// Package server provides the HTTP API for the foreman daemon.
//
// Why: foreman exposes a native Ollama-compatible API plus async job endpoints;
// centralizing routing and middleware here keeps cmd/foreman thin.
// What: creates a stdlib net/http server with health checks, optional bearer-token
// auth, and an extensible mux for later phases.
// Test: start the server with httptest, hit /healthz, verify 200; set a token,
// verify 401 without it.
package server

import (
	"encoding/json"
	"log/slog"
	"net/http"
	"strings"

	"gitea.stevedudenhoeffer.com/steve/foreman/internal/config"
	"gitea.stevedudenhoeffer.com/steve/foreman/internal/store"
)

// Server holds the HTTP server and its dependencies.
type Server struct {
	cfg    config.Config
	store  *store.Store
	mux    *http.ServeMux
	logger *slog.Logger
}

// New creates a new Server with the given configuration and store. The mux is
// populated with initial routes; callers can add more before calling ListenAndServe.
//
// Why: dependency injection makes the server testable and extensible.
// What: wires config, store, and logger into the server, registers routes.
// Test: create with New, use httptest to exercise routes.
func New(cfg config.Config, st *store.Store, logger *slog.Logger) *Server {
	s := &Server{
		cfg:    cfg,
		store:  st,
		mux:    http.NewServeMux(),
		logger: logger,
	}
	s.routes()
	return s
}

// Handler returns the server's http.Handler, with auth middleware applied.
//
// Why: allows httptest usage in tests without starting a real listener.
// What: wraps the mux with optional bearer-token middleware.
// Test: call Handler(), use httptest.NewServer, exercise endpoints.
func (s *Server) Handler() http.Handler {
	var h http.Handler = s.mux
	if s.cfg.Token != "" {
		h = s.authMiddleware(h)
	}
	return h
}

// ListenAndServe starts the HTTP server on the configured address.
func (s *Server) ListenAndServe() error {
	s.logger.Info("starting server", "addr", s.cfg.Addr)
	return http.ListenAndServe(s.cfg.Addr, s.Handler())
}

// routes registers all HTTP routes on the mux.
func (s *Server) routes() {
	s.mux.HandleFunc("GET /healthz", s.handleHealthz)
}

// healthResponse is the JSON shape returned by /healthz.
type healthResponse struct {
	Status   string `json:"status"`
	Degraded bool   `json:"degraded"`
}

// handleHealthz returns the daemon's health status. The degraded flag is a
// placeholder for the model poller's connectivity state (Phase 2).
func (s *Server) handleHealthz(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusOK)
	json.NewEncoder(w).Encode(healthResponse{
		Status:   "ok",
		Degraded: false,
	})
}

// authMiddleware validates the Authorization: Bearer <token> header on all
// requests except /healthz. Returns 401 if the token is missing or wrong.
func (s *Server) authMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// /healthz is always public so load balancers and probes work without auth.
		if r.URL.Path == "/healthz" {
			next.ServeHTTP(w, r)
			return
		}

		auth := r.Header.Get("Authorization")
		if auth == "" {
			http.Error(w, `{"error":"missing authorization header"}`, http.StatusUnauthorized)
			return
		}

		const prefix = "Bearer "
		if !strings.HasPrefix(auth, prefix) {
			http.Error(w, `{"error":"invalid authorization header"}`, http.StatusUnauthorized)
			return
		}

		token := strings.TrimPrefix(auth, prefix)
		if token != s.cfg.Token {
			http.Error(w, `{"error":"invalid token"}`, http.StatusUnauthorized)
			return
		}

		next.ServeHTTP(w, r)
	})
}