package main

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

	stdio "git.novox.be/novox/mesh-sdk/go"
)

// memory is Store kept in this process with the bus's compare-and-set: a create is refused when the key
// has a value, an update when its revision is not the one given — each refusal stdio.ErrChanged, as the
// runtime answers it.
type memory struct {
	mu   sync.Mutex
	rev  uint64
	data map[string]map[string]Entry
	// fail, when set, is the error the next write of that state answers.
	fail map[string]error
}

func newMemory() *memory {
	return &memory{data: map[string]map[string]Entry{IssuesState: {}, CountersState: {}, GroomingState: {}, ReservationsState: {}}, fail: map[string]error{}}
}

func (m *memory) bucket(state string) (map[string]Entry, error) {
	b, ok := m.data[state]
	if !ok {
		return nil, fmt.Errorf("%s is not declared", state)
	}
	return b, nil
}

func (m *memory) Get(state, key string) (*Entry, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	b, err := m.bucket(state)
	if err != nil {
		return nil, err
	}
	e, ok := b[key]
	if !ok {
		return nil, nil
	}
	return &Entry{Value: append(json.RawMessage(nil), e.Value...), Revision: e.Revision}, nil
}

func (m *memory) write(state, key string, value any, check func(Entry, bool) bool) (uint64, error) {
	raw, err := json.Marshal(value)
	if err != nil {
		return 0, err
	}
	m.mu.Lock()
	defer m.mu.Unlock()
	if err := m.fail[state]; err != nil {
		delete(m.fail, state)
		return 0, err
	}
	b, err := m.bucket(state)
	if err != nil {
		return 0, err
	}
	e, ok := b[key]
	if !check(e, ok) {
		return 0, fmt.Errorf("%s.%s: %w", state, key, stdio.ErrChanged)
	}
	m.rev++
	b[key] = Entry{Value: raw, Revision: m.rev}
	return m.rev, nil
}

func (m *memory) Create(state, key string, value any) (uint64, error) {
	return m.write(state, key, value, func(_ Entry, there bool) bool { return !there })
}

func (m *memory) Update(state, key string, value any, revision uint64) (uint64, error) {
	if revision == 0 {
		return 0, errors.New("an update names the revision it read")
	}
	return m.write(state, key, value, func(e Entry, there bool) bool { return there && e.Revision == revision })
}

func (m *memory) put(state, key string, value any) {
	_, _ = m.write(state, key, value, func(Entry, bool) bool { return true })
}

func (m *memory) Keys(state string) ([]string, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	b, err := m.bucket(state)
	if err != nil {
		return nil, err
	}
	var keys []string
	for k := range b {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	return keys, nil
}

// Increment is the SDK's (mesh-sdk go/state.go), over this store.
func (m *memory) Increment(state, key string, attempts int) (uint64, error) {
	for i := 0; i < attempts; i++ {
		e, err := m.Get(state, key)
		if err != nil {
			return 0, err
		}
		var next uint64 = 1
		if e == nil {
			_, err = m.Create(state, key, next)
		} else {
			var n uint64
			if err := json.Unmarshal(e.Value, &n); err != nil {
				return 0, err
			}
			next = n + 1
			_, err = m.Update(state, key, next, e.Revision)
		}
		if err == nil {
			return next, nil
		}
		if !errors.Is(err, stdio.ErrChanged) {
			return 0, err
		}
	}
	return 0, fmt.Errorf("%s: %w", key, stdio.ErrChanged)
}

func (m *memory) counter(t *testing.T) uint64 {
	t.Helper()
	e, _ := m.Get(CountersState, IssueCounter)
	if e == nil {
		return 0
	}
	n, err := strconv.ParseUint(string(e.Value), 10, 64)
	if err != nil {
		t.Fatalf("the counter holds %s", e.Value)
	}
	return n
}

// said is one event the tracker said.
type said struct {
	Event string
	Body  map[string]any
}

type harness struct {
	*Tracker
	mem      *memory
	mu       sync.Mutex
	events   []said
	settings Settings
	emitErr  error
}

func newHarness(t *testing.T) *harness {
	t.Helper()
	h := &harness{mem: newMemory(), settings: Settings{FirstNumber: 365, Owners: []string{
		"hq", "mesh-catalog", "mesh-controller", "mesh-host", "mesh-sdk", "mesh-tools",
		"mesh-catalog modules/nats", "mesh-catalog modules/records", "mesh-catalog modules/mesh-issues"}}}
	clock := time.Date(2026, 10, 10, 12, 0, 0, 0, time.UTC)
	h.Tracker = &Tracker{
		Store: h.mem,
		Emit: func(event string, body any) error {
			h.mu.Lock()
			defer h.mu.Unlock()
			if h.emitErr != nil {
				return h.emitErr
			}
			raw, _ := json.Marshal(body)
			var m map[string]any
			_ = json.Unmarshal(raw, &m)
			h.events = append(h.events, said{event, m})
			return nil
		},
		Settings: func() (Settings, error) { return h.settings, nil },
		Now:      func() time.Time { return clock },
		Logf:     t.Logf,
		Sleep:    func(time.Duration) {},
	}
	return h
}

func (h *harness) said() []said {
	h.mu.Lock()
	defer h.mu.Unlock()
	return append([]said(nil), h.events...)
}

func (h *harness) open(t *testing.T, title string, located ...string) uint64 {
	t.Helper()
	o, err := h.Open(OpenAsk{Title: title, Report: "seen: " + title, LocatedIn: located})
	if err != nil {
		t.Fatalf("open %q: %v", title, err)
	}
	return o.Number
}

// fixing moves an issue to fixing, as the agent that starts its fix does (ADR 0283).
func (h *harness) fixing(t *testing.T, n uint64) {
	t.Helper()
	if _, err := h.Move(MoveAsk{Number: n, Status: StatusFixing, By: "fix@g14"}); err != nil {
		t.Fatalf("move %d to fixing: %v", n, err)
	}
}

// call runs one verb as the tool runner does: by its tool, with arguments as JSON gives them.
func (h *harness) call(t *testing.T, verb string, args map[string]any) (any, error) {
	t.Helper()
	for _, tool := range Tools(h.Tracker) {
		if tool.Name == Seat+"."+verb {
			raw, _ := json.Marshal(args)
			var m map[string]any
			_ = json.Unmarshal(raw, &m)
			return tool.Run(m)
		}
	}
	t.Fatalf("no verb %s", verb)
	return nil, nil
}

// snapshot is every value of a state, by key, as kept now.
func (m *memory) snapshot(state string) map[string]string {
	m.mu.Lock()
	defer m.mu.Unlock()
	out := map[string]string{}
	for k, e := range m.data[state] {
		out[k] = string(e.Value)
	}
	return out
}