package enginereads

import (
	"context"
	"encoding/json"
	"errors"
	"strings"
	"testing"
	"time"
)

// The answer and the event are judged as the contract lays them out and its reader checks: the layout's version, a node
// that is a name, no empty capability, a time, and an event's why one of the two.
func TestTheAnswerAndTheEventAreJudged(t *testing.T) {
	const at = "2026-11-05T12:00:00Z"
	for name, c := range map[string]struct{ body, bad string }{
		"whole":      {`{"v":1,"node":"ace","manifest-reads":["mesh-config.resolved"],"stated-at":"` + at + `"}`, ""},
		"old layout": {`{"v":2,"node":"ace","stated-at":"` + at + `"}`, "version"},
		"bad node":   {`{"v":1,"node":"a.b","stated-at":"` + at + `"}`, "no node"},
		"empty read": {`{"v":1,"node":"ace","manifest-reads":[" "],"stated-at":"` + at + `"}`, "empty reader"},
		"no time":    {`{"v":1,"node":"ace","stated-at":"yesterday"}`, "RFC 3339"},
	} {
		_, _, err := DecodeAnswer([]byte(c.body))
		if (c.bad == "") != (err == nil) || (err != nil && !strings.Contains(err.Error(), c.bad)) {
			t.Errorf("answer %s: %v, want %q", name, err, c.bad)
		}
	}
	for name, c := range map[string]struct{ body, bad string }{
		"whole":       {`{"v":1,"node":"ace","why":"started","manifest-reads":["a.b"],"at":"` + at + `"}`, ""},
		"returned":    {`{"v":1,"node":"ace","why":"returned","at":"` + at + `"}`, ""},
		"old layout":  {`{"v":2,"node":"ace","why":"started","at":"` + at + `"}`, "version"},
		"no node":     {`{"v":1,"node":"","why":"started","at":"` + at + `"}`, "no node"},
		"another why": {`{"v":1,"node":"ace","why":"bored","at":"` + at + `"}`, "bored"},
		"no time":     {`{"v":1,"node":"ace","why":"started","at":"yesterday"}`, "RFC 3339"},
	} {
		_, err := DecodeChanged([]byte(c.body))
		if (c.bad == "") != (err == nil) || (err != nil && !strings.Contains(err.Error(), c.bad)) {
			t.Errorf("event %s: %v, want %q", name, err, c.bad)
		}
	}
	// Issue 1966 note 155, ADR 0668 §4: a part whose first call of a node timed out, and whose consumer was bound after
	// the node's event was said, calls every node once at the bind, and the node is then held as it answered.
	calls := map[string]int{}
	k := &Keeper{Sync: true, Call: func(node, _ string, _ any) (json.RawMessage, error) {
		calls[node]++
		if node == "ace" && calls[node] == 1 {
			return nil, context.DeadlineExceeded
		}
		return json.RawMessage(`{"v":1,"node":"` + node + `","manifest-reads":["a.b"],"stated-at":"` + at + `"}`), nil
	}}
	k.AskNode("ace", "the first view")
	if k.Statements()["ace"].Answered {
		t.Errorf("a call that timed out reads as answered")
	}
	k.AtBind(func() []string { return []string{"ace", "g14"} })(time.Unix(0, 0))
	if p := k.Present([]string{"ace", "g14"}); len(p["ace"]) != 1 || len(p["g14"]) != 1 || calls["ace"] != 2 || calls["g14"] != 1 {
		t.Errorf("after the bind: present %v, calls %v", p, calls)
	}
	// Review round 1 (ADR 0668 §3): a node whose engine answers nothing reads as its record at the first fault of the call
	// made once, while the kept call asks on; what the kept call answers then stands.
	var during Statement
	f := &Keeper{Sync: true, Fallback: func(string) ([]string, bool) { return []string{"r.s"}, true },
		Once: func(string, string, any) (json.RawMessage, error) {
			return nil, errors.New("nats: no responders available for request")
		}}
	f.Call = func(node, _ string, _ any) (json.RawMessage, error) {
		during = f.Statements()[node]
		return json.RawMessage(`{"v":1,"node":"` + node + `","manifest-reads":["a.b"],"stated-at":"` + at + `"}`), nil
	}
	f.AskNode("g14", "the first view")
	if during.From != FromRecord || during.Answered || f.Statements()["g14"].From != FromVerb {
		t.Errorf("while the kept call asked g14 read %+v; after it %+v", during, f.Statements()["g14"])
	}
	// ADR 0668 §3: a node unanswered keeps when it first was not, across asks; past the bound it is unanswered while its
	// machine is heard, none while away, and none once it answers.
	clock := time.Date(2026, 11, 10, 3, 0, 0, 0, time.UTC)
	answers := false
	u := &Keeper{Sync: true, Now: func() time.Time { return clock }, Call: func(node, _ string, _ any) (json.RawMessage, error) {
		if answers {
			return json.RawMessage(`{"v":1,"node":"` + node + `","manifest-reads":["a.b"],"stated-at":"` + at + `"}`), nil
		}
		return nil, context.DeadlineExceeded
	}}
	first := clock
	u.AskNode("ace", "the first view")
	clock = clock.Add(6 * time.Minute)
	u.AskNode("ace", "asked on")
	heard := func(string) bool { return true }
	if got := u.Unanswered([]string{"ace"}, heard, 5*time.Minute, clock); !got["ace"].Equal(first) ||
		len(u.Unanswered([]string{"ace"}, func(string) bool { return false }, 5*time.Minute, clock)) != 0 {
		t.Errorf("unanswered past the bound: %v", got)
	}
	answers = true
	u.AskNode("ace", "answered")
	if got := u.Unanswered([]string{"ace"}, heard, 5*time.Minute, clock); len(got) != 0 || !u.Statements()["ace"].UnansweredSince.IsZero() {
		t.Errorf("an answered node is unanswered: %v", got)
	}
	if Verb != "manifest-reads" || Event != "manifest-reads-changed" || Consumes != "node-engine.manifest-reads-changed" || Invoke != "seat:node-engine.manifest-reads" {
		t.Errorf("the names are %s %s %s %s", Verb, Event, Consumes, Invoke)
	}
}

