package bus_test

import (
	"encoding/json"
	"errors"
	"fmt"
	"sync"
	"testing"
	"time"

	"github.com/novox/mesh-tools/node-tools/internal/bus"
	mt "github.com/novox/mesh-tools/node-tools/internal/meshtest"
)

// streamMesh is a mesh with the mail module's own stream MAIL, and a connection on anchor following the
// memberships of the modules named.
func streamMesh(t *testing.T, memberships ...bus.Membership) (*mt.Mesh, *bus.Conn) {
	t.Helper()
	mesh := mt.New(t)
	mesh.ModuleStream(t, "mail", "MAIL")
	for _, m := range memberships {
		mesh.Issue(t, m)
	}
	conn, err := bus.Connect(bus.Credential{URL: mt.URL(t), Module: "node-tools", Node: "anchor"})
	if err != nil {
		t.Fatal(err)
	}
	conn.Logf = func(string, ...any) {}
	t.Cleanup(conn.Close)
	for _, m := range memberships {
		conn.Follow(m.Module)
	}
	mt.Until(t, func() error {
		for _, m := range memberships {
			if conn.Membership(m.Module) == nil {
				return errors.New(m.Module + " not issued yet")
			}
		}
		return nil
	})
	return mesh, conn
}

// novox/hq ADR 0363 §2, §8 (issue 725): an event one of the module's streams carries is published on that
// stream's subject and kept by that stream alone; any other event of it goes to EVENTS as before.
func TestAnEventADeclaredStreamCarriesIsPublishedOnItsSubjectAlone(t *testing.T) {
	mail := mt.MembershipOf("mail", "anchor", true, nil)
	mail.Streams = []bus.StreamIssued{{Stream: "MAIL", Events: []string{"mail.*.message.added"},
		Subject: "mesh.stream.mail.event.{event}"}}
	mesh, conn := streamMesh(t, mail)

	landed := mesh.NextEvent(t, "mesh.stream.mail.event.>")
	if err := conn.PublishAs("mail", bus.Envelope{Key: "mail.home.message.added", Body: json.RawMessage(`{"id":1}`)}); err != nil {
		t.Fatal(err)
	}
	select {
	case got := <-landed:
		if got != "mesh.stream.mail.event.mail.home.message.added" {
			t.Errorf("published on %s", got)
		}
	case <-time.After(5 * time.Second):
		t.Fatal("the event did not land on its stream's subject")
	}
	if err := conn.PublishAs("mail", bus.Envelope{Key: "status", Body: json.RawMessage(`{}`)}); err != nil {
		t.Fatal(err)
	}
	if n := mesh.Messages(t, "MAIL"); n != 1 {
		t.Errorf("MAIL holds %d messages, want the one event it carries", n)
	}
	if n := mesh.Messages(t, "EVENTS"); n != 1 {
		t.Errorf("EVENTS holds %d messages, want only the event no stream carries", n)
	}
}

// novox/hq ADR 0363 §8 (issue 725): a module hears, beside EVENTS, every module stream its membership names,
// one event at a time, with the key it reads on EVENTS; a membership naming none hears EVENTS alone.
func TestAModuleHearsEveryStreamItsMembershipNames(t *testing.T) {
	reader := mt.MembershipOf("reader", "anchor", false, nil)
	mesh, conn := streamMesh(t, reader)
	mesh.Consumer(t, "anchor", "reader", []string{"mesh.mod.alpha.event.>"}, 5*time.Second)
	mesh.ConsumerOn(t, "MAIL", "anchor", "reader", []string{"mesh.stream.mail.event.mail.home.>"}, 5*time.Second)

	var mu sync.Mutex
	heard := map[string]int{}
	handling := 0
	stop, err := conn.ConsumeAs("reader", func(env bus.Envelope) error {
		mu.Lock()
		handling++
		if handling > 1 {
			t.Error("two events were handed to the module at once")
		}
		mu.Unlock()
		time.Sleep(50 * time.Millisecond)
		mu.Lock()
		handling--
		heard[env.Key]++
		mu.Unlock()
		return nil
	})
	if err != nil {
		t.Fatal(err)
	}
	t.Cleanup(stop)
	count := func(key string) int {
		mu.Lock()
		defer mu.Unlock()
		return heard[key]
	}

