// Package router is where the whole application gets wired together: it
// receives already-constructed shared dependencies (logger, db, sessions,
// config) from main.go, builds the handlers and middleware that need them,
// and registers every route on a chi.Mux.
package router

import (
	"database/sql"
	"log/slog"
	"time"

	"github.com/alexedwards/scs/v2"
	"github.com/go-chi/chi/v5"
	chimw "github.com/go-chi/chi/v5/middleware"
	"github.com/go-chi/cors"
	"github.com/go-chi/httprate"

	"git.hamidsoltani.com/hamid/go-simple-api/internal/config"
	"git.hamidsoltani.com/hamid/go-simple-api/internal/handlers"
	"git.hamidsoltani.com/hamid/go-simple-api/internal/middleware"
	"git.hamidsoltani.com/hamid/go-simple-api/internal/models"
	"git.hamidsoltani.com/hamid/go-simple-api/internal/oauth"
)

// New builds and returns the fully configured chi router for the
// application. *chi.Mux implements http.Handler (it has a ServeHTTP
// method), so the return value can be passed directly to http.Server as
// its Handler - see cmd/api/main.go.
func New(logger *slog.Logger, db *sql.DB, sessions *scs.SessionManager, cfg config.Config) *chi.Mux {
	r := chi.NewRouter()

	// --- Global middleware stack ---
	// Order matters here: each middleware wraps everything registered
	// after it, so requests flow through this list top-to-bottom on the
	// way in, and bottom-to-top on the way out.

	// Tags every request with a unique ID, retrievable later via
	// chimw.GetReqID(ctx) - used by our RequestLogger below, and useful
	// for correlating log lines to one specific request once shipped to
	// Loki.
	r.Use(chimw.RequestID)

	// Our own structured JSON request logger (internal/middleware),
	// replacing chi's built-in plain-text Logger.
	r.Use(middleware.RequestLogger(logger))

	// Recovers from panics in any handler, returning a 500 instead of
	// crashing the whole server process for one bad request.
	r.Use(chimw.Recoverer)

	// Cancels a request's context if it runs longer than this, so a slow
	// downstream call (e.g. a hung database query) can't hold a
	// connection open forever.
	r.Use(chimw.Timeout(60 * time.Second))

	// CORS: controls which browser-based frontends (running on a
	// different origin than this API) are allowed to call it with
	// credentials (cookies) attached. This does NOT protect against
	// non-browser callers (curl, mobile apps, server-to-server) - CORS is
	// a browser-enforced rule, not a server-side security boundary.
	r.Use(cors.Handler(cors.Options{
		AllowedOrigins:   cfg.AllowedOrigins,
		AllowedMethods:   []string{"GET", "POST", "PUT", "DELETE"},
		AllowedHeaders:   []string{"Content-Type"},
		AllowCredentials: true, // required for the session cookie to be sent cross-origin
	}))

	// A generous, global rate limit - mostly a safety net against
	// runaway scripts/bots hitting the API in general. 100 requests per
	// IP per minute.
	r.Use(httprate.LimitByIP(100, time.Minute))

	// scs's own middleware: loads session data (from Redis) into the
	// request's context before the handler runs, and saves any changes
	// back (plus sets/refreshes the cookie) after the handler finishes.
	// Every route below this line can use sessions.Get/Put/Destroy.
	r.Use(sessions.LoadAndSave)

	// --- Public routes ---

	r.Get("/health", handlers.Health)

	userRepo := models.NewUserRepository(db)
	authHandler := handlers.NewAuthHandler(userRepo, sessions, logger)
	requireAuth := middleware.RequireAuth(sessions, userRepo, logger)

	// Register/Login get a MUCH stricter rate limit than the global one,
	// since these are exactly the endpoints a credential-stuffing /
	// brute-force script would target: 5 requests per IP per minute.
	// r.Group scopes this middleware to only the routes registered inside
	// the closure - it does not affect any route registered outside it.
	r.Group(func(r chi.Router) {
		r.Use(httprate.LimitByIP(5, time.Minute))
		r.Post("/register", authHandler.Register)
		r.Post("/login", authHandler.Login)
	})

	// Deliberately OUTSIDE the strict-rate-limit group above - we don't
	// want to rate-limit a legitimate logged-in user trying to log out.
	r.Post("/logout", authHandler.Logout)

	// --- Protected routes ---
	// Every route registered inside this group first passes through
	// requireAuth; if the caller isn't authenticated, requireAuth responds
	// 401 and the route handler never runs at all. Add future
	// authenticated-only routes inside this same group.
	r.Group(func(r chi.Router) {
		r.Use(requireAuth)
		r.Get("/me", authHandler.Me)
	})

	// --- Google OAuth2 routes ---

	googleConfig := oauth.NewGoogleConfig(cfg)
	googleHandler := handlers.NewGoogleOAuthHandler(googleConfig, userRepo, sessions, logger)

	r.Get("/auth/google/login", googleHandler.Login)
	r.Get("/auth/google/callback", googleHandler.Callback)

	return r
}