package main

import (
	"context"
	"errors"
	"fmt"
	"log"
	"strings"
	"time"

	hexisclient "github.com/kami/hexis/pkg/client"
	"github.com/kami/maven/internal/router"
	"github.com/kami/maven/internal/store"
)

// praxisCapability is one arm of the Praxis act dispatch. This is an interface
// rather than a map[string]func because each arm carries its own state: the
// verb aliases it answers to, the trace name it records, and its own reply
// formatting. The dispatch grows an arm per Praxis capability, so a new one is
// added to praxisCapabilities below and nothing else changes.
type praxisCapability interface {
	// aliases are the verbs (router fn slots, EN and RU) this capability answers to.
	aliases() []string
	// handle runs the capability and returns the user-facing reply.
	handle(ctx context.Context, h *reactiveHandler, px *praxisClient, dec router.Decision) string
}

// praxisCapabilities is the registry handlePraxisAct consults, in order.
var praxisCapabilities = []praxisCapability{
	listAttentionCapability{},
	praxisItemAction{
		verbs:   []string{"acknowledge_item", "принято", "понял", "поняла"},
		ask:     "какой пункт отметить принятым?",
		op:      "acknowledge",
		failure: "не получилось отметить принятым.",
		success: "принято.",
		call: func(ctx context.Context, px *praxisClient, id string) error {
			_, err := px.Acknowledge(ctx, id)
			return err
		},
	},
	praxisItemAction{
		verbs:   []string{"resolve_item", "сделано", "готово", "решено"},
		ask:     "какой пункт отметить сделанным?",
		op:      "resolve",
		failure: "не получилось отметить сделанным.",
		success: "отмечено как сделано.",
		call: func(ctx context.Context, px *praxisClient, id string) error {
			_, err := px.Resolve(ctx, id)
			return err
		},
	},
	praxisItemAction{
		verbs:   []string{"ignore_item", "игнорировать", "неважно"},
		ask:     "какой пункт игнорировать?",
		op:      "ignore",
		failure: "не получилось проигнорировать.",
		success: "проигнорировано.",
		call: func(ctx context.Context, px *praxisClient, id string) error {
			_, err := px.Ignore(ctx, id)
			return err
		},
	},
	praxisItemAction{
		verbs:   []string{"pin_item", "закрепить"},
		ask:     "какой пункт закрепить?",
		op:      "pin",
		failure: "не получилось закрепить.",
		success: "закреплено.",
		call: func(ctx context.Context, px *praxisClient, id string) error {
			_, err := px.Pin(ctx, id, true)
			return err
		},
	},
	listChangesCapability{},
	entityAttentionCapability{},
}

// handlePraxisAct — dispatches ecosystem tool acts through the Praxis tools API.
// Returns "" when the act is not a Praxis verb (the caller falls through to the
// system command executor). Returns a reply string otherwise.
func (h *reactiveHandler) handlePraxisAct(ctx context.Context, dec router.Decision) string {
	if h.ecosystem == nil || h.ecosystem.praxis == nil {
		return ""
	}
	// Every hop of this action shares one correlation ID, assigned here, so a
	// digest that calls attention once and surface N times reads as one turn
	// on the Praxis side instead of N+1 unrelated request ids.
	if correlationIDFromCtx(ctx) == "" {
		ctx = withCorrelationID(ctx, newCorrelationID())
	}
	px := h.ecosystem.praxis
	for _, capability := range praxisCapabilities {
		for _, alias := range capability.aliases() {
			if alias == dec.Slots.Fn {
				return capability.handle(ctx, h, px, dec)
			}
		}
	}
	// Not a Praxis verb — let the caller fall through.
	return ""
}

