email_agent/internal/server/server.go

// Package server wires the HTTP surface of the Email Agent.
//
// Phase 1.2 exposes a session login and an empty HTMX dashboard shell in the
// Family Home Lab design system. Mail fetch arrives in Phase 2.
package server

import (
	"context"
	"crypto/rand"
	"encoding/json"
	"errors"
	"fmt"
	"html/template"
	"io/fs"
	"log/slog"
	"mime"
	"net/http"
	"time"

	"gitea.lab.audasmedia.com.au/sam/email_agent/internal/config"
	"gitea.lab.audasmedia.com.au/sam/email_agent/internal/mailfetch"
	"gitea.lab.audasmedia.com.au/sam/email_agent/internal/session"
	"gitea.lab.audasmedia.com.au/sam/email_agent/internal/store"
	"gitea.lab.audasmedia.com.au/sam/email_agent/internal/version"
	"gitea.lab.audasmedia.com.au/sam/email_agent/web"
)

func init() {
	// Go's mime table has no woff2 entry; the self-hosted Inter fonts need it.
	_ = mime.AddExtensionType(".woff2", "font/woff2")
}

// Server holds the HTTP dependencies.
type Server struct {
	cfg      *config.Config
	store    *store.Store
	logger   *slog.Logger
	http     *http.Server
	tmpl     *template.Template
	sessions *session.Manager
	fetcher  *mailfetch.Fetcher
}

// New builds a Server. It does not start listening.
func New(cfg *config.Config, st *store.Store, logger *slog.Logger) (*Server, error) {
	tmpl, err := template.ParseFS(web.TemplateFS, "templates/*.html")
	if err != nil {
		return nil, fmt.Errorf("parse templates: %w", err)
	}

	key, err := sessionKey(cfg, logger)
	if err != nil {
		return nil, fmt.Errorf("session key: %w", err)
	}
	sessions, err := session.NewManager(key, session.DefaultTTL)
	if err != nil {
		return nil, fmt.Errorf("session manager: %w", err)
	}

	s := &Server{
		cfg:      cfg,
		store:    st,
		logger:   logger,
		tmpl:     tmpl,
		sessions: sessions,
		fetcher:  mailfetch.NewFetcher(cfg, st, logger),
	}
	s.http = &http.Server{
		Addr:              cfg.Addr,
		Handler:           s.Handler(),
		ReadHeaderTimeout: 10 * time.Second,
		ReadTimeout:       30 * time.Second,
		WriteTimeout:      30 * time.Second,
		IdleTimeout:       60 * time.Second,
	}
	return s, nil
}

// sessionKey returns the cookie signing key. In production it comes from
// EMAIL_AGENT_SESSION_SECRET; with no secret configured the service still
// starts with an ephemeral key so it is usable, but sessions do not survive a
// restart and the operator sees a warning.
func sessionKey(cfg *config.Config, logger *slog.Logger) ([]byte, error) {
	if cfg.SessionSecret != "" {
		return []byte(cfg.SessionSecret), nil
	}
	key := make([]byte, 32)
	if _, err := rand.Read(key); err != nil {
		return nil, err
	}
	logger.Warn("EMAIL_AGENT_SESSION_SECRET is not set; using an ephemeral session key (sessions reset on restart)")
	return key, nil
}

// Handler returns the root HTTP handler with middleware applied.
func (s *Server) Handler() http.Handler {
	staticFS, err := fs.Sub(web.StaticFS, "static")
	if err != nil {
		// web.StaticFS is a compile-time constant; this cannot fail at runtime.
		panic(fmt.Sprintf("static assets: %v", err))
	}
	static := http.StripPrefix("/static/", http.FileServer(http.FS(staticFS)))

	mux := http.NewServeMux()
	mux.HandleFunc("GET /health", s.handleHealth)
	mux.HandleFunc("GET /readyz", s.handleReady)
	mux.Handle("GET /static/", static)

