package main

import (
	"bytes"
	"context"
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"log"
	"net/http"
	"net/url"
	"strings"
	"time"

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

// ecosystemCorrelationKey carries a per-call correlation ID through context
// so every ecosystem client (Nexus, Praxis, Hexis) tags its request with the
// same ID, letting a single Maven-initiated action be traced end to end.
type ecosystemCorrelationKey struct{}

func withCorrelationID(ctx context.Context, id string) context.Context {
	return context.WithValue(ctx, ecosystemCorrelationKey{}, id)
}

func correlationIDFromCtx(ctx context.Context) string {
	id, _ := ctx.Value(ecosystemCorrelationKey{}).(string)
	return id
}

// ecosystemAPIVersion is the contract version Maven speaks to Nexus and
// Praxis. It is sent on every request so a service that has moved on can
// refuse or adapt explicitly instead of misreading an older payload.
const ecosystemAPIVersion = "v1"

// mavenRequester identifies the calling system on every ecosystem request, so
// a trace on the far side can attribute a call to Maven rather than to an
// anonymous HTTP client.
const mavenRequester = "maven"

// ecosystemHTTP is the JSON transport every ecosystem client shares: one base
// URL, one bearer token, and the header set the contract requires on each
// request. Nexus and Praxis differ only in the service name and the version
// header, so both embed this rather than repeating build, send and classify.
type ecosystemHTTP struct {
	service       string // "nexus", "praxis" — the name errors and traces carry
	versionHeader string
	baseURL       string
	token         string
	httpClient    *http.Client
}

func newEcosystemHTTP(service, versionHeader, baseURL string) ecosystemHTTP {
	return ecosystemHTTP{
		service:       service,
		versionHeader: versionHeader,
		baseURL:       baseURL,
		httpClient:    &http.Client{Timeout: 10 * time.Second},
	}
}

// setHeaders stamps the version, requester, auth and correlation headers common
// to every outgoing ecosystem request. The token may be empty, which means the
// transport itself is trusted (loopback or unix socket).
//
// The correlation ID is read from the request's own context and never minted
// here. Minting one per request sent the far side an ID that existed nowhere on
// this side, and gave a single multi-hop action as many unrelated IDs as it
// made calls. Callers that start an action assign the ID once (handleHexisAct,
// handlePraxisAct, resolveEntityReference) and every hop inherits it.
func (t *ecosystemHTTP) setHeaders(req *http.Request) {
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set(t.versionHeader, ecosystemAPIVersion)
	req.Header.Set("Accept", "application/json")
	req.Header.Set("X-Requested-By", mavenRequester)
	if t.token != "" {
		req.Header.Set("Authorization", "Bearer "+t.token)
	}
	if id := correlationIDFromCtx(req.Context()); id != "" {
		req.Header.Set("X-Correlation-ID", id)
	}
}

// call sends one request and decodes the JSON answer into out, which may be nil
// when the body carries nothing worth reading. op is the logical operation name
// for errors and traces: the path carries the query string, and after entity
// scoping that means an entity id in every log line built from the error, next
// to a trace that redacts far less than that.
//
// Every failure is an *ecosystemError, including the transport and decode ones.
// Some of these paths mutate remote state, and the question worth answering
// afterwards is whether the call never left or was refused.
func (t *ecosystemHTTP) call(ctx context.Context, method, op, path string, payload, out any) error {
	var body io.Reader
	if payload != nil {
		data, err := json.Marshal(payload)
		if err != nil {
			return &ecosystemError{Service: t.service, Op: op, Err: err}
		}
		body = bytes.NewReader(data)
	}
	req, err := http.NewRequestWithContext(ctx, method, t.baseURL+path, body)
	if err != nil {
		return &ecosystemError{Service: t.service, Op: op, Err: err}
	}
	t.setHeaders(req)

	resp, err := t.httpClient.Do(req)
	if err != nil {
		return &ecosystemError{Service: t.service, Op: op, Err: err}
	}
	defer resp.Body.Close()
	if resp.StatusCode != 200 {
		return httpError(t.service, op, resp.StatusCode)
	}
	if out == nil {
		return nil
	}
	if err := json.NewDecoder(resp.Body).Decode(out); err != nil {
		return &ecosystemError{Service: t.service, Op: op, Status: resp.StatusCode, Err: err}
	}
	return nil
}