// praxisItemAction is the shared shape of the item-lifecycle capabilities: take
// an item id from the value slot, call one Praxis endpoint, trace the result.
type praxisItemAction struct {
	verbs   []string
	ask     string // reply when no item id was given
	op      string // trace + log name of the operation
	failure string // reply when the Praxis call errors
	success string
	call    func(ctx context.Context, px *praxisClient, id string) error
}

func (a praxisItemAction) aliases() []string { return a.verbs }

func (a praxisItemAction) handle(ctx context.Context, h *reactiveHandler, px *praxisClient, dec router.Decision) string {
	id := dec.Slots.Value
	if id == "" {
		return a.ask
	}
	started := h.now()
	if err := a.call(ctx, px, id); err != nil {
		log.Printf("ecosystem: praxis %s %s: %v", a.op, id, err)
		h.recordEcosystemTrace(ctx, "praxis", a.op, traceStatusForError(err), started,
			mergeFields(traceErrorFields(err), map[string]any{"item_id": id}))
		return a.failure
	}
	h.recordPraxisTrace(ctx, a.op, started, map[string]any{"item_id": id})
	return a.success
}

// listAttentionCapability reads the attention digest and surfaces every item it speaks.
type listAttentionCapability struct{}

func (listAttentionCapability) aliases() []string {
	return []string{"list_attention", "attention", "внимание", "что требует внимания", "что нового"}
}

func (listAttentionCapability) handle(ctx context.Context, h *reactiveHandler, px *praxisClient, _ router.Decision) string {
	started := h.now()
	items, err := px.ListAttention(ctx, 20)
	if err != nil {
		log.Printf("ecosystem: praxis attention: %v", err)
		h.recordEcosystemTrace(ctx, "praxis", "list_attention", traceStatusForError(err),
			started, traceErrorFields(err))
		return "не могу сейчас узнать, что требует внимания."
	}
	if len(items) == 0 {
		return "ничего не требует внимания."
	}
	h.recordPraxisTrace(ctx, "list_attention", started, map[string]any{"count": len(items)})
	var parts []string
	for _, item := range items {
		title, _ := item["title"].(string)
		// importance arrives as JSON number ⇒ float64 over the HTTP contract.
		importance, _ := item["importance"].(float64)
		rule, _ := item["rule"].(string)
		s := title
		if importance > 0 {
			s += fmt.Sprintf(" (важность %d", int(importance))
			if rule != "" {
				s += ": " + rule
			}
			s += ")"
		}
		parts = append(parts, s)

		// Speaking an item surfaces it, it does not acknowledge it
		// (ECOSYSTEM-SPEC.md §2.3: surfaced != acknowledged). Best-effort:
		// a failed surface call must not block delivering the digest.
		if id, ok := item["id"].(string); ok && id != "" {
			if _, err := px.Surface(ctx, id); err != nil {
				log.Printf("ecosystem: praxis surface %s: %v", id, err)
			}
		}
	}
	return "требует внимания: " + strings.Join(parts, "; ")
}

// listChangesCapability reads the recent-changes feed.
type listChangesCapability struct{}

func (listChangesCapability) aliases() []string {
	return []string{"list_changes", "changes", "изменения", "что изменилось"}
}

func (listChangesCapability) handle(ctx context.Context, h *reactiveHandler, px *praxisClient, _ router.Decision) string {
	started := h.now()
	changes, err := px.ListChanges(ctx, 20)
	if err != nil {
		log.Printf("ecosystem: praxis changes: %v", err)
		h.recordEcosystemTrace(ctx, "praxis", "list_changes", traceStatusForError(err),
			started, traceErrorFields(err))
		return "не могу сейчас узнать об изменениях."
	}
	if len(changes) == 0 {
		return "нет изменений."
	}
	h.recordPraxisTrace(ctx, "list_changes", started, map[string]any{"count": len(changes)})
	var parts []string
	for _, c := range changes {
		title, _ := c["title"].(string)
		typ, _ := c["change_type"].(string)
		parts = append(parts, fmt.Sprintf("%s (%s)", title, typ))
	}
	return "изменения: " + strings.Join(parts, "; ")
}

// entityAttentionCapability answers "what's going on with X" by resolving X to
// a canonical Nexus entity and asking Praxis for that entity's attention items
// (Vikunja #272). Unlike listAttentionCapability it is scoped: the entity_id
// travels to Praxis as a query parameter instead of Maven filtering an unscoped
// list client-side, which is what makes the ref canonical end to end.
//
// It also folds in what Maven herself knows about the same entity — facts the
// enrichment worker has already resolved to that entity_id — so one question
// gets one answer across both stores.
type entityAttentionCapability struct{}