	mux.HandleFunc("GET /login", s.handleLoginGet)
	mux.HandleFunc("POST /login", s.handleLoginPost)
	mux.HandleFunc("POST /logout", s.handleLogout)

	mux.HandleFunc("GET /{$}", s.requireAuth(s.handleDashboard))
	mux.HandleFunc("GET /partials/inbox", s.requireAuth(s.handleInboxPartial))
	mux.HandleFunc("POST /actions/fetch", s.requireAuth(s.handleFetchMail))

	return s.recoverPanic(s.logRequests(mux))
}

// Run starts the HTTP server and blocks until ctx is cancelled.
func (s *Server) Run(ctx context.Context) error {
	errCh := make(chan error, 1)
	go func() {
		s.logger.Info("http server listening",
			"addr", s.cfg.Addr,
			"env", s.cfg.Env,
			"db", s.store.Path(),
			"version", version.Version,
		)
		if err := s.http.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
			errCh <- err
			return
		}
		errCh <- nil
	}()

	select {
	case err := <-errCh:
		return err
	case <-ctx.Done():
		shutdownCtx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
		defer cancel()
		s.logger.Info("shutting down http server")
		return s.http.Shutdown(shutdownCtx)
	}
}

type healthResponse struct {
	Status        string `json:"status"`
	Version       string `json:"version"`
	Commit        string `json:"commit"`
	Env           string `json:"env"`
	UptimeSeconds int64  `json:"uptime_seconds"`
	Database      string `json:"database"`
	Time          string `json:"time"`
}

var startedAt = time.Now()

// handleHealth reports liveness plus a database connectivity check.
func (s *Server) handleHealth(w http.ResponseWriter, r *http.Request) {
	ctx, cancel := context.WithTimeout(r.Context(), 2*time.Second)
	defer cancel()

	resp := healthResponse{
		Status:        "ok",
		Version:       version.Version,
		Commit:        version.Commit,
		Env:           s.cfg.Env,
		UptimeSeconds: int64(time.Since(startedAt).Seconds()),
		Database:      "ok",
		Time:          time.Now().UTC().Format(time.RFC3339),
	}
	code := http.StatusOK

	if err := s.store.Ping(ctx); err != nil {
		s.logger.Error("health check: database unreachable", "error", err)
		resp.Status = "degraded"
		resp.Database = "unreachable"
		code = http.StatusServiceUnavailable
	}

	writeJSON(w, code, resp)
}

// handleReady reports readiness for load balancers (same signal as health).
func (s *Server) handleReady(w http.ResponseWriter, r *http.Request) {
	ctx, cancel := context.WithTimeout(r.Context(), 2*time.Second)
	defer cancel()
	if err := s.store.Ping(ctx); err != nil {
		writeJSON(w, http.StatusServiceUnavailable, map[string]string{"status": "not ready"})
		return
	}
	writeJSON(w, http.StatusOK, map[string]string{"status": "ready"})
}

func writeJSON(w http.ResponseWriter, code int, v any) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(code)
	_ = json.NewEncoder(w).Encode(v)
}

// logRequests logs one line per request at debug level.
func (s *Server) logRequests(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		start := time.Now()
		rec := &statusRecorder{ResponseWriter: w, status: http.StatusOK}
		next.ServeHTTP(rec, r)
		s.logger.Debug("request",
			"method", r.Method,
			"path", r.URL.Path,
			"status", rec.status,
			"duration_ms", time.Since(start).Milliseconds(),
			"remote", r.RemoteAddr,
		)
	})
}

// recoverPanic keeps one bad request from taking down the process.
func (s *Server) recoverPanic(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		defer func() {
			if rec := recover(); rec != nil {
				s.logger.Error("panic recovered", "error", rec, "path", r.URL.Path)
				http.Error(w, "internal server error", http.StatusInternalServerError)
			}
		}()
		next.ServeHTTP(w, r)
	})
}

type statusRecorder struct {
	http.ResponseWriter
	status int
}

func (r *statusRecorder) WriteHeader(code int) {
	r.status = code
	r.ResponseWriter.WriteHeader(code)
}