
	if result.StatusCode != http.StatusOK {
		t.Fatalf("status = %d, want %d", result.StatusCode, http.StatusOK)
	}
	if contentType := result.Header.Get("Content-Type"); contentType != "text/plain; charset=utf-8" {
		t.Errorf("Content-Type = %q, want %q", contentType, "text/plain; charset=utf-8")
	}
	if string(body) != "ok\n" {
		t.Errorf("body = %q, want %q", body, "ok\\n")
	}
}

func TestManualEndpointLogsStructuredRequest(t *testing.T) {
	var logs bytes.Buffer
	logger := slog.New(slog.NewTextHandler(&logs, nil))
	server := newProtocolServer("cl3611", cl3611Address, logger)
	request := httptest.NewRequest(http.MethodPost, manualAPIPath, strings.NewReader(`{
		"mode": 1,
		"data": [{"time": 1736305467506000000, "value": 1.25}],
		"target": {
			"type": 1,
			"station": "001",
			"main_pos": "ssu001",
			"sub_pos": "TM1",
			"option": "RMS"
		}
	}`))
	request.RemoteAddr = "127.0.0.1:52130"
	response := httptest.NewRecorder()

	server.Handler.ServeHTTP(response, request)

	if response.Code != http.StatusNoContent {
		t.Fatalf("status = %d, want %d", response.Code, http.StatusNoContent)
	}
	for _, fragment := range []string{
		"protocol=cl3611",
		"listen_port=9001",
		"remote_addr=127.0.0.1:52130",
		"mode=1",
		"target.type=1",
		"target.station=001",
		"target.main_pos=ssu001",
		"target.sub_pos=TM1",
		"target.option=RMS",
		"time=1736305467506000000",
		"value=1.25",
	} {
		if !strings.Contains(logs.String(), fragment) {
			t.Errorf("log %q does not contain %q", logs.String(), fragment)
		}
	}
}

func TestManualEndpointRejectsInvalidJSONAndLogsTheError(t *testing.T) {
	var logs bytes.Buffer
	logger := slog.New(slog.NewTextHandler(&logs, nil))
	server := newProtocolServer("104", protocol104Address, logger)
	request := httptest.NewRequest(http.MethodPost, manualAPIPath, strings.NewReader(`{"mode":`))
	request.RemoteAddr = "127.0.0.1:52131"
	response := httptest.NewRecorder()

	server.Handler.ServeHTTP(response, request)

	if response.Code != http.StatusBadRequest {
		t.Fatalf("status = %d, want %d", response.Code, http.StatusBadRequest)
	}
	for _, fragment := range []string{
		"level=WARN",
		"msg=\"invalid manual sync request\"",
		"protocol=104",
		"listen_port=9002",
		"remote_addr=127.0.0.1:52131",
		"error=",
	} {
		if !strings.Contains(logs.String(), fragment) {
			t.Errorf("log %q does not contain %q", logs.String(), fragment)
		}
	}
}

func TestManualEndpointRejectsOversizedRequest(t *testing.T) {
	server := newProtocolServer("cl3611", cl3611Address, slog.Default())
	body := `{"extra":"` + strings.Repeat("a", maxRequestBody) + `"}`
	request := httptest.NewRequest(http.MethodPost, manualAPIPath, strings.NewReader(body))
	response := httptest.NewRecorder()

	server.Handler.ServeHTTP(response, request)

	if response.Code != http.StatusRequestEntityTooLarge {
		t.Fatalf("status = %d, want %d", response.Code, http.StatusRequestEntityTooLarge)
	}
}

func TestManualEndpointRejectsMultipleJSONDocuments(t *testing.T) {
	server := newProtocolServer("104", protocol104Address, slog.Default())
	request := httptest.NewRequest(http.MethodPost, manualAPIPath, strings.NewReader(`{"mode":1}{"mode":0}`))
	response := httptest.NewRecorder()

	server.Handler.ServeHTTP(response, request)

	if response.Code != http.StatusBadRequest {
		t.Fatalf("status = %d, want %d", response.Code, http.StatusBadRequest)
	}
}

func TestRunClosesFirstListenerWhenSecondListenerFails(t *testing.T) {
	rawListener, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("listen on temporary port: %v", err)
	}
	firstListener := rawListener.(*net.TCPListener)
	listenCalls := 0
	listen := func(_, _ string) (net.Listener, error) {
		listenCalls++
		if listenCalls == 1 {
			return firstListener, nil
		}
		return nil, errors.New("port is already in use")
	}

	err = run(context.Background(), slog.Default(), listen)

	if err == nil || !strings.Contains(err.Error(), protocol104Address) {
		t.Fatalf("run error = %v, want error containing %q", err, protocol104Address)
	}
	if err := firstListener.SetDeadline(time.Now()); err == nil {
		t.Fatal("first listener is still open")
	}
}

func TestRunServesBothProtocolsAndStopsOnCancellation(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	addresses := make(chan string, 2)
	listen := func(_, _ string) (net.Listener, error) {
		listener, err := net.Listen("tcp", "127.0.0.1:0")
		if err == nil {
			addresses <- listener.Addr().String()
		}
		return listener, err
	}
	runErrors := make(chan error, 1)
	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
	go func() {
		runErrors <- run(ctx, logger, listen)
	}()

	cl3611Addr := <-addresses
	protocol104Addr := <-addresses
	waitForHealthyEndpoint(t, cl3611Addr)
	waitForHealthyEndpoint(t, protocol104Addr)
	cancel()

	select {
	case err := <-runErrors:
		if err != nil {
			t.Fatalf("run returned an error during graceful shutdown: %v", err)
		}
	case <-time.After(2 * time.Second):
		t.Fatal("servers did not stop after context cancellation")
	}
}

func TestProtocolServerEnforcesMethodAndPathRouting(t *testing.T) {
	server := newProtocolServer("cl3611", cl3611Address, slog.Default())
	tests := []struct {
		name       string
		method     string
		path       string
		wantStatus int
	}{
		{name: "manual endpoint rejects GET", method: http.MethodGet, path: manualAPIPath, wantStatus: http.StatusMethodNotAllowed},
		{name: "unknown path is not found", method: http.MethodGet, path: "/unknown", wantStatus: http.StatusNotFound},
	}
	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			request := httptest.NewRequest(test.method, test.path, nil)
			response := httptest.NewRecorder()

			server.Handler.ServeHTTP(response, request)

			if response.Code != test.wantStatus {
				t.Fatalf("status = %d, want %d", response.Code, test.wantStatus)
			}
		})
	}
}

func waitForHealthyEndpoint(t *testing.T, address string) {
	t.Helper()
	client := &http.Client{Timeout: 100 * time.Millisecond}
	deadline := time.Now().Add(2 * time.Second)
	for {
		response, err := client.Get("http://" + address + healthPath)
		if err == nil {
			_ = response.Body.Close()
			if response.StatusCode == http.StatusOK {
				return
			}
		}
		if time.Now().After(deadline) {
			t.Fatalf("health endpoint at %s did not become ready", address)
		}
		time.Sleep(10 * time.Millisecond)
	}
}