// aliases are matched against Slots.Fn, which carries a function slot from the
// act grammar and never free Russian, so only grammar names belong here.
func (entityAttentionCapability) aliases() []string {
	return []string{"entity_attention", "entity_status"}
}

func (entityAttentionCapability) handle(ctx context.Context, h *reactiveHandler, px *praxisClient, dec router.Decision) string {
	subject := dec.Slots.Value
	if subject == "" {
		subject = dec.Slots.Text
	}
	if subject == "" {
		return "про что именно спросить?"
	}
	if h.ecosystem == nil || h.ecosystem.nexus == nil {
		// Without Nexus there is no canonical ref to scope by. Say so rather
		// than quietly answering about something else.
		return "не могу связать это с сущностью — Nexus не настроен."
	}

	started := h.now()
	entityID, displayName, ambiguous, err := h.ecosystem.resolveEntityReference(ctx, subject, nil)
	if err != nil {
		// The subject is his words, so the log gets the same redaction the
		// trace gets. A trace that stores a rune count next to a log line
		// storing the runes is not redacted at all.
		log.Printf("ecosystem: entity attention resolve %s: %v", redactSubject(subject), err)
		h.recordEcosystemTrace(ctx, "nexus", "resolve", traceStatusForError(err), started,
			mergeFields(traceErrorFields(err), map[string]any{"subject": redactSubject(subject)}))
		if unauthorizedEcosystemError(err) {
			return "экосистема отклоняет доступ, проверь токен."
		}
		return "экосистема недоступна, попробуй ещё раз."
	}
	if len(ambiguous) > 0 {
		return "уточни, что именно: " + strings.Join(ambiguous, ", ") + "?"
	}
	if entityID == "" {
		return "не знаю такой сущности."
	}
	if displayName == "" {
		displayName = subject
	}

	queried := h.now()
	items, err := px.ListAttentionForEntity(ctx, entityID, 20)
	if err != nil {
		log.Printf("ecosystem: praxis attention for %s: %v", entityID, err)
		h.recordEcosystemTrace(ctx, "praxis", "entity_attention", traceStatusForError(err),
			queried, mergeFields(traceErrorFields(err), map[string]any{"entity_id": entityID}))
		return "не могу сейчас узнать, что требует внимания по «" + displayName + "»."
	}
	items, scoped := scopedToEntity(items, entityID)
	if !scoped {
		// A Praxis old enough to ignore an unknown query parameter answers the
		// scoped question with the unscoped list. Reading that back as "по
		// «X»: ..." is the exact fabrication the entity ref exists to prevent,
		// so refuse the answer instead of relabelling someone else's items.
		log.Printf("ecosystem: praxis returned unscoped items for %s, refusing to answer", entityID)
		h.recordEcosystemTrace(ctx, "praxis", "entity_attention", traceFailed, queried,
			map[string]any{"entity_id": entityID, "class": "unscoped_response"})
		return "не могу сейчас узнать, что требует внимания по «" + displayName + "»."
	}
	h.recordPraxisTrace(ctx, "entity_attention", queried, map[string]any{
		"entity_id": entityID, "count": len(items),
	})

	var parts []string
	for _, item := range items {
		title, _ := item["title"].(string)
		if title == "" {
			continue
		}
		parts = append(parts, title)
		// Same surfaced != acknowledged rule as the unscoped digest.
		if id, ok := item["id"].(string); ok && id != "" {
			if _, err := px.Surface(ctx, id); err != nil {
				log.Printf("ecosystem: praxis surface %s: %v", id, err)
			}
		}
	}
	if known := h.localFactsForEntity(ctx, entityID); known != "" {
		parts = append(parts, known)
	}
	if len(parts) == 0 {
		return "по «" + displayName + "» ничего нет."
	}
	return "по «" + displayName + "»: " + strings.Join(parts, "; ")
}