// getJSON performs a GET and decodes the JSON body into out.
func (t *ecosystemHTTP) getJSON(ctx context.Context, op, path string, out any) error {
	return t.call(ctx, http.MethodGet, op, path, nil, out)
}

// postJSON posts a JSON payload and decodes the JSON answer into out.
func (t *ecosystemHTTP) postJSON(ctx context.Context, op, path string, payload, out any) error {
	return t.call(ctx, http.MethodPost, op, path, payload, out)
}

// ecosystemError is the typed failure every ecosystem client returns, so
// callers can tell a transport failure from a refusal from a contract
// mismatch without matching on message text. The distinction matters:
// "the service is down" and "the service rejected my version" degrade the
// same way to the user but not to whoever reads the trace.
type ecosystemError struct {
	Service string // "nexus", "praxis", "hexis"
	Op      string // logical operation, e.g. "resolve"
	Status  int    // HTTP status, 0 when the call never got an answer
	Err     error
}

func (e *ecosystemError) Error() string {
	if e.Status != 0 {
		return fmt.Sprintf("%s %s: http %d: %v", e.Service, e.Op, e.Status, e.Err)
	}
	return fmt.Sprintf("%s %s: %v", e.Service, e.Op, e.Err)
}

func (e *ecosystemError) Unwrap() error { return e.Err }

// Unauthorized reports a rejected or missing credential.
func (e *ecosystemError) Unauthorized() bool {
	return e.Status == http.StatusUnauthorized || e.Status == http.StatusForbidden
}

// ContractMismatch reports that the far side refused the version Maven speaks.
func (e *ecosystemError) ContractMismatch() bool {
	return e.Status == http.StatusNotAcceptable || e.Status == http.StatusUpgradeRequired
}

// Unreachable reports a call that never produced an HTTP answer at all
// (connection refused, timeout, cancelled).
func (e *ecosystemError) Unreachable() bool { return e.Status == 0 }

// httpError builds an ecosystemError from a response status.
func httpError(service, op string, status int) *ecosystemError {
	return &ecosystemError{
		Service: service, Op: op, Status: status,
		Err: errors.New(http.StatusText(status)),
	}
}

// hexisStatusTexts maps the http.StatusText spelling back to its code, for the
// failure statuses a Hexis call can plausibly answer with. It is the inverse of
// what the vendored client threw away.
var hexisStatusTexts = func() map[string]int {
	codes := []int{
		http.StatusBadRequest, http.StatusUnauthorized, http.StatusForbidden,
		http.StatusNotFound, http.StatusMethodNotAllowed, http.StatusNotAcceptable,
		http.StatusRequestTimeout, http.StatusConflict, http.StatusGone,
		http.StatusUnprocessableEntity, http.StatusUpgradeRequired,
		http.StatusTooManyRequests, http.StatusInternalServerError,
		http.StatusNotImplemented, http.StatusBadGateway,
		http.StatusServiceUnavailable, http.StatusGatewayTimeout,
	}
	m := make(map[string]int, len(codes))
	for _, c := range codes {
		m[http.StatusText(c)] = c
	}
	return m
}()

// hexisError re-wraps an error from the vendored Hexis client as an
// *ecosystemError, so a Hexis failure classifies the same way a Nexus or Praxis
// one does and ecosystemGap can tell a refused credential from an outage.
//
// This is a boundary adapter and it is not the fix anyone would choose. The
// Hexis client lives in another repository and returns
// fmt.Errorf("%s: %s", http.StatusText(status), body) for every status at or
// above 400, so the status text is the only signal that survives — the correct
// fix is a typed error carrying the code, and Maven cannot land it unilaterally
// (Vikunja #587, docs/plans/20-two-artifacts-and-neither-is-spring.md). Parsing
// here is bounded: the message's first colon-delimited segment is the status
// text verbatim, no status text contains a colon, and anything unrecognised —
// "do request: ...", "create request: ..." — is a transport failure and is left
// at status 0, which is exactly what Unreachable() means.
func hexisError(op string, err error) error {
	if err == nil {
		return nil
	}
	var ee *ecosystemError
	if errors.As(err, &ee) {
		return err
	}
	head, _, _ := strings.Cut(err.Error(), ": ")
	return &ecosystemError{
		Service: "hexis", Op: op, Status: hexisStatusTexts[head], Err: err,
	}
}

type nexusClient struct {
	ecosystemHTTP
}

func newNexusClient(url string) *nexusClient {
	return &nexusClient{newEcosystemHTTP("nexus", "X-Nexus-Version", url)}
}

