package garmin

import (
	"bufio"
	"encoding/json"
	"io"
	"strings"
	"testing"
)

// wireResponsePayload is what a fake wrapper handler returns for one
// request; the harness fills in the response ID.
type wireResponsePayload struct {
	result json.RawMessage
	err    string
}

func fakeResult(v any) wireResponsePayload {
	b, err := json.Marshal(v)
	if err != nil {
		panic(err)
	}
	return wireResponsePayload{result: b}
}

func fakeError(msg string) wireResponsePayload {
	return wireResponsePayload{err: msg}
}

// newFakeWrapperClient wires a subprocessClient to an in-process goroutine
// that plays the Python wrapper's role, so protocol-level Go logic can be
// tested without python3/garminconnect installed.
func newFakeWrapperClient(t *testing.T, handle func(cmd string, params json.RawMessage) wireResponsePayload) *subprocessClient {
	t.Helper()

	reqR, reqW := io.Pipe()
	respR, respW := io.Pipe()
	t.Cleanup(func() {
		reqW.Close()
		respW.Close()
	})

	go func() {
		scanner := bufio.NewScanner(reqR)
		scanner.Buffer(make([]byte, 0, 64*1024), maxWrapperLineBytes)
		enc := json.NewEncoder(respW)
		for scanner.Scan() {
			var req struct {
				ID     int             `json:"id"`
				Cmd    string          `json:"cmd"`
				Params json.RawMessage `json:"params"`
			}
			if err := json.Unmarshal(scanner.Bytes(), &req); err != nil {
				continue
			}
			payload := handle(req.Cmd, req.Params)
			resp := wireResponse{ID: req.ID, Result: payload.result, Error: payload.err}
			if err := enc.Encode(resp); err != nil {
				return
			}
		}
	}()

	scanner := bufio.NewScanner(respR)
	scanner.Buffer(make([]byte, 0, 64*1024), maxWrapperLineBytes)

	return &subprocessClient{
		started: true,
		enc:     json.NewEncoder(reqW),
		scanner: scanner,
	}
}

func TestSubprocessClient_RoundTrip_DetectsIDMismatch(t *testing.T) {
	reqR, reqW := io.Pipe()
	respR, respW := io.Pipe()
	defer reqW.Close()
	defer respW.Close()

	go func() {
		scanner := bufio.NewScanner(reqR)
		scanner.Buffer(make([]byte, 0, 64*1024), maxWrapperLineBytes)
		scanner.Scan() // read and discard the one request
		json.NewEncoder(respW).Encode(wireResponse{ID: 999, Result: json.RawMessage(`{}`)})
	}()

	scanner := bufio.NewScanner(respR)
	scanner.Buffer(make([]byte, 0, 64*1024), maxWrapperLineBytes)
	c := &subprocessClient{started: true, enc: json.NewEncoder(reqW), scanner: scanner}

	_, err := c.roundTrip("authenticate", nil)
	if err == nil || !strings.Contains(err.Error(), "id mismatch") {
		t.Fatalf("roundTrip error = %v, want an id mismatch error", err)
	}
}

func TestSubprocessClient_RoundTrip_SubprocessClosedIsError(t *testing.T) {
	reqR, reqW := io.Pipe()
	respR, respW := io.Pipe()
	defer reqW.Close()

	go func() {
		scanner := bufio.NewScanner(reqR)
		scanner.Buffer(make([]byte, 0, 64*1024), maxWrapperLineBytes)
		scanner.Scan()
		respW.Close() // subprocess "exited": stdout closes with no response
	}()

	scanner := bufio.NewScanner(respR)
	scanner.Buffer(make([]byte, 0, 64*1024), maxWrapperLineBytes)
	c := &subprocessClient{started: true, enc: json.NewEncoder(reqW), scanner: scanner}

	_, err := c.roundTrip("authenticate", nil)
	if err == nil || !strings.Contains(err.Error(), "closed") {
		t.Fatalf("roundTrip error = %v, want a subprocess-closed error", err)
	}
}

func TestSubprocessClient_RoundTrip_WrapperErrorPropagates(t *testing.T) {
	c := newFakeWrapperClient(t, func(cmd string, params json.RawMessage) wireResponsePayload {
		return fakeError("boom")
	})

	_, err := c.roundTrip("authenticate", nil)
	if err == nil || !strings.Contains(err.Error(), "boom") {
		t.Fatalf("roundTrip error = %v, want it to mention %q", err, "boom")
	}
}

func TestSubprocessClient_UpdateCredentials_ResetsStartedState(t *testing.T) {
	c := &subprocessClient{cfg: Config{GarminEmail: "old@example.com", GarminPassword: "old"}}
	c.started = true // simulate an already-spawned subprocess, no real cmd/pipes

	c.UpdateCredentials("new@example.com", "new")

	if c.cfg.GarminEmail != "new@example.com" || c.cfg.GarminPassword != "new" {
		t.Errorf("cfg after update = %+v, want new@example.com/new", c.cfg)
	}
	if c.started {
		t.Error("started should be reset to false so the next call respawns the subprocess")
	}
}

func TestSubprocessClient_Close_NoOpWhenNotStarted(t *testing.T) {
	c := &subprocessClient{}
	if err := c.Close(); err != nil {
		t.Errorf("Close on an unstarted client = %v, want nil", err)
	}
}