package main

import (
	"encoding/json"
	"fmt"
	"strings"
	"testing"
	"time"

	"github.com/nats-io/nats.go"
)

// A module's code asks at runtime (novox/hq ADR 0349 clause 14, ADR 0370, design 57 S1, issue 685), against a real
// bus whose accounts are the client's and its machine's tool runner's as mesh-controller composes them: the tool
// runner asks for a carried module's config value and is answered; a change is said, so a watch asks again; a key
// the module does not declare, a module not placed on the machine, a secret and a malformed ask are refused, each
// with its reason.

// toolRunner is g14's tool runner on the bus, asking as its account may.
type toolRunner struct {
	t  *testing.T
	nc *nats.Conn
}

func aToolRunner(t *testing.T, b *aBus) *toolRunner {
	t.Helper()
	nc, err := nats.Connect(b.url, nats.UserInfo(node+".node-tools", "x"),
		nats.CustomInboxPrefix("_INBOX."+node+".node-tools"),
		nats.ErrorHandler(func(_ *nats.Conn, _ *nats.Subscription, err error) {
			t.Errorf("the bus refused the tool runner: %v", err)
		}))
	if err != nil {
		t.Fatal(err)
	}
	t.Cleanup(nc.Close)
	return &toolRunner{t: t, nc: nc}
}

func (r *toolRunner) ask(body string) Answered {
	r.t.Helper()
	var a Answered
	deadline := time.Now().Add(10 * time.Second)
	for {
		msg, err := r.nc.Request(AskSubject(node), []byte(body), 2*time.Second)
		if err == nil {
			if err := json.Unmarshal(msg.Data, &a); err != nil {
				r.t.Fatalf("the client answered %s", msg.Data)
			}
			return a
		}
		if time.Now().After(deadline) {
			r.t.Fatalf("the client did not answer %s: %v", body, err)
		}
		time.Sleep(50 * time.Millisecond) // not listening yet
	}
}

func (r *toolRunner) askConfig(module, key string) Answered {
	r.t.Helper()
	return r.ask(fmt.Sprintf(`{"module":%q,"kind":"config","key":%q}`, module, key))
}

// hear collects what the client says moved on this machine.
func (r *toolRunner) hear() chan string {
	r.t.Helper()
	heard := make(chan string, 64)
	if _, err := r.nc.Subscribe("prov.changed."+node+".>", func(m *nats.Msg) {
		heard <- strings.TrimPrefix(m.Subject, "prov.changed."+node+".") + " " + string(m.Data)
	}); err != nil {
		r.t.Fatal(err)
	}
	_ = r.nc.Flush()
	return heard
}

// placed writes an assignment of a module the controller has not handed to the provisioner: placed, no plan.
func (b *aBus) placed(t *testing.T, module string) {
	t.Helper()
	b.put(t, AssignmentsBucket, node+"."+module, fmt.Sprintf(`{"node":%q,"module":%q,"assigned":"2026-10-14T20:00:00Z"}`,
		node, module))
}

func until(t *testing.T, heard chan string, want string) {
	t.Helper()
	deadline := time.After(10 * time.Second)
	for {
		select {
		case got := <-heard:
			if got == want {
				return
			}
		case <-deadline:
			t.Fatalf("the client did not say %s", want)
		}
	}
}

func TestNatsAModulesCodeReadsItsConfigAndIsToldOfAChange(t *testing.T) {
	b := startBus(t)
	e := startEngine(t, nil)
	b.placed(t, "claude-code")
	b.config(t, "claude-code", "managed_settings", `{"spinnerTipsEnabled":false}`)
	runner := aToolRunner(t, b)
	heard := runner.hear()
	aClient(t, b, e, t.TempDir())

	// The value as mesh-config resolved it.
	if a := runner.askConfig("claude-code", "managed_settings"); a.Error != "" || string(a.Value) != `{"spinnerTipsEnabled":false}` {
		t.Fatalf("answered %+v", a)
	}
	// Coming up, it says every module's config moved, so a watch held across its absence asks again.
	until(t, heard, `claude-code {"kind":"config"}`)

	// A change is said, which value and never the value; asked again, the new value.
	b.config(t, "claude-code", "managed_settings", `{"spinnerTipsEnabled":true}`)
	until(t, heard, `claude-code {"kind":"config","key":"managed_settings"}`)
	if a := runner.askConfig("claude-code", "managed_settings"); string(a.Value) != `{"spinnerTipsEnabled":true}` {
		t.Fatalf("after the change, answered %+v", a)
	}

	// Taken off the machine: said, and no longer answered.
	b.del(t, AssignmentsBucket, node+".claude-code")
	until(t, heard, `claude-code {"kind":"config"}`)
	if a := runner.askConfig("claude-code", "managed_settings"); !strings.Contains(a.Error, "not placed on g14") {
		t.Fatalf("a module taken off the machine was answered %+v", a)
	}
}

func TestNatsWhatAModulesCodeMayNotReadIsRefusedWithTheReason(t *testing.T) {
	b := startBus(t)
	e := startEngine(t, nil)
	b.placed(t, "claude-code")
	b.config(t, "claude-code", "managed_settings", `{}`)
	// Resolved for a module the composition does not place on this machine.
	b.config(t, "dunst", "font-size", "13")
	runner := aToolRunner(t, b)
	aClient(t, b, e, t.TempDir())

	for _, c := range []struct{ ask, refused string }{
		{`{"module":"claude-code","kind":"config","key":"no_such_key"}`, "declares no config value no_such_key"},
		{`{"module":"dunst","kind":"config","key":"font-size"}`, "dunst is not placed on g14"},
		{`{"module":"claude-code","kind":"secret","key":"gitea-read"}`, "not answered on the tool runner's word"},
		{`{"module":"claude-code","kind":"bound","key":"mcp-endpoint:url"}`, "not answered yet"},
		{`{"module":"claude-code","kind":"setting","key":"role"}`, "not a kind the client answers"},
		{`{"module":"claude-code","kind":"config"}`, "names its module, its kind and its key"},
		{`{"module":"claude-code","kind":"config","key":"managed_settings","as":"dunst"}`, "names its module, its kind and its key"},
		{`not json`, "names its module, its kind and its key"},
	} {
		a := runner.ask(c.ask)
		if len(a.Value) != 0 || !strings.Contains(a.Error, c.refused) {
			t.Errorf("%s: answered %+v, want refused with %q", c.ask, a, c.refused)
		}
	}
}