package batch

import (
	"context"
	"errors"
	"io"
	"log/slog"
	"sync"
	"testing"
	"time"

	"git.wntrmute.dev/kyle/sift/internal/dcache"
)

func newRunner(t *testing.T, fetch FetchFunc, cfg Config) *Runner {
	t.Helper()
	db, err := dcache.Open("", 1<<20, slog.New(slog.NewTextHandler(io.Discard, nil)))
	if err != nil {
		t.Fatal(err)
	}
	t.Cleanup(func() { _ = db.Close() })
	return New(db, fetch, cfg, slog.New(slog.NewTextHandler(io.Discard, nil)))
}

func waitStatus(t *testing.T, r *Runner, id, want string) {
	t.Helper()
	deadline := time.Now().Add(3 * time.Second)
	for time.Now().Before(deadline) {
		j, _, ok := r.Status(id)
		if ok && j.Status == want {
			return
		}
		time.Sleep(time.Millisecond)
	}
	j, _, _ := r.Status(id)
	t.Fatalf("job %s never reached %q (now %q)", id, want, j.Status)
}

func TestSerialOrder(t *testing.T) {
	var mu sync.Mutex
	var calls []string
	inflight, peak := 0, 0
	fetch := func(_ context.Context, tgt Target) (Result, error) {
		mu.Lock()
		inflight++
		if inflight > peak {
			peak = inflight
		}
		calls = append(calls, tgt.URL)
		mu.Unlock()
		time.Sleep(time.Millisecond)
		mu.Lock()
		inflight--
		mu.Unlock()
		return Result{Content: "ok " + tgt.URL}, nil
	}
	r := newRunner(t, fetch, Config{})
	id, reused, err := r.Submit(context.Background(), "alice", "fleet", []Target{
		{URL: "https://a.example/"}, {URL: "https://b.example/"}, {URL: "https://c.example/"},
	})
	if err != nil || reused {
		t.Fatalf("submit err=%v reused=%v", err, reused)
	}
	waitStatus(t, r, id, "done")
	mu.Lock()
	order := append([]string(nil), calls...)
	p := peak
	mu.Unlock()
	if len(order) != 3 || order[0] != "https://a.example/" || order[1] != "https://b.example/" || order[2] != "https://c.example/" {
		t.Fatalf("order %v", order)
	}
	if p != 1 {
		t.Fatalf("peak inflight %d, want 1 (serial)", p)
	}
}

func TestFailureIsolation(t *testing.T) {
	fetch := func(_ context.Context, tgt Target) (Result, error) {
		if tgt.URL == "https://b.example/" {
			return Result{}, errors.New("upstream 500")
		}
		return Result{Content: "ok " + tgt.URL}, nil
	}
	r := newRunner(t, fetch, Config{})
	id, _, err := r.Submit(context.Background(), "alice", "fleet", []Target{
		{URL: "https://a.example/"}, {URL: "https://b.example/"}, {URL: "https://c.example/"},
	})
	if err != nil {
		t.Fatal(err)
	}
	waitStatus(t, r, id, "partial")
	j, ts, ok := r.Status(id)
	if !ok {
		t.Fatal("no job")
	}
	if j.Status != "partial" || j.TargetsDone != 3 {
		t.Fatalf("job %+v", j)
	}
	if ts[0].Status != "done" || ts[1].Status != "failed" || ts[2].Status != "done" {
		t.Fatalf("statuses %+v", ts)
	}
	if ts[1].Error == "" {
		t.Fatal("failed target missing error")
	}
	if ts[0].Result == nil || ts[0].Result.Content != "ok https://a.example/" {
		t.Fatalf("result %+v", ts[0].Result)
	}
}

func TestIdempotentResubmit(t *testing.T) {
	var mu sync.Mutex
	n := 0
	fetch := func(_ context.Context, tgt Target) (Result, error) {
		mu.Lock()
		n++
		mu.Unlock()
		return Result{Content: "ok"}, nil
	}
	r := newRunner(t, fetch, Config{})
	targets := []Target{{URL: "https://a.example/"}, {URL: "https://b.example/"}}
	id1, reused1, err := r.Submit(context.Background(), "alice", "fleet", targets)
	if err != nil || reused1 {
		t.Fatalf("first submit err=%v reused=%v", err, reused1)
	}
	id2, reused2, err := r.Submit(context.Background(), "alice", "fleet", targets)
	if err != nil || !reused2 || id2 != id1 {
		t.Fatalf("resubmit id=%q reused=%v err=%v", id2, reused2, err)
	}
	waitStatus(t, r, id1, "done")
	mu.Lock()
	calls := n
	mu.Unlock()
	if calls != 2 {
		t.Fatalf("fetched %d times, want 2 (idempotent)", calls)
	}
}

