package api

import (
	"encoding/json"
	"net/http"
	"net/http/httptest"
	"os"
	"path/filepath"
	"testing"
	"time"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

// writeSession writes one or more JSONL entries to <dir>/sessions/<sessionID>.jsonl.
// The handler scans <brainDir>/sessions/, so test fixtures must mirror that layout.
func writeSession(t *testing.T, dir, sessionID string, entries ...string) {
	t.Helper()
	sessionsDir := filepath.Join(dir, "sessions")
	require.NoError(t, os.MkdirAll(sessionsDir, 0o755))
	path := filepath.Join(sessionsDir, sessionID+".jsonl")
	body := ""
	for _, e := range entries {
		body += e + "\n"
	}
	require.NoError(t, os.WriteFile(path, []byte(body), 0o644))
}

func TestPassRate_HappyPath(t *testing.T) {
	dir := t.TempDir()
	now := time.Now().UTC()
	recent := now.Add(-1 * time.Hour).Format(time.RFC3339)

	writeSession(t, dir, "s1",
		`{"timestamp":"`+recent+`","skill":"tdd","phase":"red","final_status":"pass"}`,
		`{"timestamp":"`+recent+`","skill":"tdd","phase":"green","final_status":"pass"}`,
		`{"timestamp":"`+recent+`","skill":"tdd","phase":"refactor","final_status":"fail"}`,
	)
	writeSession(t, dir, "s2",
		`{"timestamp":"`+recent+`","skill":"code-review","phase":"review","final_status":"pass"}`,
	)

	h := &Handler{brainDir: dir}
	req := httptest.NewRequest(http.MethodGet, "/pass-rate?skill=tdd&window=24h", nil)
	w := httptest.NewRecorder()
	h.PassRate(w, req)

	resp := w.Result()
	require.Equal(t, http.StatusOK, resp.StatusCode)

	var got passRateResponse
	require.NoError(t, json.NewDecoder(resp.Body).Decode(&got))
	assert.Equal(t, "tdd", got.Skill)
	assert.Equal(t, "24h", got.Window)
	assert.Equal(t, 2, got.Pass)
	assert.Equal(t, 1, got.Fail)
	assert.Equal(t, 0, got.Skip)
	assert.Equal(t, 3, got.Total)
	require.NotNil(t, got.PassRate)
	assert.InDelta(t, 0.6667, *got.PassRate, 0.001)
}

func TestPassRate_LegacyVocabulary(t *testing.T) {
	dir := t.TempDir()
	now := time.Now().UTC().Format(time.RFC3339)
	writeSession(t, dir, "s1",
		`{"timestamp":"`+now+`","skill":"tdd","final_status":"ok"}`,
		`{"timestamp":"`+now+`","skill":"tdd","final_status":"error"}`,
		`{"timestamp":"`+now+`","skill":"tdd","final_status":"skipped"}`,
	)

	h := &Handler{brainDir: dir}
	req := httptest.NewRequest(http.MethodGet, "/pass-rate?skill=tdd&window=24h", nil)
	w := httptest.NewRecorder()
	h.PassRate(w, req)

	var got passRateResponse
	require.NoError(t, json.NewDecoder(w.Result().Body).Decode(&got))
	assert.Equal(t, 1, got.Pass, "ok→pass")
	assert.Equal(t, 1, got.Fail, "error→fail")
	assert.Equal(t, 1, got.Skip, "skipped→skip")
}

func TestPassRate_OutsideWindow_Excluded(t *testing.T) {
	dir := t.TempDir()
	old := time.Now().UTC().Add(-30 * 24 * time.Hour).Format(time.RFC3339)
	recent := time.Now().UTC().Add(-1 * time.Hour).Format(time.RFC3339)
	writeSession(t, dir, "s1",
		`{"timestamp":"`+old+`","skill":"tdd","final_status":"pass"}`,
		`{"timestamp":"`+recent+`","skill":"tdd","final_status":"pass"}`,
	)

	h := &Handler{brainDir: dir}
	req := httptest.NewRequest(http.MethodGet, "/pass-rate?skill=tdd&window=24h", nil)
	w := httptest.NewRecorder()
	h.PassRate(w, req)

	var got passRateResponse
	require.NoError(t, json.NewDecoder(w.Result().Body).Decode(&got))
	assert.Equal(t, 1, got.Pass)
	assert.Equal(t, 1, got.Total)
}

func TestPassRate_NoData_ReturnsZerosAndNullRate(t *testing.T) {
	dir := t.TempDir()
	h := &Handler{brainDir: dir}
	req := httptest.NewRequest(http.MethodGet, "/pass-rate?skill=tdd&window=24h", nil)
	w := httptest.NewRecorder()
	h.PassRate(w, req)

	var got passRateResponse
	require.NoError(t, json.NewDecoder(w.Result().Body).Decode(&got))
	assert.Equal(t, 0, got.Pass)
	assert.Equal(t, 0, got.Fail)
	assert.Equal(t, 0, got.Skip)
	assert.Equal(t, 0, got.Total)
	assert.Nil(t, got.PassRate, "pass_rate must be null when pass+fail == 0")
}

func TestPassRate_DefaultsTo7d(t *testing.T) {
	dir := t.TempDir()
	now := time.Now().UTC().Format(time.RFC3339)
	writeSession(t, dir, "s1", `{"timestamp":"`+now+`","skill":"tdd","final_status":"pass"}`)

	h := &Handler{brainDir: dir}
	req := httptest.NewRequest(http.MethodGet, "/pass-rate?skill=tdd", nil) // no window
	w := httptest.NewRecorder()
	h.PassRate(w, req)

	var got passRateResponse
	require.NoError(t, json.NewDecoder(w.Result().Body).Decode(&got))
	assert.Equal(t, "7d", got.Window)
	assert.Equal(t, 1, got.Pass)
}

func TestPassRate_MissingSkill_ReturnsBadRequest(t *testing.T) {
	dir := t.TempDir()
	h := &Handler{brainDir: dir}
	req := httptest.NewRequest(http.MethodGet, "/pass-rate", nil)
	w := httptest.NewRecorder()
	h.PassRate(w, req)
	assert.Equal(t, http.StatusBadRequest, w.Result().StatusCode)
}

func TestPassRate_BadWindow_ReturnsBadRequest(t *testing.T) {
	dir := t.TempDir()
	h := &Handler{brainDir: dir}
	req := httptest.NewRequest(http.MethodGet, "/pass-rate?skill=tdd&window=foo", nil)
	w := httptest.NewRecorder()
	h.PassRate(w, req)
	assert.Equal(t, http.StatusBadRequest, w.Result().StatusCode)
}

func TestPassRate_MalformedLine_Skipped(t *testing.T) {
	dir := t.TempDir()
	now := time.Now().UTC().Format(time.RFC3339)
	writeSession(t, dir, "s1",
		`{"timestamp":"`+now+`","skill":"tdd","final_status":"pass"}`,
		`not valid json`,
		`{"timestamp":"`+now+`","skill":"tdd","final_status":"pass"}`,
	)

	h := &Handler{brainDir: dir}
	req := httptest.NewRequest(http.MethodGet, "/pass-rate?skill=tdd&window=24h", nil)
	w := httptest.NewRecorder()
	h.PassRate(w, req)

	var got passRateResponse
	require.NoError(t, json.NewDecoder(w.Result().Body).Decode(&got))
	assert.Equal(t, 2, got.Pass, "the malformed line is silently skipped")
}