// ADR 0668 §3, ADR 0596 §2 (review round 3): the wait of a part's kept manifest-reads calls. With Arm, a node unanswered
// has its bound kept, and only its expiry asks whether its machine is heard, once: heard, the finding is written at the
// part's clock and the node asked again; away, none; answered, it is cleared. With no Arm, heard is weighed at each step.
func TestReadsCallsSayAnUnansweredNodeHeard(t *testing.T) {
	clock := time.Date(2026, 11, 10, 3, 0, 0, 0, time.UTC)
	answers, calls := false, 0
	k := &Keeper{Sync: true, Now: func() time.Time { return clock }, Call: func(node, _ string, _ any) (json.RawMessage, error) {
		calls++
		if answers {
			return json.RawMessage(`{"v":1,"node":"` + node + `","manifest-reads":["a.b"],"stated-at":"2026-11-10T03:00:00Z"}`), nil
		}
		return nil, context.DeadlineExceeded
	}}
	for name, armed := range map[string]bool{"armed": true, "by its own knowledge": false} {
		answers, calls = false, 0
		k.Forget("ace")
		first := clock
		k.AskNode("ace", "the first view")
		heard, asked := true, 0
		raised, cleared := map[string]UnansweredCall{}, map[string]int{}
		bounds := map[string]time.Time{}
		c := &ReadsCalls{Keeper: k, Nodes: func() []string { return []string{"ace", "g14"} }, Bound: 5 * time.Minute,
			Now:   func() time.Time { return clock.Add(time.Second) },
			Heard: func(context.Context, string) (bool, error) { asked++; return heard, nil },
			Raise: func(_ context.Context, u UnansweredCall) error { raised[u.Node] = u; return nil },
			Clear: func(_ context.Context, node string) error { cleared[node]++; delete(raised, node); return nil }}
		if armed {
			c.Arm = func(_ context.Context, node string, ends time.Time) error { bounds[node] = ends; return nil }
		}
		c.Step(context.Background())
		if armed && (asked != 0 || !bounds["ace"].Equal(first.Add(5*time.Minute)) || len(raised) != 0) {
			t.Errorf("%s: a step before the bound asked heard %d times, bounds %v, raised %v", name, asked, bounds, raised)
		}
		clock = clock.Add(6 * time.Minute)
		heard, asked = false, 0
		if armed {
			c.Expired(context.Background(), "ace")
		} else {
			c.Step(context.Background())
		}
		if len(raised) != 0 || asked != 1 {
			t.Errorf("%s: away, raised %v, heard asked %d times", name, raised, asked)
		}
		heard, asked, calls = true, 0, 0
		if armed {
			c.Expired(context.Background(), "ace")
		} else {
			c.Step(context.Background())
		}
		if u, ok := raised["ace"]; !ok || !u.Since.Equal(first) || !u.At.Equal(clock.Add(time.Second)) || asked != 1 || calls != 1 {
			t.Errorf("%s: heard past the bound, raised %+v, heard asked %d, called %d", name, raised, asked, calls)
		}
		answers = true
		k.AskNode("ace", "answered")
		c.Step(context.Background())
		if _, ok := raised["ace"]; ok || cleared["ace"] == 0 {
			t.Errorf("%s: answered, raised %v, cleared %v", name, raised, cleared)
		}
		clock = clock.Add(time.Hour)
	}
	if CallID("ace") != "manifest-reads.ace" {
		t.Errorf("the call's id is %s", CallID("ace"))
	}
	if n, ok := BoundOf(BoundPrefix + "ace"); !ok || n != "ace" {
		t.Errorf("the bound's node is %q %v", n, ok)
	}
}