package store

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

func auditFixture(t *testing.T) string {
	t.Helper()
	return filepath.Join(t.TempDir(), "audit.jsonl")
}

func sampleSummary(id string) SessionSummary {
	return SessionSummary{
		SessionID:   id,
		NextAction:  "write plan",
		SuccessCond: "plan committed",
		Outcome:     "completed",
		StartedUnix: 1000,
		EndedUnix:   2000,
		SwitchCount: 3,
		Buckets: []BucketTotal{
			{Class: "code", Title: "antidrift", Seconds: 540},
			{Class: "firefox", Title: "docs", Seconds: 120},
		},
	}
}

func TestAppendSessionChainsAndVerifies(t *testing.T) {
	path := auditFixture(t)
	for i := 0; i < 3; i++ {
		if err := AppendSession(path, sampleSummary("session-"+string(rune('a'+i)))); err != nil {
			t.Fatalf("append %d: %v", i, err)
		}
	}
	if err := VerifyChain(path); err != nil {
		t.Fatalf("chain should verify: %v", err)
	}
}

func TestGenesisPrevHashIsZeros(t *testing.T) {
	path := auditFixture(t)
	if err := AppendSession(path, sampleSummary("session-a")); err != nil {
		t.Fatalf("append: %v", err)
	}
	data, _ := os.ReadFile(path)
	if !strings.Contains(string(data), strings.Repeat("0", 64)) {
		t.Fatalf("genesis prev_hash should be 64 zeros, got: %s", data)
	}
}

func TestVerifyEmptyChain(t *testing.T) {
	if err := VerifyChain(auditFixture(t)); err != nil {
		t.Fatalf("empty/missing chain should verify, got %v", err)
	}
}

func TestTamperDetected(t *testing.T) {
	path := auditFixture(t)
	_ = AppendSession(path, sampleSummary("session-a"))
	_ = AppendSession(path, sampleSummary("session-b"))
	_ = AppendSession(path, sampleSummary("session-c"))

	// Corrupt the middle line's switch_count.
	data, _ := os.ReadFile(path)
	lines := strings.Split(strings.TrimRight(string(data), "\n"), "\n")
	lines[1] = strings.Replace(lines[1], `"switch_count":3`, `"switch_count":99`, 1)
	if err := os.WriteFile(path, []byte(strings.Join(lines, "\n")+"\n"), 0o644); err != nil {
		t.Fatalf("rewrite: %v", err)
	}
	err := VerifyChain(path)
	if err == nil || !strings.Contains(err.Error(), "line 2") {
		t.Fatalf("tamper on line 2 should be reported, got %v", err)
	}
}

func TestRecentSessionsReturnsLastNOldestFirst(t *testing.T) {
	path := auditFixture(t)
	for _, id := range []string{"a", "b", "c"} {
		if err := AppendSession(path, sampleSummary("session-"+id)); err != nil {
			t.Fatalf("append %s: %v", id, err)
		}
	}
	got, err := RecentSessions(path, 2)
	if err != nil {
		t.Fatalf("recent: %v", err)
	}
	if len(got) != 2 {
		t.Fatalf("want 2 summaries, got %d", len(got))
	}
	if got[0].SessionID != "session-b" || got[1].SessionID != "session-c" {
		t.Fatalf("want [b c] oldest-first, got [%s %s]", got[0].SessionID, got[1].SessionID)
	}
}

func TestRecentSessionsFewerThanN(t *testing.T) {
	path := auditFixture(t)
	_ = AppendSession(path, sampleSummary("session-a"))
	got, err := RecentSessions(path, 5)
	if err != nil {
		t.Fatalf("recent: %v", err)
	}
	if len(got) != 1 || got[0].SessionID != "session-a" {
		t.Fatalf("want [a], got %+v", got)
	}
}

func TestRecentSessionsMissingOrZero(t *testing.T) {
	if got, err := RecentSessions(auditFixture(t), 5); err != nil || got != nil {
		t.Fatalf("missing chain: want (nil,nil), got (%+v,%v)", got, err)
	}
	path := auditFixture(t)
	_ = AppendSession(path, sampleSummary("session-a"))
	if got, err := RecentSessions(path, 0); err != nil || got != nil {
		t.Fatalf("n=0: want (nil,nil), got (%+v,%v)", got, err)
	}
}