// scopedToEntity drops items that carry an entity_id other than the one asked
// about, and reports whether the response can be trusted as scoped at all. An
// item without an entity_id is kept only when at least one sibling carries the
// matching id: a whole page with no entity_id is a Praxis that ignored the
// scope, not a page of untagged items.
func scopedToEntity(items []map[string]any, entityID string) ([]map[string]any, bool) {
	if len(items) == 0 {
		return items, true
	}
	var kept []map[string]any
	var sawMatch, sawMismatch bool
	for _, item := range items {
		id, _ := item["entity_id"].(string)
		switch {
		case id == entityID:
			sawMatch = true
			kept = append(kept, item)
		case id != "":
			sawMismatch = true
		default:
			kept = append(kept, item)
		}
	}
	if sawMatch {
		return kept, true
	}
	if sawMismatch {
		// Some items were tagged and none matched: the far side answered about
		// other entities, so nothing here belongs to this one.
		return nil, true
	}
	return nil, false
}

// localFactsForEntity summarises Maven's own facts already resolved to this
// canonical entity. Empty when the store is unavailable or nothing matched —
// entity-scoped memory is an enrichment of the answer, never a precondition.
func (h *reactiveHandler) localFactsForEntity(ctx context.Context, entityID string) string {
	if h.dataStore == nil || entityID == "" {
		return ""
	}
	const spoken = 3
	// One over the spoken limit, so a truncation can be named rather than
	// passed off as everything she knows.
	facts, err := h.dataStore.FactsByEntity(ctx, entityID, spoken+1)
	if err != nil {
		log.Printf("ecosystem: facts by entity %s: %v", entityID, err)
		return ""
	}
	more := false
	if len(facts) > spoken {
		facts, more = facts[:spoken], true
	}
	var parts []string
	for _, f := range facts {
		if f.Value != "" {
			parts = append(parts, f.Value)
		}
	}
	if len(parts) == 0 {
		return ""
	}
	out := "я помню: " + strings.Join(parts, ", ")
	if more {
		out += ", и это не всё"
	}
	return out
}

// mergeFields overlays b onto a and returns a.
func mergeFields(a, b map[string]any) map[string]any {
	for k, v := range b {
		a[k] = v
	}
	return a
}

// recordPraxisTrace — records a completed Praxis call. Thin wrapper over
// recordEcosystemTrace so every ecosystem hop lands in one table with one
// shape.
func (h *reactiveHandler) recordPraxisTrace(ctx context.Context, operation string, started time.Time, details map[string]any) {
	h.recordEcosystemTrace(ctx, "praxis", operation, traceOK, started, details)
}

// traceStatus classifies an ecosystem call for the trace record. Kept coarse
// on purpose: a trace is read to answer "did this hop work, and how long did
// it take", not to re-derive the error.
const (
	traceOK       = "ok"
	traceFailed   = "failed"  // the call never got an answer
	traceRefused  = "refused" // the far side answered, and said no
	traceAmbig    = "ambiguous"
	traceNotFound = "not_found"
	tracePending  = "pending" // deliberately not done yet, awaiting a confirm
)

// traceStatusForError distinguishes "I could not reach it" from "it answered
// and refused". Both degrade the same way for him and not at all the same way
// for whoever reads the trace: one is a network or a dead service, the other
// is a token, a version or a rejected argument.
func traceStatusForError(err error) string {
	var ee *ecosystemError
	if errors.As(err, &ee) && !ee.Unreachable() {
		return traceRefused
	}
	return traceFailed
}

// redactSubject reduces a user utterance to something safe to persist in a
// trace: its length only. Traces are diagnostics, and his words are not
// diagnostics — the correlation ID is what ties a trace to the turn.
func redactSubject(s string) string {
	return fmt.Sprintf("<%d chars>", len([]rune(s)))
}

