// errors_test.go — errors.go 3 個純 helper（WriteError / WriteSuccess / WriteNotImplemented）的 unit test。
//
// Owner: testing agent（補測任務 — internal/api 弱處純函式）
//
// 這 3 個函式直接寫 gin.Context 的 JSON response（envelope 形狀對齊 api-spec.md §11）。
// 用 httptest.NewRecorder() + gin.CreateTestContext 驅動，驗 status code + envelope 結構 +
// request_id 帶入 + details / nil 邊界。
//
// 注意：errors_db.go 的 DB 錯誤映射另由 errors_db_test.go 覆蓋，本檔不重複。
package api

import (
	"encoding/json"
	"net/http"
	"net/http/httptest"
	"testing"

	"github.com/gin-gonic/gin"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

// newTestCtx 建立一個帶 ResponseRecorder 的 gin.Context；reqID 非空時塞入 request_id。
func newTestCtx(reqID string) (*gin.Context, *httptest.ResponseRecorder) {
	w := httptest.NewRecorder()
	c, _ := gin.CreateTestContext(w)
	if reqID != "" {
		c.Set(ctxKeyRequestID, reqID)
	}
	return c, w
}

// decodeErrorBody 把 recorder body 解成 ErrorBody。
func decodeErrorBody(t *testing.T, w *httptest.ResponseRecorder) ErrorBody {
	t.Helper()
	var body ErrorBody
	require.NoError(t, json.Unmarshal(w.Body.Bytes(), &body))
	return body
}

// ───────────────────────── WriteError ─────────────────────────

// happy：寫一個帶 request_id 的 404 錯誤，envelope 形狀正確。
func TestWriteError_Happy_WithRequestID(t *testing.T) {
	c, w := newTestCtx("req-123")
	WriteError(c, http.StatusNotFound, ErrCodeNotFound, "device not found", nil)

	assert.Equal(t, http.StatusNotFound, w.Code)
	assert.Equal(t, "application/json; charset=utf-8", w.Header().Get("Content-Type"))

	body := decodeErrorBody(t, w)
	assert.False(t, body.Success, "錯誤 envelope success 必為 false")
	require.NotNil(t, body.Error)
	assert.Equal(t, ErrCodeNotFound, body.Error.Code)
	assert.Equal(t, "device not found", body.Error.Message)
	assert.Equal(t, "req-123", body.Error.RequestID, "WriteError 應自動帶上 request_id")
	assert.Nil(t, body.Error.Details, "未傳 details 時應為 nil（omitempty）")
}

// boundary：帶 details（validation 細節）時，details 應出現在 envelope。
func TestWriteError_WithDetails(t *testing.T) {
	c, w := newTestCtx("req-val")
	details := []FieldError{
		{Field: "name", Message: "required"},
		{Field: "target_chip", Message: "unsupported"},
	}
	WriteError(c, http.StatusBadRequest, ErrCodeValidationFailed, "validation failed", details)

	assert.Equal(t, http.StatusBadRequest, w.Code)
	body := decodeErrorBody(t, w)
	require.NotNil(t, body.Error)
	require.Len(t, body.Error.Details, 2)
	assert.Equal(t, "name", body.Error.Details[0].Field)
	assert.Equal(t, "required", body.Error.Details[0].Message)
	assert.Equal(t, "target_chip", body.Error.Details[1].Field)
}

// empty / edge：沒有 request_id 時，request_id 欄位被 omitempty 省略（不應出現空字串 key 影響 client）。
func TestWriteError_NoRequestID_OmitsField(t *testing.T) {
	c, w := newTestCtx("") // 不塞 request_id
	WriteError(c, http.StatusInternalServerError, ErrCodeInternalError, "boom", nil)

	assert.Equal(t, http.StatusInternalServerError, w.Code)

	// request_id 為 omitempty，空值時不應出現在 JSON
	raw := w.Body.String()
	assert.NotContains(t, raw, "request_id", "request_id 為空時應被 omitempty 省略")

	body := decodeErrorBody(t, w)
	require.NotNil(t, body.Error)
	assert.Equal(t, ErrCodeInternalError, body.Error.Code)
	assert.Empty(t, body.Error.RequestID)
}

// edge：空 details slice（len 0）→ omitempty 省略（不應出現 "details": []）。
func TestWriteError_EmptyDetailsSlice_Omitted(t *testing.T) {
	c, w := newTestCtx("req-x")
	WriteError(c, http.StatusBadRequest, ErrCodeValidationFailed, "msg", []FieldError{})

	raw := w.Body.String()
	assert.NotContains(t, raw, "details", "空 details slice 應被 omitempty 省略")
}

// ───────────────────────── WriteSuccess ─────────────────────────

// happy：寫一個 200 成功回應，data 帶入。
func TestWriteSuccess_Happy(t *testing.T) {
	c, w := newTestCtx("")
	payload := map[string]any{"id": "m-1", "name": "yolo"}
	WriteSuccess(c, http.StatusOK, payload)

	assert.Equal(t, http.StatusOK, w.Code)

	var body SuccessBody
	require.NoError(t, json.Unmarshal(w.Body.Bytes(), &body))
	assert.True(t, body.Success, "成功 envelope success 必為 true")

	data, ok := body.Data.(map[string]any)
	require.True(t, ok)
	assert.Equal(t, "m-1", data["id"])
	assert.Equal(t, "yolo", data["name"])
}

// edge：data 為 nil（如 201 Created 無 body）→ data 被 omitempty 省略，但 success 仍在。
func TestWriteSuccess_NilData_OmitsData(t *testing.T) {
	c, w := newTestCtx("")
	WriteSuccess(c, http.StatusCreated, nil)

	assert.Equal(t, http.StatusCreated, w.Code)
	raw := w.Body.String()
	assert.Contains(t, raw, `"success":true`)
	assert.NotContains(t, raw, "data", "nil data 應被 omitempty 省略")
}

// boundary：non-201 status 也能用（WriteSuccess 不限定 status）。
func TestWriteSuccess_CustomStatus(t *testing.T) {
	c, w := newTestCtx("")
	WriteSuccess(c, http.StatusAccepted, map[string]string{"state": "queued"})

	assert.Equal(t, http.StatusAccepted, w.Code)
	var body SuccessBody
	require.NoError(t, json.Unmarshal(w.Body.Bytes(), &body))
	assert.True(t, body.Success)
}

// ───────────────────────── WriteNotImplemented ─────────────────────────

// happy：回 501 NOT_IMPLEMENTED，hint 帶進 message。
func TestWriteNotImplemented_Happy(t *testing.T) {
	c, w := newTestCtx("req-ni")
	WriteNotImplemented(c, "clusters endpoint pending B5")

	assert.Equal(t, http.StatusNotImplemented, w.Code)
	body := decodeErrorBody(t, w)
	require.NotNil(t, body.Error)
	assert.False(t, body.Success)
	assert.Equal(t, ErrCodeNotImplemented, body.Error.Code)
	assert.Equal(t, "clusters endpoint pending B5", body.Error.Message)
	assert.Equal(t, "req-ni", body.Error.RequestID)
}

// edge：空 hint 也成立（message 為空字串、code 仍為 NOT_IMPLEMENTED）。
func TestWriteNotImplemented_EmptyHint(t *testing.T) {
	c, w := newTestCtx("")
	WriteNotImplemented(c, "")

	assert.Equal(t, http.StatusNotImplemented, w.Code)
	body := decodeErrorBody(t, w)
	require.NotNil(t, body.Error)
	assert.Equal(t, ErrCodeNotImplemented, body.Error.Code)
	assert.Empty(t, body.Error.Message)
}