// withToken sets the bearer token sent on every request. Returns the client so
// wiring reads as one expression.
func (c *nexusClient) withToken(token string) *nexusClient {
	c.token = token
	return c
}

type nexusEntity struct {
	ID          string `json:"id"`
	Type        string `json:"type"`
	DisplayName string `json:"display_name"`
	Key         string `json:"key,omitempty"`
	State       string `json:"state,omitempty"`
}

type nexusCandidate struct {
	EntityID    string  `json:"entity_id"`
	DisplayName string  `json:"display_name"`
	Type        string  `json:"type"`
	Score       float64 `json:"score"`
	Evidence    string  `json:"evidence"`
}

type nexusResolveResult struct {
	Status     string           `json:"status"`
	Entity     *nexusEntity     `json:"entity,omitempty"`
	Score      float64          `json:"score,omitempty"`
	Candidates []nexusCandidate `json:"candidates,omitempty"`

	// Flat fields per ECOSYSTEM-SPEC.md §1.5's documented resolve response
	// shape. Nexus emits both this and the nested Entity above; normalize
	// into Entity in UnmarshalJSON so callers only ever look at one place.
	EntityID    string `json:"entity_id,omitempty"`
	EntityType  string `json:"entity_type,omitempty"`
	DisplayName string `json:"display_name,omitempty"`
}

func (r *nexusResolveResult) UnmarshalJSON(data []byte) error {
	type alias nexusResolveResult
	var a alias
	if err := json.Unmarshal(data, &a); err != nil {
		return err
	}
	*r = nexusResolveResult(a)
	if r.Entity == nil && r.EntityID != "" {
		r.Entity = &nexusEntity{ID: r.EntityID, Type: r.EntityType, DisplayName: r.DisplayName}
	}
	return nil
}

func (c *nexusClient) Resolve(ctx context.Context, query string, types []string) (*nexusResolveResult, error) {
	body := map[string]any{"query": query}
	if len(types) > 0 {
		body["types"] = types
	}

	var result nexusResolveResult
	if err := c.postJSON(ctx, "resolve", "/api/v1/resolve", body, &result); err != nil {
		return nil, err
	}
	return &result, nil
}

func (c *nexusClient) Health(ctx context.Context) error {
	return c.getJSON(ctx, "health", "/health", nil)
}

// praxisClient talks to the Praxis HTTP tools API. Maven must not open Praxis's
// SQLite store directly (ecosystem invariant: no component reads another's DB),
// so attention/changes/lifecycle all go over this HTTP contract against praxisd.
type praxisClient struct {
	ecosystemHTTP
}

func newPraxisClient(url string) *praxisClient {
	return &praxisClient{newEcosystemHTTP("praxis", "X-Praxis-Version", url)}
}

func (c *praxisClient) withToken(token string) *praxisClient {
	c.token = token
	return c
}

// praxisAttention — an attention response in either of the two shapes Praxis
// may send (Vikunja #540).
//
// ECOSYSTEM-SPEC §2.6 says the response carries `degraded: [source_ids]` when a
// source is failed or stale, and that Maven is required to say so rather than
// report all-clear. The deployed Praxis answers with a bare JSON array and no
// envelope at all, so both are decoded here: an array is the items, an object is
// the spec envelope. This lands the Maven half without waiting on the server,
// and the sources read below is what makes the hedge work meanwhile.
type praxisAttention struct {
	Items    []map[string]any
	Degraded []string
}

func (a *praxisAttention) UnmarshalJSON(data []byte) error {
	trimmed := bytes.TrimSpace(data)
	if len(trimmed) > 0 && trimmed[0] == '[' {
		return json.Unmarshal(trimmed, &a.Items)
	}
	var env struct {
		Items    []map[string]any `json:"items"`
		Degraded []string         `json:"degraded"`
	}
	if err := json.Unmarshal(trimmed, &env); err != nil {
		return err
	}
	a.Items, a.Degraded = env.Items, env.Degraded
	return nil
}

func (c *praxisClient) ListAttention(ctx context.Context, limit int) (praxisAttention, error) {
	var out praxisAttention
	err := c.getJSON(ctx, "attention", fmt.Sprintf("/api/v1/tools/attention?limit=%d", limit), &out)
	return out, err
}