// recordEcosystemTrace writes one hop of a cross-service call: which service,
// which operation, the outcome, how long it took, and the correlation ID that
// stitches the hops together. It is written for every outcome, not only
// success — an unrecorded failure is exactly the hop you need when something
// went wrong at 3am.
//
// Traces go to their own store table, never to facts. One act turn produces
// three or four of them, at machine rate, while facts arrive at human rate:
// sharing the table meant the habit profile's 2000-row window, memeval's
// prompt snapshot and the /dash and /history pages all filled with traces and
// stopped seeing his actual facts.
func (h *reactiveHandler) recordEcosystemTrace(ctx context.Context, service, op, status string, started time.Time, fields map[string]any) {
	if h.dataStore == nil {
		return
	}
	tr := store.EcosystemTrace{
		Ts:            h.now(),
		Service:       service,
		Operation:     op,
		Status:        status,
		DurationMs:    h.now().Sub(started).Milliseconds(),
		CorrelationID: correlationIDFromCtx(ctx),
		Fields:        map[string]any{},
	}
	for k, v := range fields {
		switch k {
		case "causation_id":
			tr.CausationID, _ = v.(string)
		case "http_status":
			if n, ok := v.(int); ok {
				tr.HTTPStatus = n
				continue
			}
			tr.Fields[k] = v
		default:
			tr.Fields[k] = v
		}
	}
	if _, err := h.dataStore.WriteEcosystemTrace(ctx, tr); err != nil {
		log.Printf("ecosystem: record trace %s:%s: %v", service, op, err)
	}
}

// unauthorizedEcosystemError reports a credential the far side rejected. It
// gets its own reply: a missing or wrong token looks exactly like an outage to
// him, and "try again" is advice that will never work.
func unauthorizedEcosystemError(err error) bool {
	var ee *ecosystemError
	return errors.As(err, &ee) && ee.Unauthorized()
}

// traceErrorFields describes an ecosystemError for a trace without leaking the
// payload: the HTTP status and the failure class, nothing else.
func traceErrorFields(err error) map[string]any {
	fields := map[string]any{}
	var ee *ecosystemError
	if errors.As(err, &ee) {
		fields["http_status"] = ee.Status
		switch {
		case ee.Unauthorized():
			fields["class"] = "unauthorized"
		case ee.ContractMismatch():
			fields["class"] = "contract_mismatch"
		case ee.Unreachable():
			fields["class"] = "unreachable"
		default:
			fields["class"] = "error"
		}
		return fields
	}
	fields["class"] = "error"
	return fields
}

// handleHexisAct — resolves entity references through Nexus and executes
// matching capabilities through Hexis. Returns a reply string when handled,
// or "" to fall through to the system command executor.
func (h *reactiveHandler) handleHexisAct(ctx context.Context, dec router.Decision) string {
	if h.ecosystem == nil {
		return ""
	}

	// Every hop of this action shares one correlation ID, assigned here so
	// resolution and discovery are traceable even when execution never
	// happens.
	if correlationIDFromCtx(ctx) == "" {
		ctx = withCorrelationID(ctx, newCorrelationID())
	}

	// Resolve the utterance text as an entity reference through Nexus. An
	// ambiguous match must stop and clarify — never guess a mutation target.
	started := h.now()
	entityID, displayName, ambiguous, err := h.ecosystem.resolveEntityReference(ctx, dec.Slots.Text, nil)
	if err != nil {
		h.recordEcosystemTrace(ctx, "nexus", "resolve", traceStatusForError(err), started,
			mergeFields(traceErrorFields(err), map[string]any{"subject": redactSubject(dec.Slots.Text)}))
		if unauthorizedEcosystemError(err) {
			return "экосистема отклоняет доступ, проверь токен."
		}
		// A genuine Nexus dependency failure, not "no such entity" — stop here
		// and report degradation rather than silently falling through to the
		// local command executor (ECOSYSTEM-SPEC.md: services degrade
		// independently, never a silent all-clear).
		return "экосистема недоступна, попробуй ещё раз."
	}
	if len(ambiguous) > 0 {
		h.recordEcosystemTrace(ctx, "nexus", "resolve", traceAmbig, started,
			map[string]any{"candidates": len(ambiguous)})
		return "уточни, что именно: " + strings.Join(ambiguous, ", ") + "?"
	}
	if entityID == "" {
		h.recordEcosystemTrace(ctx, "nexus", "resolve", traceNotFound, started,
			map[string]any{"subject": redactSubject(dec.Slots.Text)})
		return ""
	}
	h.recordEcosystemTrace(ctx, "nexus", "resolve", traceOK, started,
		map[string]any{"entity_id": entityID})

