package main

import (
	"errors"
	"fmt"
	"net/http"

	chassisauth "git.d-ma.be/mathias/mcp-chassis/auth"

	"github.com/mathiasbq/hyperguild/ingestion/internal/api"
	"github.com/mathiasbq/hyperguild/ingestion/internal/metrics"
)

// publicRoutes is the complete set of patterns a caller may register on the
// outer mux, outside the REST API's auth (hyperguild#149). Each authenticates
// itself or is meant to be open: /capture (bearer/JWT), the webhook (HMAC),
// /oauth/token (client secret) and OAuth metadata (open). /mcp and /metrics
// are not here: buildMux builds them itself (hyperguild#154). A REST pattern
// added here would beat the authenticated catch-all by specificity and ship
// open, which is why buildMux refuses anything else.
var publicRoutes = map[string]bool{
	"POST /capture":             true,
	"POST /webhooks/brain-sync": true,
	"GET /.well-known/oauth-protected-resource":   true,
	"GET /.well-known/oauth-authorization-server": true,
	"POST /oauth/token":                           true,
}

// restAuth is the credential the REST API checks: the same as /mcp's.
type restAuth struct {
	token               string
	validator           *chassisauth.JWTValidator
	realm               string
	resourceMetadataURL string
}

// buildMux builds the handler main passes to ListenAndServe unchanged. The
// REST API is mounted at "/" and /mcp is registered, both behind bearer auth
// that buildMux constructs itself from auth (one credential), so a caller
// cannot pass a no-op. GET /metrics serves reg, and the whole router is
// wrapped in reg's middleware. Other public handlers are registered as given,
// and only for patterns on the publicRoutes allowlist. It returns an
// http.Handler, not the *ServeMux, so nothing can register a route on the
// result. What stays untested is main's own line: a handler main built around
// this one before ListenAndServe would not be seen by these tests.
func buildMux(
	auth restAuth, h *api.Handler, mcpHandler http.Handler, reg *metrics.Registry, public map[string]http.Handler,
) (http.Handler, error) {
	if auth.token == "" {
		return nil, errors.New("buildMux: REST auth needs a token")
	}
	if mcpHandler == nil || reg == nil {
		return nil, errors.New("buildMux: needs the MCP handler and the metrics registry")
	}
	mux := http.NewServeMux()
	for pattern, handler := range public {
		if !publicRoutes[pattern] {
			return nil, fmt.Errorf("buildMux: %q is not an allowed public route", pattern)
		}
		mux.Handle(pattern, handler)
	}
	bearer := func(next http.Handler) http.Handler {
		return chassisauth.BearerMiddleware(auth.token, auth.validator, auth.realm, auth.resourceMetadataURL, next)
	}
	mux.Handle("/mcp", bearer(mcpHandler))
	// /metrics is registered on the mux and so observed by its own
	// middleware, like any route.
	mux.Handle("GET /metrics", reg.Handler())
	mountREST(mux, h, bearer)
	return reg.Middleware(mux), nil
}

// mountREST registers the REST API on its own mux and mounts it at "/" behind
// auth: anything not registered as public lands here and is authenticated,
// including routes added later.
func mountREST(mux *http.ServeMux, h *api.Handler, auth func(http.Handler) http.Handler) {
	rest := http.NewServeMux()
	rest.HandleFunc("POST /query", h.Query)
	rest.HandleFunc("POST /write", h.Write)
	rest.HandleFunc("POST /index", h.Index)
	rest.HandleFunc("POST /ingest", h.Ingest)
	rest.HandleFunc("POST /ingest-path", h.IngestPath)
	rest.HandleFunc("POST /ingest-raw", h.IngestRaw)
	rest.HandleFunc("POST /backfill-refs", h.BackfillRefs)
	rest.HandleFunc("GET /pending", h.Pending)
	rest.HandleFunc("POST /promote", h.Promote)
	rest.HandleFunc("POST /backfill-embeddings", h.BackfillEmbeddings)
	rest.HandleFunc("GET /pass-rate", h.PassRate)
	mux.Handle("/", labelRESTPattern(rest, auth(rest)))
}

// labelRESTPattern sets the request's Pattern to the REST route it addresses
// before auth runs, so the metrics middleware (which reads Pattern from the
// same *http.Request) labels a refused request by its route rather than by
// the "/" mount (hyperguild#155). A refused request to a path no route
// matches keeps "/", so for refused requests the label set stays bounded by
// the registered routes. That bound does not hold for authenticated
// requests: an unregistered path reaches the REST mux, which 404s with an
// empty Pattern, and the metrics middleware falls back to the raw URL path
// (hyperguild#185).
func labelRESTPattern(rest *http.ServeMux, next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if _, pattern := rest.Handler(r); pattern != "" {
			r.Pattern = pattern
		}
		next.ServeHTTP(w, r)
	})
}