package cli

import (
	"context"
	"errors"
	"net"
	"os"
	"path/filepath"
	"strings"
	"testing"
	"time"
)

// anEngineThatClosesFirst listens like the node-engine before mesh-host#80: it writes its answer, if any, and
// closes without reading the request (novox/hq issue 434). It answers one connection.
func anEngineThatClosesFirst(t *testing.T, answer *Answer) string {
	t.Helper()
	socket := filepath.Join(t.TempDir(), "cli.sock")
	l, err := net.Listen("unix", socket)
	if err != nil {
		t.Skipf("no unix socket here: %v", err)
	}
	t.Cleanup(func() { l.Close() })
	go func() {
		conn, err := l.Accept()
		if err != nil {
			return
		}
		if answer != nil {
			_ = WriteAnswer(conn, *answer)
		}
		conn.Close()
	}()
	return socket
}

// aLineTheSocketCannotHold is a request larger than a unix socket buffers, so its write cannot finish before
// the engine reads it — and an engine that closes first makes it fail every time, not only when it loses a race.
func aLineTheSocketCannotHold() []string { return []string{"status", strings.Repeat("x", 4<<20)} }

// An engine that refuses and closes before reading the request is heard: its refusal reaches the caller, not
// the broken pipe its close left the client's write (novox/hq issue 444).
func TestARefusalWrittenBeforeTheRequestIsReadReachesTheCaller(t *testing.T) {
	busy := Refusal("the node-engine is busy: too many lines at once")
	socket := anEngineThatClosesFirst(t, &busy)
	a, err := Ask(context.Background(), socket, aLineTheSocketCannotHold())
	if err != nil {
		t.Fatalf("the engine said %q and the caller heard: %v", busy.Refused, err)
	}
	if a.Refused != busy.Refused || a.Exit != 1 {
		t.Fatalf("the engine said %q and the caller heard %+v", busy.Refused, a)
	}
}

// When the write fails and no answer is waiting, the error says both: what failed, and that no answer came.
func TestAFailedWriteWithNoAnswerSaysBoth(t *testing.T) {
	socket := anEngineThatClosesFirst(t, nil)
	start := time.Now()
	_, err := Ask(context.Background(), socket, aLineTheSocketCannotHold())
	if err == nil {
		t.Fatal("a request the engine never read, and never answered, came back without an error")
	}
	if !strings.Contains(err.Error(), "asking the node-engine") || !strings.Contains(err.Error(), "no answer came") {
		t.Fatalf("the error does not say what failed and that no answer came: %v", err)
	}
	if waited := time.Since(start); waited > 30*time.Second {
		t.Fatalf("waited %s on a connection the engine had closed", waited)
	}
}

// After a failed write only a refusal is taken: nothing can have run, so an answer saying it ran and exited 0
// is an error, never a success (novox/hq issue 444).
func TestAnAnswerOtherThanARefusalAfterAFailedWriteIsAnError(t *testing.T) {
	ran := Answer{Exit: 0, Stdout: []byte("ok")}
	socket := anEngineThatClosesFirst(t, &ran)
	a, err := Ask(context.Background(), socket, aLineTheSocketCannotHold())
	if err == nil {
		t.Fatalf("a request never wholly written came back as success: %+v", a)
	}
	if !strings.Contains(err.Error(), "not a refusal") {
		t.Fatalf("the error does not say the answer was not a refusal: %v", err)
	}
}

// Reading after a failed write never waits longer than the ask already allowed: a peer that never reads and
// never answers is given up on at the context's deadline, not later (novox/hq issue 444).
func TestAFailedWriteWaitsNoLongerThanTheDeadline(t *testing.T) {
	socket := filepath.Join(t.TempDir(), "cli.sock")
	l, err := net.Listen("unix", socket)
	if err != nil {
		t.Skipf("no unix socket here: %v", err)
	}
	t.Cleanup(func() { l.Close() })
	held := make(chan net.Conn, 1)
	go func() {
		conn, err := l.Accept()
		if err != nil {
			return
		}
		held <- conn // neither read nor answered, nor closed, until the test ends
	}()
	t.Cleanup(func() {
		select {
		case c := <-held:
			c.Close()
		default:
		}
	})
	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
	defer cancel()
	start := time.Now()
	_, err = Ask(ctx, socket, aLineTheSocketCannotHold())
	waited := time.Since(start)
	if err == nil {
		t.Fatal("a peer that never read nor answered gave no error")
	}
	if !errors.Is(err, os.ErrDeadlineExceeded) {
		t.Fatalf("the error is not the deadline: %v", err)
	}
	if waited > 3*time.Second {
		t.Fatalf("waited %s with a deadline of 1s", waited)
	}
}