func TestTooManyTargets(t *testing.T) {
	fetch := func(_ context.Context, tgt Target) (Result, error) { return Result{Content: "ok"}, nil }
	r := newRunner(t, fetch, Config{TargetsPerJob: 2})
	three := []Target{{URL: "https://a.example/"}, {URL: "https://b.example/"}, {URL: "https://c.example/"}}
	if _, _, err := r.Submit(context.Background(), "alice", "fleet", three); !errors.Is(err, ErrTooManyTargets) {
		t.Fatalf("want ErrTooManyTargets, got %v", err)
	}
}

func TestCallerBusy(t *testing.T) {
	release := make(chan struct{})
	fetch := func(_ context.Context, tgt Target) (Result, error) {
		<-release // hold the job in the running state
		return Result{Content: "ok"}, nil
	}
	r := newRunner(t, fetch, Config{})
	id, _, err := r.Submit(context.Background(), "alice", "fleet", []Target{{URL: "https://a.example/"}})
	if err != nil {
		t.Fatal(err)
	}
	waitStatus(t, r, id, "running")
	if _, _, err := r.Submit(context.Background(), "alice", "fleet", []Target{{URL: "https://b.example/"}}); !errors.Is(err, ErrCallerBusy) {
		t.Fatalf("want ErrCallerBusy, got %v", err)
	}
	close(release)
}

func TestCancel(t *testing.T) {
	started := make(chan struct{}, 1)
	release := make(chan struct{})
	var mu sync.Mutex
	var calls []string
	fetch := func(_ context.Context, tgt Target) (Result, error) {
		mu.Lock()
		calls = append(calls, tgt.URL)
		mu.Unlock()
		select {
		case started <- struct{}{}:
		default:
		}
		<-release
		return Result{Content: "ok"}, nil
	}
	r := newRunner(t, fetch, Config{})
	id, _, err := r.Submit(context.Background(), "alice", "fleet", []Target{
		{URL: "https://a.example/"}, {URL: "https://b.example/"}, {URL: "https://c.example/"},
	})
	if err != nil {
		t.Fatal(err)
	}
	<-started // first target is in flight
	if !r.Cancel(id) {
		t.Fatal("cancel returned false")
	}
	close(release) // let the in-flight target finish
	waitStatus(t, r, id, "cancelled")
	mu.Lock()
	n := len(calls)
	mu.Unlock()
	if n != 1 {
		t.Fatalf("cancelled after %d fetches, want 1", n)
	}
	_, ts, ok := r.Status(id)
	if !ok {
		t.Fatal("no job")
	}
	if ts[0].Status != "done" {
		t.Fatalf("in-flight target should be stored done: %+v", ts[0])
	}
	if ts[1].Status != "pending" || ts[2].Status != "pending" {
		t.Fatalf("later targets must stay pending: %+v", ts[1:])
	}
}

func TestPanicRecovered(t *testing.T) {
	fetch := func(_ context.Context, tgt Target) (Result, error) {
		if tgt.URL == "https://b.example/" {
			panic("boom")
		}
		return Result{Content: "ok"}, nil
	}
	r := newRunner(t, fetch, Config{})
	id, _, err := r.Submit(context.Background(), "alice", "fleet", []Target{
		{URL: "https://a.example/"}, {URL: "https://b.example/"}, {URL: "https://c.example/"},
	})
	if err != nil {
		t.Fatal(err)
	}
	waitStatus(t, r, id, "partial")
	_, ts, _ := r.Status(id)
	if ts[0].Status != "done" || ts[1].Status != "failed" || ts[2].Status != "done" {
		t.Fatalf("statuses %+v", ts)
	}
	if ts[1].Error == "" {
		t.Fatal("panic target missing error")
	}
}