package main

import (
	"bytes"
	"net/http"
	"net/http/httptest"
	"os"
	"strings"
	"testing"
	"time"
)

func TestHandleIndexRendersWatts(t *testing.T) {
	srv := &server{secret: "secret", store: &store{value: 123, updatedAt: time.Date(2026, 4, 20, 12, 34, 56, 0, time.UTC)}}
	req := httptest.NewRequest(http.MethodGet, "/", nil)
	rec := httptest.NewRecorder()

	srv.handleIndex(rec, req)

	if rec.Code != http.StatusOK {
		t.Fatalf("status = %d, want %d", rec.Code, http.StatusOK)
	}
	if !strings.Contains(rec.Body.String(), "123") {
		t.Fatalf("response did not contain watt value: %s", rec.Body.String())
	}
	if !strings.Contains(rec.Body.String(), "Last updated:") {
		t.Fatalf("response did not contain last updated label: %s", rec.Body.String())
	}
	if !strings.Contains(rec.Body.String(), "20.04.2026 12:34:56") {
		t.Fatalf("response did not contain german datetime: %s", rec.Body.String())
	}
}

func TestHandleWriteRequiresSecret(t *testing.T) {
	srv := &server{secret: "secret", store: &store{}}
	req := httptest.NewRequest(http.MethodPost, "/write", bytes.NewBufferString(`{"watts":456}`))
	req.Header.Set("Content-Type", "application/json")
	rec := httptest.NewRecorder()

	srv.handleWrite(rec, req)

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

func TestHandleWriteStoresValue(t *testing.T) {
	srv := &server{secret: "secret", store: &store{}}
	req := httptest.NewRequest(http.MethodPost, "/write", bytes.NewBufferString(`{"watts":456}`))
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("X-Secret", "secret")
	rec := httptest.NewRecorder()

	srv.handleWrite(rec, req)

	if rec.Code != http.StatusOK {
		t.Fatalf("status = %d, want %d", rec.Code, http.StatusOK)
	}
	if got := srv.store.get(); got != 456 {
		t.Fatalf("stored watts = %d, want %d", got, 456)
	}
	if srv.store.updatedAt.IsZero() {
		t.Fatal("updatedAt was not set")
	}
}

func TestLoadConfig(t *testing.T) {
	path := t.TempDir() + "/config.json"
	if err := os.WriteFile(path, []byte(`{"write_secret":"secret","addr":":9090","chart_max_watts":750}`), 0o600); err != nil {
		t.Fatalf("write config: %v", err)
	}

	cfg, err := loadConfig(path)
	if err != nil {
		t.Fatalf("loadConfig returned error: %v", err)
	}
	if cfg.WriteSecret != "secret" {
		t.Fatalf("write_secret = %q, want %q", cfg.WriteSecret, "secret")
	}
	if cfg.Addr != ":9090" {
		t.Fatalf("addr = %q, want %q", cfg.Addr, ":9090")
	}
	if cfg.ChartMaxWatts != 750 {
		t.Fatalf("chart_max_watts = %d, want %d", cfg.ChartMaxWatts, 750)
	}
}

func TestBuildHistoryChartEmpty(t *testing.T) {
	chart := buildHistoryChart(nil, 0)
	if !strings.Contains(string(chart), "No power history yet") {
		t.Fatalf("empty chart did not contain fallback text: %s", string(chart))
	}
}

func TestBuildHistoryChartRendersPolyline(t *testing.T) {
	history := []sample{
		{at: time.Date(2026, 4, 20, 0, 0, 0, 0, time.UTC), value: 100},
		{at: time.Date(2026, 4, 20, 6, 0, 0, 0, time.UTC), value: 200},
		{at: time.Date(2026, 4, 20, 12, 0, 0, 0, time.UTC), value: 150},
	}

	chart := buildHistoryChart(history, 0)
	if !strings.Contains(string(chart), "<polyline") {
		t.Fatalf("chart did not contain polyline: %s", string(chart))
	}
	for _, want := range []string{"W", "00:00", "06:00", "12:00"} {
		if !strings.Contains(string(chart), want) {
			t.Fatalf("chart did not include %q: %s", want, string(chart))
		}
	}
	if !strings.Contains(string(chart), "0 W") {
		t.Fatalf("chart did not include zero baseline: %s", string(chart))
	}
}

func TestBuildHistoryChartUsesConfiguredMax(t *testing.T) {
	history := []sample{{at: time.Date(2026, 4, 20, 12, 0, 0, 0, time.UTC), value: 250}}
	chart := buildHistoryChart(history, 1000)
	if !strings.Contains(string(chart), "1000 W") {
		t.Fatalf("chart did not include configured max: %s", string(chart))
	}
	if strings.Contains(string(chart), "250 W") {
		t.Fatalf("chart unexpectedly used sample max instead of configured max: %s", string(chart))
	}
}

func TestStoreTrimsHistoryToMaxPoints(t *testing.T) {
	s := &store{}
	base := time.Date(2026, 4, 20, 0, 0, 0, 0, time.UTC)
	s.mu.Lock()
	for i := 0; i < maxHistoryPoints+25; i++ {
		s.history = append(s.history, sample{at: base.Add(time.Duration(i) * time.Second), value: i})
	}
	s.trimHistoryLocked(base.Add(time.Duration(maxHistoryPoints+25) * time.Second))
	got := len(s.history)
	s.mu.Unlock()

	if got != maxHistoryPoints {
		t.Fatalf("history length = %d, want %d", got, maxHistoryPoints)
	}
	if s.history[0].value != 25 {
		t.Fatalf("oldest retained value = %d, want %d", s.history[0].value, 25)
	}
}