package stdio

import (
	"bufio"
	"encoding/json"
	"io"
	"strings"
	"sync"
	"testing"
	"time"
)

// historying serves a bundle whose one tool, "history", runs run, answering each mesh/state ask with
// answer beside the loop, as the runtime does; it returns what the bundle asked.
func historying(t *testing.T, answer func(message) map[string]any, run func()) []message {
	t.Helper()
	t.Setenv(ServedAs, "issues")
	inR, inW := io.Pipe()
	outR, outW := io.Pipe()
	go func() {
		_ = ServeOn("", []Tool{{Name: "history", Run: func(map[string]any) (any, error) { run(); return "done", nil }}}, inR, outW)
	}()
	var wmu, amu sync.Mutex
	var asked []message
	send := func(m map[string]any) {
		m["jsonrpc"] = "2.0"
		b, _ := json.Marshal(m)
		wmu.Lock()
		defer wmu.Unlock()
		_, _ = inW.Write(append(b, '\n'))
	}
	done := make(chan struct{})
	go func() {
		lines := bufio.NewScanner(outR)
		for lines.Scan() {
			var m message
			if json.Unmarshal(lines.Bytes(), &m) != nil {
				continue
			}
			if strings.HasPrefix(m.Method, "mesh/state.") {
				amu.Lock()
				asked = append(asked, m)
				amu.Unlock()
				a := answer(m)
				a["id"] = m.ID
				send(a)
				continue
			}
			if m.Method == "" {
				close(done)
				return
			}
		}
	}()
	send(map[string]any{"id": 1, "method": "tools/call", "params": map[string]any{"name": "history"}})
	t.Cleanup(func() { _ = inW.Close() })
	select {
	case <-done:
	case <-time.After(10 * time.Second):
		t.Fatal("the bundle did not answer")
	}
	amu.Lock()
	defer amu.Unlock()
	return asked
}

// History asks mesh/state.history with the state and the key alone, and hands back every kept value oldest
// first, a delete with its null value; nothing kept is an empty history; a refusal is the runtime's error
// (novox/hq ADR 0307).
func TestHistoryIsEveryKeptValueOldestFirst(t *testing.T) {
	kept := []map[string]any{
		{"key": "401", "value": map[string]any{"status": "open"}, "revision": 4, "op": "put", "at": "2026-10-10T19:46:00Z"},
		{"key": "401", "value": map[string]any{"status": "fixing"}, "revision": 9, "op": "put", "at": "2026-10-11T08:01:02Z"},
		{"key": "401", "value": nil, "revision": 12, "op": "delete", "at": "2026-10-11T09:30:00+02:00"},
	}
	var got, none, null []StateRevision
	var refused error
	asked := historying(t, func(m message) map[string]any {
		var p map[string]any
		_ = json.Unmarshal(m.Params, &p)
		switch {
		case p["state"] != "issues":
			return map[string]any{"error": map[string]any{"code": -32000, "message": "issues was issued no state " + p["state"].(string)}}
		case p["key"] == "401":
			return map[string]any{"result": kept}
		case p["key"] == "402":
			return map[string]any{"result": nil}
		}
		return map[string]any{"result": []any{}}
	}, func() {
		var err error
		if got, err = State("issues").History("401"); err != nil {
			t.Errorf("history of 401: %v", err)
		}
		if none, err = State("issues").History("999"); err != nil {
			t.Errorf("history of 999: %v", err)
		}
		if null, err = State("issues").History("402"); err != nil {
			t.Errorf("history of 402: %v", err)
		}
		var h []StateRevision
		h, refused = State("elsewhere.issues").History("401")
		if h != nil {
			t.Errorf("a refused history handed back %v", h)
		}
	})

	if len(asked) != 4 {
		t.Fatalf("asked %d times, not 4", len(asked))
	}
	var p map[string]any
	_ = json.Unmarshal(asked[0].Params, &p)
	if asked[0].Method != "mesh/state.history" || p["state"] != "issues" || p["key"] != "401" || len(p) != 2 {
		t.Fatalf("asked %s %v", asked[0].Method, p)
	}

	if len(got) != 3 {
		t.Fatalf("history of 401 is %d values, not 3: %+v", len(got), got)
	}
	want := []struct {
		rev   uint64
		op    string
		value string
		at    time.Time
	}{
		{4, "put", `{"status":"open"}`, time.Date(2026, 10, 10, 19, 46, 0, 0, time.UTC)},
		{9, "put", `{"status":"fixing"}`, time.Date(2026, 10, 11, 8, 1, 2, 0, time.UTC)},
		{12, "delete", `null`, time.Date(2026, 10, 11, 7, 30, 0, 0, time.UTC)},
	}
	for i, w := range want {
		r := got[i]
		if r.Key != "401" || r.Revision != w.rev || r.Op != w.op || string(r.Value) != w.value || !r.At.Equal(w.at) {
			t.Fatalf("value %d is %+v, not %+v", i, r, w)
		}
	}
	if none == nil || len(none) != 0 || null == nil || len(null) != 0 {
		t.Fatalf("nothing kept read as %v and %v, not an empty history", none, null)
	}
	if refused == nil || !strings.Contains(refused.Error(), "issued no state elsewhere.issues") {
		t.Fatalf("a state not issued answered %v", refused)
	}
}