// praxisSource — one polled source, as much of it as the hedge needs. The tools
// API does not expose sources, so this decodes the plain `/api/v1/sources` rows.
type praxisSource struct {
	ID       string `json:"id"`
	SourceID string `json:"source_id"`
	Health   string `json:"health"`
}

func (s praxisSource) name() string {
	if s.SourceID != "" {
		return s.SourceID
	}
	return s.ID
}

// UnhealthySources reports which sources cannot be trusted to have reported,
// and how many sources Praxis has at all (Vikunja #540).
//
// Only read when the attention list came back empty, which is the one turn where
// an all-clear is at stake. A source whose health field is absent counts as
// healthy: a Praxis that never reports health would otherwise make every quiet
// turn a hedge, and an unreported field is not evidence of a fault. Everything it
// does report other than "ok" — failed, stale, degraded, unknown — counts as
// cannot-tell, because none of them mean the source has spoken.
func (c *praxisClient) UnhealthySources(ctx context.Context) (bad []string, total int, err error) {
	var out []praxisSource
	if err := c.getJSON(ctx, "sources", "/api/v1/sources", &out); err != nil {
		return nil, 0, err
	}
	for _, s := range out {
		if s.Health != "" && s.Health != "ok" {
			bad = append(bad, s.name())
		}
	}
	return bad, len(out), nil
}

// ListAttentionForEntity is ListAttention scoped to a single canonical Nexus
// entity, so callers already holding a resolved entity_id (e.g. after
// resolveEntityReference) can ask "what needs attention for this entity"
// instead of filtering the unscoped list client-side.
func (c *praxisClient) ListAttentionForEntity(ctx context.Context, entityID string, limit int) (praxisAttention, error) {
	var out praxisAttention
	err := c.getJSON(ctx, "attention_for_entity",
		fmt.Sprintf("/api/v1/tools/attention?limit=%d&entity_id=%s", limit, url.QueryEscape(entityID)), &out)
	return out, err
}

func (c *praxisClient) ListChanges(ctx context.Context, limit int) ([]map[string]any, error) {
	var out []map[string]any
	err := c.getJSON(ctx, "changes", fmt.Sprintf("/api/v1/tools/changes?limit=%d", limit), &out)
	return out, err
}

// praxisItem is the typed shape of a Praxis item, decoded from the tools API's
// itemToMap output (pkg/tools/api.go in the praxis repo). Kept as a distinct
// type from the raw attention/changes maps above so lifecycle callers get
// compile-time field checks instead of map[string]any type assertions.
type praxisItem struct {
	ID          string `json:"id"`
	SourceID    string `json:"source_id"`
	ExternalID  string `json:"external_id"`
	Kind        string `json:"kind"`
	Title       string `json:"title"`
	Body        string `json:"body"`
	State       string `json:"state"`
	Importance  int    `json:"importance"`
	FirstSeenAt string `json:"first_seen_at"`
	LastSeenAt  string `json:"last_seen_at"`
	SurfacedAt  string `json:"surfaced_at"`
	AckedAt     string `json:"acknowledged_at"`
	ResolvedAt  string `json:"resolved_at"`
}

// postItemAction posts {"item_id": id} to a Praxis tools lifecycle endpoint
// and decodes the resulting item. Shared by Surface/Acknowledge/Resolve/Ignore.
func (c *praxisClient) postItemAction(ctx context.Context, op, path, itemID string) (*praxisItem, error) {
	return c.postItem(ctx, op, path, map[string]any{"item_id": itemID})
}