	// Discover Hexis capabilities for this entity. A resolved entity with a
	// genuine Hexis failure must not be treated as "no capabilities" and
	// fall through to unrelated local execution.
	discovered := h.now()
	caps, err := h.ecosystem.discoverCapabilities(ctx, entityID)
	if err != nil {
		h.recordEcosystemTrace(ctx, "hexis", "capabilities", traceStatusForError(err), discovered,
			mergeFields(traceErrorFields(err), map[string]any{"entity_id": entityID}))
		if unauthorizedEcosystemError(err) {
			return "экосистема отклоняет доступ, проверь токен."
		}
		return "экосистема недоступна, попробуй ещё раз."
	}
	h.recordEcosystemTrace(ctx, "hexis", "capabilities", traceOK, discovered,
		map[string]any{"entity_id": entityID, "count": len(caps)})
	if len(caps) == 0 {
		return ""
	}

	// Match the user's verb to a capability by name/description. Collect all
	// matches: more than one is itself ambiguous, so we ask rather than pick
	// the first (ecosystem invariant: no arbitrary target for mutation).
	verb := dec.Slots.Fn
	if verb == "" {
		verb = dec.Slots.Text
	}
	verbLower := strings.ToLower(verb)

	var matches []*hexisclient.Capability
	for i, c := range caps {
		if strings.Contains(strings.ToLower(c.Name), verbLower) ||
			(c.Description != "" && strings.Contains(strings.ToLower(c.Description), verbLower)) {
			matches = append(matches, &caps[i])
		}
	}
	if len(matches) == 0 {
		return ""
	}
	if len(matches) > 1 {
		var names []string
		for _, m := range matches {
			names = append(names, m.Name)
		}
		return "какую команду для " + displayName + ": " + strings.Join(names, ", ") + "?"
	}
	matched := matches[0]

	// Read-only capabilities run immediately; mutating ones are parked for an
	// explicit spoken confirm bound to this capability + target.
	if !matched.ReadOnly {
		h.mu.Lock()
		h.pendingHexis = &pendingHexisExec{
			capabilityID: matched.ID,
			capName:      matched.Name,
			entityID:     entityID,
			displayName:  displayName,
			expiry:       h.now().Add(confirmTTL),
		}
		h.mu.Unlock()
		h.recordEcosystemTrace(ctx, "hexis", "confirmation", tracePending, started,
			map[string]any{"entity_id": entityID, "capability": matched.Name})
		return "выполнить «" + matched.Name + "» для " + displayName + "? скажи «да» или «нет»."
	}

	return h.execHexis(ctx, matched.ID, matched.Name, entityID, displayName)
}

// execHexis runs a resolved capability and records a cross-service trace with
// the correlation ID. It reports command success, never operational recovery
// (Praxis observes recovery independently).
func (h *reactiveHandler) execHexis(ctx context.Context, capID, capName, entityID, displayName string) string {
	started := h.now()
	causationID := correlationIDFromCtx(ctx)
	correlationID, err := h.ecosystem.executeCapability(ctx, capID, entityID, nil)
	traced := withCorrelationID(ctx, correlationID)
	if err != nil {
		log.Printf("ecosystem: hexis execute error (cor=%s): %v", correlationID, err)
		h.recordEcosystemTrace(traced, "hexis", "execute", traceStatusForError(err), started,
			mergeFields(traceErrorFields(err), map[string]any{
				"entity_id": entityID, "capability": capName, "causation_id": causationID,
			}))
		return "не получилось выполнить команду для " + displayName + "."
	}
	// One record per hop: the second write this used to make said the same
	// thing under a different key, in a different shape.
	h.recordEcosystemTrace(traced, "hexis", "execute", traceOK, started, map[string]any{
		"entity_id": entityID, "entity_name": displayName,
		"capability": capName, "causation_id": causationID,
	})
	return "команда выполнена для " + displayName + "."
}