package textfile

import (
	"os"
	"path/filepath"
	"strings"
	"testing"
	"time"

	"git.mial.net/mokhtar/x1208-exporter/internal/sensor"
)

func sample() sensor.Reading {
	return sensor.Reading{
		ACPresent: true,
		Volts:     4.0625,
		SOC:       97.65625,
		At:        time.Unix(1754661600, 0),
	}
}

// The four original metrics must render exactly as the oneshot exporter did.
// Grafana alerts and the dashboard key on these names and this formatting.
//
// The sample values are exact binary fractions that land on a rounding tie, so
// this also locks the rounding mode: Go rounds half to even, which turns
// 4.0625 into 4.062 and 97.65625 into 97.66.
const goldenHealthy = `# HELP rpi_ups_last_update_seconds Unix timestamp of last successful exporter run.
# TYPE rpi_ups_last_update_seconds gauge
rpi_ups_last_update_seconds 1754661600
# HELP rpi_ups_ac_power AC adapter present (1=plugged in, 0=on battery).
# TYPE rpi_ups_ac_power gauge
rpi_ups_ac_power 1
# HELP rpi_ups_voltage_volts Battery cell voltage from MAX17040 fuel gauge.
# TYPE rpi_ups_voltage_volts gauge
rpi_ups_voltage_volts 4.062
# HELP rpi_ups_battery_percent Battery state of charge from MAX17040 fuel gauge.
# TYPE rpi_ups_battery_percent gauge
rpi_ups_battery_percent 97.66
# HELP rpi_ups_sensor_healthy Whether the most recent UPS read succeeded (1=yes, 0=no).
# TYPE rpi_ups_sensor_healthy gauge
rpi_ups_sensor_healthy 1
# HELP rpi_ups_read_failures_total Cumulative failed UPS reads since exporter start.
# TYPE rpi_ups_read_failures_total counter
rpi_ups_read_failures_total 0
`

func TestRenderGolden(t *testing.T) {
	got := Render(sample(), true, 0)
	if got != goldenHealthy {
		t.Errorf("render mismatch:\n--- got ---\n%s\n--- want ---\n%s", got, goldenHealthy)
	}
}

// A failed read must not advance the timestamp. That frozen value is exactly
// what RpiUpsExporterStale measures.
func TestRenderUnhealthyFreezesTimestamp(t *testing.T) {
	last := sample()
	got := Render(last, false, 3)

	if !strings.Contains(got, "rpi_ups_last_update_seconds 1754661600\n") {
		t.Error("timestamp must stay at the last complete sample")
	}
	if !strings.Contains(got, "rpi_ups_sensor_healthy 0\n") {
		t.Error("unhealthy sample must report rpi_ups_sensor_healthy 0")
	}
	if !strings.Contains(got, "rpi_ups_read_failures_total 3\n") {
		t.Error("failure count must be visible while the sensor is failing")
	}
}

func TestRenderACAbsent(t *testing.T) {
	s := sample()
	s.ACPresent = false
	if !strings.Contains(Render(s, true, 0), "rpi_ups_ac_power 0\n") {
		t.Error("AC absent must render rpi_ups_ac_power 0")
	}
}

func TestWriteAtomicReplacesContent(t *testing.T) {
	dir := t.TempDir()
	path := filepath.Join(dir, "sub", "x1208.prom")

	if err := WriteAtomic(path, "first\n"); err != nil {
		t.Fatalf("first write: %v", err)
	}
	if err := WriteAtomic(path, "second\n"); err != nil {
		t.Fatalf("second write: %v", err)
	}

	got, err := os.ReadFile(path)
	if err != nil {
		t.Fatalf("read back: %v", err)
	}
	if string(got) != "second\n" {
		t.Errorf("content = %q, want %q", got, "second\n")
	}

	info, err := os.Stat(path)
	if err != nil {
		t.Fatalf("stat: %v", err)
	}
	if info.Mode().Perm() != 0o644 {
		t.Errorf("mode = %v, want 0644 (node-exporter must be able to read it)", info.Mode().Perm())
	}
}

// A rename-based write must never leave temporary files behind for the
// collector to trip over.
func TestWriteAtomicLeavesNoTempFiles(t *testing.T) {
	dir := t.TempDir()
	path := filepath.Join(dir, "x1208.prom")
	for i := 0; i < 5; i++ {
		if err := WriteAtomic(path, "x\n"); err != nil {
			t.Fatalf("write %d: %v", i, err)
		}
	}
	entries, err := os.ReadDir(dir)
	if err != nil {
		t.Fatal(err)
	}
	if len(entries) != 1 {
		t.Errorf("directory holds %d entries, want 1", len(entries))
	}
}