// postItem posts a body to a Praxis lifecycle endpoint and decodes the item.
func (c *praxisClient) postItem(ctx context.Context, op, path string, payload map[string]any) (*praxisItem, error) {
	var out praxisItem
	if err := c.postJSON(ctx, op, path, payload, &out); err != nil {
		return nil, err
	}
	return &out, nil
}

// Surface marks an item read/spoken without acknowledging it (surfaced != acknowledged,
// ECOSYSTEM-SPEC.md §2.3). Callers that read attention aloud must call this, never
// Acknowledge, so "I mentioned it" stays distinguishable from "you told me you saw it".
func (c *praxisClient) Surface(ctx context.Context, itemID string) (*praxisItem, error) {
	return c.postItemAction(ctx, "surface", "/api/v1/tools/surface", itemID)
}

func (c *praxisClient) Acknowledge(ctx context.Context, itemID string) (*praxisItem, error) {
	return c.postItemAction(ctx, "acknowledge", "/api/v1/tools/acknowledge", itemID)
}

func (c *praxisClient) Resolve(ctx context.Context, itemID string) (*praxisItem, error) {
	return c.postItemAction(ctx, "resolve", "/api/v1/tools/resolve", itemID)
}

func (c *praxisClient) Ignore(ctx context.Context, itemID string) (*praxisItem, error) {
	return c.postItemAction(ctx, "ignore", "/api/v1/tools/ignore", itemID)
}

func (c *praxisClient) Pin(ctx context.Context, itemID string, pinned bool) (*praxisItem, error) {
	return c.postItem(ctx, "pin", "/api/v1/tools/pin", map[string]any{"item_id": itemID, "pinned": pinned})
}

func (c *praxisClient) GetItem(ctx context.Context, itemID string) (*praxisItem, error) {
	var out praxisItem
	err := c.getJSON(ctx, "get_item", "/api/v1/tools/items/"+itemID, &out)
	if err != nil {
		return nil, err
	}
	return &out, nil
}

func (c *praxisClient) Search(ctx context.Context, query string, limit int) ([]praxisItem, error) {
	var out []praxisItem
	err := c.getJSON(ctx, "search", fmt.Sprintf("/api/v1/tools/search?q=%s&limit=%d", url.QueryEscape(query), limit), &out)
	return out, err
}

// ecosystemWiring holds the ecosystem service clients.
type ecosystemWiring struct {
	nexus  *nexusClient
	hexis  *hexisclient.Client
	praxis *praxisClient
}

func wireEcosystem(cfg *config.Config) *ecosystemWiring {
	w := &ecosystemWiring{}

	// Nexus identity service
	if cfg.Nexus != nil && cfg.Nexus.URL != "" {
		w.nexus = newNexusClient(cfg.Nexus.URL).withToken(cfg.Nexus.Token)
		log.Printf("ecosystem: nexus at %s", cfg.Nexus.URL)
	} else {
		log.Printf("ecosystem: nexus not configured")
	}

	// Hexis capability service
	if cfg.Hexis != nil && cfg.Hexis.URL != "" {
		w.hexis = hexisclient.New(cfg.Hexis.URL).WithToken(cfg.Hexis.Token)
		log.Printf("ecosystem: hexis at %s", cfg.Hexis.URL)
	} else {
		log.Printf("ecosystem: hexis not configured")
	}

	// Praxis attention service (HTTP tools API — never the DB directly)
	if cfg.Praxis != nil && cfg.Praxis.URL != "" {
		w.praxis = newPraxisClient(cfg.Praxis.URL).withToken(cfg.Praxis.Token)
		log.Printf("ecosystem: praxis at %s", cfg.Praxis.URL)
	} else {
		log.Printf("ecosystem: praxis not configured")
	}