	// Its membership names no stream: EVENTS alone, as before.
	mesh.Emit(t, "mesh.mod.alpha.event.happened", map[string]any{"n": 1})
	mesh.Emit(t, "mesh.stream.mail.event.mail.home.message.added", map[string]any{"n": 1})
	mt.Until(t, func() error {
		if count("alpha.happened") != 1 {
			return errors.New("the event on EVENTS was not heard")
		}
		return nil
	})
	if _, notYet := mesh.PendingOn(t, "MAIL", "anchor", "reader"); notYet != 1 || count("mail.mail.home.message.added") != 0 {
		t.Fatalf("a module whose membership names no stream heard MAIL (%d not yet delivered)", notYet)
	}

	// Its membership now names its consumer on MAIL: bound, and what waited there is heard.
	reader.Hears = []bus.HeardIssued{{Stream: "MAIL", Consumer: "anchor_reader"}}
	mesh.Issue(t, reader)
	mt.Until(t, func() error {
		if count("mail.mail.home.message.added") != 1 {
			return errors.New("the event on MAIL was not heard")
		}
		return nil
	})
	for n := 2; n <= 4; n++ {
		mesh.Emit(t, "mesh.mod.alpha.event.happened", map[string]any{"n": n})
		mesh.Emit(t, "mesh.stream.mail.event.mail.home.message.added", map[string]any{"n": n})
	}
	mt.Until(t, func() error {
		if a, m := count("alpha.happened"), count("mail.mail.home.message.added"); a != 4 || m != 4 {
			return fmt.Errorf("heard %d on EVENTS and %d on MAIL, want 4 and 4", a, m)
		}
		for _, stream := range []string{"EVENTS", "MAIL"} {
			if ack, notYet := mesh.PendingOn(t, stream, "anchor", "reader"); ack != 0 || notYet != 0 {
				return fmt.Errorf("%s still holds %d unacknowledged, %d undelivered", stream, ack, notYet)
			}
		}
		return nil
	})

	// A membership that stops naming it stops what it reads there.
	reader.Hears = nil
	mesh.Issue(t, reader)
	mt.Until(t, func() error {
		if mesh.Consumers(t, "MAIL") != 1 {
			return errors.New("MAIL's consumer is gone")
		}
		mesh.Emit(t, "mesh.stream.mail.event.mail.home.message.added", map[string]any{"n": 0})
		time.Sleep(300 * time.Millisecond)
		if _, notYet := mesh.PendingOn(t, "MAIL", "anchor", "reader"); notYet == 0 {
			return errors.New("MAIL is still read")
		}
		return nil
	})
}

// novox/hq ADR 0363 §6 (issue 725): a consumer the membership names before the controller made it is bound once
// it exists, without the module's events on EVENTS waiting for it.
func TestAConsumerNamedBeforeItExistsIsBoundOnceItDoes(t *testing.T) {
	restore := bus.RebindEvery
	bus.RebindEvery = 200 * time.Millisecond
	t.Cleanup(func() { bus.RebindEvery = restore })
	reader := mt.MembershipOf("reader", "anchor", false, nil)
	reader.Hears = []bus.HeardIssued{{Stream: "MAIL", Consumer: "anchor_reader"}}
	mesh, conn := streamMesh(t, reader)
	mesh.Consumer(t, "anchor", "reader", []string{"mesh.mod.alpha.event.>"}, 5*time.Second)

	var mu sync.Mutex
	heard := map[string]int{}
	stop, err := conn.ConsumeAs("reader", func(env bus.Envelope) error {
		mu.Lock()
		heard[env.Key]++
		mu.Unlock()
		return nil
	})
	if err != nil {
		t.Fatalf("a consumer on a module stream not made yet kept the module from hearing EVENTS: %v", err)
	}
	t.Cleanup(stop)
	mesh.Emit(t, "mesh.mod.alpha.event.happened", map[string]any{})
	mesh.ConsumerOn(t, "MAIL", "anchor", "reader", []string{"mesh.stream.mail.event.>"}, 5*time.Second)
	mesh.Emit(t, "mesh.stream.mail.event.mail.home.message.added", map[string]any{})
	mt.Until(t, func() error {
		mu.Lock()
		defer mu.Unlock()
		if heard["alpha.happened"] != 1 || heard["mail.mail.home.message.added"] != 1 {
			return fmt.Errorf("heard %v", heard)
		}
		return nil
	})
}