// Package httpapi implements the Oikos REST API. The contract is
// api/openapi.yaml (contract-first, ADR-0004); handlers implement the
// oapi-codegen strict-server interface in gen/. Errors map to RFC 9457
// problem+json via domain sentinels.
package httpapi

import (
	"context"
	"crypto/subtle"
	"log/slog"
	"net/http"
	"strings"
	"time"

	"github.com/dtoro/oikos/internal/config"
	"github.com/dtoro/oikos/internal/db"
	"github.com/dtoro/oikos/internal/httpapi/gen"
	"github.com/go-chi/chi/v5"
	"github.com/go-chi/chi/v5/middleware"
)

// Server implements gen.StrictServerInterface over the DB layer.
type Server struct {
	pool *db.Pool
	cfg  config.Config
}

// NewHandler builds the full HTTP handler: /healthz (unauthenticated,
// SG18) + the OpenAPI surface under /api/v1 behind bearer auth.
func NewHandler(pool *db.Pool, cfg config.Config) http.Handler {
	s := &Server{pool: pool, cfg: cfg}

	r := chi.NewRouter()
	r.Use(middleware.Recoverer)
	r.Use(middleware.RequestID)
	r.Use(requestLogger)

	// Liveness — no auth, no audit (plan SG18). Not exposed via Caddy.
	r.Get("/healthz", func(w http.ResponseWriter, req *http.Request) {
		ctx, cancel := context.WithTimeout(req.Context(), 2*time.Second)
		defer cancel()
		if err := pool.Ping(ctx); err != nil {
			writeProblem(w, req, http.StatusServiceUnavailable, "database unreachable", "")
			return
		}
		w.Header().Set("Content-Type", "application/json")
		w.Write([]byte(`{"status":"ok"}`))
	})

	strict := gen.NewStrictHandlerWithOptions(s, nil, gen.StrictHTTPServerOptions{
		RequestErrorHandlerFunc: func(w http.ResponseWriter, req *http.Request, err error) {
			writeProblem(w, req, http.StatusBadRequest, "bad request", err.Error())
		},
		ResponseErrorHandlerFunc: writeProblemFromErr,
	})

	gen.HandlerWithOptions(strict, gen.ChiServerOptions{
		BaseURL:     "/api/v1",
		BaseRouter:  r,
		Middlewares: []gen.MiddlewareFunc{bearerAuth(cfg)},
		ErrorHandlerFunc: func(w http.ResponseWriter, req *http.Request, err error) {
			writeProblem(w, req, http.StatusBadRequest, "bad request", err.Error())
		},
	})

	return r
}

// bearerAuth is the interim Phase 2 auth: a static bearer token
// (OIKOS_API_TOKEN / OIKOS_MCP_BEARER_TOKEN from Infisical in prod). In
// dev mode with no token configured, requests pass as the operator.
// Authentik OIDC JWT validation (operator/viewer scopes) lands later in
// Phase 2 — tracked in the plan's AuthN/AuthZ table.
func bearerAuth(cfg config.Config) func(http.Handler) http.Handler {
	tokens := [][]byte{}
	if cfg.APIToken != "" {
		tokens = append(tokens, []byte(cfg.APIToken))
	}
	if cfg.MCPBearerToken != "" {
		tokens = append(tokens, []byte(cfg.MCPBearerToken))
	}
	devOpen := cfg.APIEnv == "dev" && len(tokens) == 0

	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			if devOpen {
				next.ServeHTTP(w, r)
				return
			}
			auth := r.Header.Get("Authorization")
			raw, ok := strings.CutPrefix(auth, "Bearer ")
			if ok {
				for _, t := range tokens {
					if subtle.ConstantTimeCompare([]byte(raw), t) == 1 {
						next.ServeHTTP(w, r)
						return
					}
				}
			}
			writeProblem(w, r, http.StatusUnauthorized, "unauthorized",
				"missing or invalid bearer token")
		})
	}
}

// requestLogger logs one line per request with method, path, status,
// duration, and the chi request id.
func requestLogger(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		start := time.Now()
		ww := middleware.NewWrapResponseWriter(w, r.ProtoMajor)
		next.ServeHTTP(ww, r)
		slog.Info("http",
			"method", r.Method,
			"path", r.URL.Path,
			"status", ww.Status(),
			"duration_ms", time.Since(start).Milliseconds(),
			"request_id", middleware.GetReqID(r.Context()),
		)
	})
}

// ListenAndServe runs the API server with graceful shutdown on ctx cancel
// (SG4): stop accepting, drain in-flight for up to 30s, then exit.
func ListenAndServe(ctx context.Context, pool *db.Pool, cfg config.Config) error {
	srv := &http.Server{
		Addr:              cfg.APIListen,
		Handler:           NewHandler(pool, cfg),
		ReadHeaderTimeout: 10 * time.Second,
	}

	errCh := make(chan error, 1)
	go func() {
		slog.Info("api listening", "addr", cfg.APIListen)
		errCh <- srv.ListenAndServe()
	}()

	select {
	case err := <-errCh:
		return err
	case <-ctx.Done():
		slog.Info("api shutting down")
		shutdownCtx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
		defer cancel()
		return srv.Shutdown(shutdownCtx)
	}
}