	return w
}

// resolveEntityReference extracts and resolves an entity name from utterance text.
// Returns the canonical entity ID on a confident resolve. On an ambiguous match it
// returns candidate display names so the caller can ask for clarification rather
// than silently guessing (ecosystem invariant: ambiguity blocks mutation).
func (w *ecosystemWiring) resolveEntityReference(ctx context.Context, text string, entityTypes []string) (entityID string, displayName string, ambiguous []string, err error) {
	if w == nil || w.nexus == nil {
		return "", "", nil, nil
	}
	if correlationIDFromCtx(ctx) == "" {
		ctx = withCorrelationID(ctx, newCorrelationID())
	}
	result, err := w.nexus.Resolve(ctx, text, entityTypes)
	if err != nil {
		log.Printf("ecosystem: nexus resolve error: %v", err)
		return "", "", nil, err
	}
	if result.Status == "resolved" {
		// "resolved" with nothing to resolve to is a contract violation, not a
		// miss. Treating it as "no such entity" let the caller fall straight
		// through to the local executor with his verb intact, which is a
		// dependency failure reaching execution.
		if result.Entity == nil || result.Entity.ID == "" {
			err := &ecosystemError{
				Service: "nexus", Op: "resolve", Status: 200,
				Err: errors.New("resolved status with no entity"),
			}
			log.Printf("ecosystem: %v", err)
			return "", "", nil, err
		}
		return result.Entity.ID, result.Entity.DisplayName, nil, nil
	}
	if result.Status == "ambiguous" {
		names := make([]string, 0, len(result.Candidates))
		for _, c := range result.Candidates {
			names = append(names, c.DisplayName)
		}
		log.Printf("ecosystem: ambiguous entity '%s' — %d candidates", text, len(names))
		return "", "", names, nil
	}
	return "", "", nil, nil
}

// discoverCapabilities returns Hexis capabilities applicable to an entity.
// A non-nil error means Hexis could not be reached or refused the request —
// distinct from a nil error with zero capabilities, which means Hexis is
// healthy and genuinely has nothing registered for this entity. Callers must
// not conflate the two: a dependency failure must not silently read as "no
// capabilities" and fall through to unrelated local execution.
//
// The correlation header is stamped in the client's do(), so discovery and
// execution can be joined on the Hexis side as long as both hops carry the
// same ID through ctx. (This used to say the header went out on Execute only;
// that was never true of the vendored code and is not true after the 2026-08-01
// re-vendor.)
func (w *ecosystemWiring) discoverCapabilities(ctx context.Context, entityID string) ([]hexisclient.Capability, error) {
	if w == nil || w.hexis == nil || entityID == "" {
		return nil, nil
	}
	caps, err := w.hexis.Capabilities(ctx, entityID)
	if err != nil {
		err = hexisError("capabilities", err)
		log.Printf("ecosystem: hexis capabilities error: %v", err)
		return nil, err
	}
	return caps, nil
}

// executeCapability runs a Hexis capability, tagging the request with a
// correlation ID so the call is traceable across services. Returns the
// correlation ID alongside the outcome.
func (w *ecosystemWiring) executeCapability(ctx context.Context, capabilityID, targetEntityID string, args map[string]any) (correlationID string, err error) {
	if w == nil || w.hexis == nil {
		return "", fmt.Errorf("hexis not configured")
	}
	correlationID = newCorrelationID()
	ctx = withCorrelationID(ctx, correlationID)
	ctx = hexisclient.WithCorrelationID(ctx, correlationID)
	req := hexisclient.ExecuteRequest{
		CapabilityID:   capabilityID,
		TargetEntityID: targetEntityID,
		Arguments:      args,
		RequestedBy:    map[string]string{"system": "maven", "actor": "user"},
		Origin:         map[string]string{"source": "voice"},
		CorrelationID:  correlationID,
	}

	exec, err := w.hexis.Execute(ctx, req)
	if err != nil {
		// A classified dependency failure. The two returns below are NOT: an
		// execution that ran and failed is the command failing, not Hexis
		// degrading, and it keeps its plain error so the caller says so.
		return correlationID, hexisError("execute", err)
	}
	if exec.Status == "succeeded" {
		return correlationID, nil
	}
	if exec.Error != "" {
		return correlationID, fmt.Errorf("execution failed: %s", exec.Error)
	}
	return correlationID, fmt.Errorf("execution status: %s", exec.Status)
}

// newCorrelationID returns a short unique ID for cross-service call tracing.
func newCorrelationID() string {
	var b [8]byte
	if _, err := rand.Read(b[:]); err != nil {
		return fmt.Sprintf("cor-%d", time.Now().UnixNano())
	}
	return "cor-" + hex.EncodeToString(b[:])
}