package main

import (
	"bytes"
	"log"
	"strings"
	"testing"
)

// F-OBS (Campaign 8): on a default `info`-level box there was NO positive observable that
// `deadapp-check` had run. Its per-cycle scheduler line goes through Scheduler.dbg(), which is gated
// on logging.level==debug and therefore never PRODUCED on a default box — so it could not even reach
// the always-DEBUG ring — and a 30 s interval also puts the job on the scheduler's quiet path.
//
// "No alarms" was therefore indistinguishable from "the detector never ran", which is exactly the
// fallacy this project now has a standing rule against, and it undermines confidence in the
// F-CRIT-1 fix in the field.
//
// Scenario F — the observable must appear AT INFO LEVEL. These tests assert the emitted LINE, not
// merely that a function was called; asserting the call would reproduce the original mistake.

// RED-PROOF: delete the logger.Printf in noteDeadAppScan (or drop the whole call from the job
// closure) → every case below sees an empty buffer and this fails with
// "no observable emitted at scan 20 — silence is indistinguishable from not running".
func TestNoteDeadAppScan_EmitsAtInfoLevel(t *testing.T) {
	var buf bytes.Buffer
	lg := log.New(&buf, "", 0)

	noteDeadAppScan(lg, deadAppHeartbeatEvery, 7, 2)

	out := buf.String()
	if out == "" {
		t.Fatalf("no observable emitted at scan %d — silence is indistinguishable from not running", deadAppHeartbeatEvery)
	}
	if !strings.Contains(out, "[INFO]") {
		t.Errorf("the observable is not at INFO level, so a default `logging.level: info` box would never see it:\n%s", out)
	}
	if !strings.Contains(out, "[deadapp]") {
		t.Errorf("the observable does not identify the check that produced it:\n%s", out)
	}
	// it must carry WHAT IT SAW, not just "I ran" — an operator needs to distinguish
	// "running and everything is up" from "running and 2 apps are down".
	for _, want := range []string{"scans since boot", "evaluated", "currently down"} {
		if !strings.Contains(out, want) {
			t.Errorf("the observable omits %q — it proves the check ran but not what it found:\n%s", want, out)
		}
	}
}

// It must NOT be a line per run. At a 30 s cadence that is 2880 lines/day, which is precisely why
// the original author chose silence — so a fix that floods is not a fix.
//
// RED-PROOF: change the guard to `scans%1 != 0` (i.e. emit every run) → this fails with
// "emitted 60 lines across 60 scans — that is the flood that made silence attractive".
func TestNoteDeadAppScan_IsASummaryNotAFlood(t *testing.T) {
	var buf bytes.Buffer
	lg := log.New(&buf, "", 0)

	const scans = 60
	for i := 1; i <= scans; i++ {
		noteDeadAppScan(lg, i, 3, 0)
	}

	got := strings.Count(buf.String(), "[deadapp] check alive")
	want := scans / deadAppHeartbeatEvery
	if got == scans {
		t.Fatalf("emitted %d lines across %d scans — that is the flood that made silence attractive", got, scans)
	}
	if got != want {
		t.Errorf("emitted %d heartbeat lines across %d scans, want %d (one per %d)", got, scans, want, deadAppHeartbeatEvery)
	}
}

// The cadence must be frequent enough that a STALLED detector is obvious well inside the 180 s alarm
// grace this check feeds. 20 scans x 30 s = 10 min; if someone widens it to hours the observable
// stops being useful as a liveness signal, and this is the tripwire.
func TestDeadAppHeartbeatEvery_StaysUsefulAsALivenessSignal(t *testing.T) {
	const scanInterval = 30 // seconds, matching sched.Every("deadapp-check", 30*time.Second, ...)
	periodSec := deadAppHeartbeatEvery * scanInterval
	if periodSec > 15*60 {
		t.Errorf("heartbeat period is %ds (>15min) — too sparse to notice a stalled detector", periodSec)
	}
	if deadAppHeartbeatEvery < 2 {
		t.Errorf("heartbeat every %d scans is a per-run flood", deadAppHeartbeatEvery)
	}
}

// Off-cadence scans stay quiet, and a nil logger is tolerated (the job closure must never panic).
func TestNoteDeadAppScan_QuietOffCadenceAndNilSafe(t *testing.T) {
	var buf bytes.Buffer
	lg := log.New(&buf, "", 0)
	noteDeadAppScan(lg, deadAppHeartbeatEvery-1, 1, 0)
	if buf.Len() != 0 {
		t.Errorf("emitted off-cadence:\n%s", buf.String())
	}
	noteDeadAppScan(nil, deadAppHeartbeatEvery, 1, 0) // must not panic
}