package main

import (
	"encoding/json"
	"os"
	"path/filepath"
	"testing"
	"time"
)

func TestRunMergeComputesArrivalAndPersistenceGate(t *testing.T) {
	dir := t.TempDir()
	a := AgentSummary{RunID: "run1", Scenario: "p2p", Machine: "a", ReadyConnections: 1000,
		ExpectedConnections: 1000,
		PublishAttempted:    10, PublishAccepted: 10, ExpectedPeer: 10, ReceivedPeer: 9,
		RealtimeLost: 1, HistoryChecked: 10, HistoryFound: 10}
	b := AgentSummary{RunID: "run1", Scenario: "p2p", Machine: "b", ReadyConnections: 1000,
		ExpectedConnections: 1000,
		PublishAttempted:    10, PublishAccepted: 10, ExpectedPeer: 10, ReceivedPeer: 10,
		HistoryChecked: 10, HistoryFound: 9, PersistenceLost: 1, OutOfOrder: 1,
		OrderingViolations: []OrderingViolation{{ReceiverMachine: "b", ReceiverIndex: 7, PreviousSeq: 12, CurrentSeq: 11}}}
	aPath, bPath, reportPath := filepath.Join(dir, "a.json"), filepath.Join(dir, "b.json"), filepath.Join(dir, "report.json")
	writeSummaryForTest(t, aPath, a)
	writeSummaryForTest(t, bPath, b)
	if err := runMerge(aPath, bPath, reportPath); err != nil {
		t.Fatal(err)
	}
	var report CombinedReport
	raw, err := os.ReadFile(reportPath)
	if err != nil {
		t.Fatal(err)
	}
	if err = json.Unmarshal(raw, &report); err != nil {
		t.Fatal(err)
	}
	if report.ExpectedDeliveries != 20 || report.ReceivedDeliveries != 19 || report.ArrivalRate != 0.95 || report.LossRate != 0.05 {
		t.Fatalf("unexpected delivery totals: %+v", report)
	}
	if report.Passed || report.PersistenceLost != 1 {
		t.Fatalf("correctness gate did not fail: %+v", report)
	}
	if len(report.OrderingViolations) != 1 || report.OrderingViolations[0].ReceiverIndex != 7 {
		t.Fatalf("ordering violations were not merged: %+v", report.OrderingViolations)
	}
}

func TestMergedHistogramP95(t *testing.T) {
	agents := []AgentSummary{
		{AckLatency: HistogramSnapshot{Count: 10, MaxMS: 900, Buckets: map[string]int64{"200ms": 9, "1s": 1}}},
		{AckLatency: HistogramSnapshot{Count: 10, MaxMS: 300, Buckets: map[string]int64{"200ms": 10}}},
	}
	if got := mergedHistogramP95(agents, func(summary AgentSummary) HistogramSnapshot { return summary.AckLatency }); got != 200 {
		t.Fatalf("p95=%v", got)
	}
}

func TestMergedAckP95UsesExactAcceptedTimestamps(t *testing.T) {
	base := time.Date(2026, 9, 27, 8, 0, 0, 0, time.UTC)
	agents := []AgentSummary{{
		AckLatency: HistogramSnapshot{Count: 4, MaxMS: 900, Buckets: map[string]int64{"1s": 4}},
		AcceptedLocal: []AcceptedMessage{
			{SentAt: base, AckAt: base.Add(100 * time.Millisecond)},
			{SentAt: base, AckAt: base.Add(200 * time.Millisecond)},
			{SentAt: base, AckAt: base.Add(300 * time.Millisecond)},
			{SentAt: base, AckAt: base.Add(400 * time.Millisecond)},
		},
	}}
	if got := mergedAckP95(agents); got != 400 {
		t.Fatalf("exact p95=%v want=400", got)
	}
}

func TestMergedAckP95FallsBackWhenRawSamplesAreIncomplete(t *testing.T) {
	agents := []AgentSummary{{
		AckLatency:    HistogramSnapshot{Count: 2, MaxMS: 900, Buckets: map[string]int64{"1s": 2}},
		AcceptedLocal: []AcceptedMessage{{SentAt: time.Now(), AckAt: time.Now().Add(100 * time.Millisecond)}},
	}}
	if got := mergedAckP95(agents); got != 1000 {
		t.Fatalf("fallback p95=%v want=1000", got)
	}
}

func writeSummaryForTest(t *testing.T, path string, summary AgentSummary) {
	t.Helper()
	raw, err := json.Marshal(summary)
	if err != nil {
		t.Fatal(err)
	}
	if err = os.WriteFile(path, raw, 0o600); err != nil {
		t.Fatal(err)
	}
}