/*
catcrafts.net
Copyright (C) 2026 Catcrafts

The source code of this website is made available for viewing purposes only.
No permission is granted to copy, modify, distribute, or create derivative works.
*/

// The native server: server-rendered pages, order storage, and the bunq
// payment rail.
//
// Unlike Catcrafts.Shared this module is host-only and may import whatever it
// needs — Crafter.Network here, OpenSSL for request signing. The division of
// labour is that Shared decides what the markup IS and Server decides how it
// reaches a socket, where orders live, and how money moves.

export module Catcrafts.Server;
import std;
import Catcrafts.Shared;

export namespace Catcrafts::Server {

    // Parse content/*.json and lift the wasm bundle's <script> tags.
    //
    // `bundleIndexHtml` is the generated index.html from the wasm build; the
    // script tags are extracted from it verbatim because they carry a
    // ?v=<buildId> cache buster that changes every build. Pass an empty path to
    // serve no wasm at all (every page then renders as plain HTML).
    //
    // Call before Serve. Content is immutable afterwards: it is generated at
    // build time, so nothing can change it under a running process.
    void LoadContent(const std::filesystem::path& contentDir,
                     const std::filesystem::path& bundleIndexHtml);

    std::size_t ContentPostCount();
    std::size_t ContentProjectCount();
    std::size_t ContentProductCount();

    // ── orders ────────────────────────────────────────────────────────
    //
    // An append-only JSON-lines EVENT LOG, not a database. Two event types:
    // "order" (the full record, written once) and "status" (a transition).
    // Current state is a fold over the file — later events win. Nothing is
    // ever rewritten in place, so the file is also the audit trail, and a
    // crash mid-append costs at most the line being written.
    //
    // The volume argument: this sells single-digit units per week. When that
    // is wrong by two orders of magnitude, the log imports into SQLite in one
    // sitting — the reverse migration would not be so kind.

    struct OrderRecord {
        std::string token;          // 32-hex capability; the /order/<token> URL
        std::string reference;      // "CC-XXXXXX", quoted in bank transfers
        std::string product;        // product slug
        std::string color;          // variant slug ("green"), empty pre-variants
        std::int64_t quantity = 1;
        std::int64_t unitMinor = 0; // per-unit gross at order time — prices
                                    // change; the record must not
        std::string createdAt;      // ISO 8601 UTC
        std::string updatedAt;      // of the newest event folded in
        Form::Checkout buyer;
        std::int64_t goodsMinor = 0;
        std::int64_t shippingMinor = 0;
        std::int64_t totalMinor = 0;
        bool vatIncluded = false;
        std::string status = "awaiting_payment";  // -> paid -> shipped | cancelled
        std::string payUrl;          // the provider's hosted checkout link
        std::string payId;           // provider payment id ("tr_…" at Mollie)
        std::string paidVia;         // method that settled it ("ideal", "creditcard")
        std::string invoiceNumber;   // "<customer-uuid>-<n>", set at paid
        std::string invoicedAt;      // ISO 8601 of the invoice event
    };

    void SetOrdersPath(const std::filesystem::path& path);
    bool CreateOrder(const OrderRecord& order);
    // Appends a status event. Never mutates prior lines; the fold applies it.
    // `via` records HOW a payment settled ("ideal", "creditcard") on the paid
    // transition — card money stays reversible for months, so the ledger must
    // show at a glance which orders carry that tail risk.
    bool AppendOrderStatus(std::string_view token, std::string_view status,
                           std::string_view isoTimestamp,
                           std::string_view via = {});
    std::optional<OrderRecord> FindOrder(std::string_view token);
    std::vector<OrderRecord> ListOrders();

    // Assigns the next invoice number in the CUSTOMER's series and appends
    // the invoice event. The scheme continues the owner's pre-shop
    // administration: customer number is a random UUID, invoices count
    // sequentially within it ("f57c6512-…-3"). Art. 226(2) permits "one or
    // more series"; per-customer is the established practice here, and the
    // ledger + payment-provider records carry the completeness proof.
    // Idempotent: an order that already has a number keeps it. Fold and
    // append happen under one lock, so two paid transitions cannot race the
    // same number.
    std::optional<std::string> AssignInvoiceNumber(std::string_view token,
                                                   std::string_view isoTimestamp);

    // ── invoices ──────────────────────────────────────────────────────
    //
    // A paid order's invoice: plain markdown, clearsigned with the shop's
    // GPG key so its authenticity outlives this server. The page invites the
    // buyer to download it rather than promising to host receipts forever.

    // Pure and exported for the self-test: everything on a Dutch invoice —
    // seller identity (KVK/VAT), sequential number, dates, buyer address,
    // per-line amounts, VAT treatment for EU and export.
    std::string BuildInvoiceMarkdown(const OrderRecord& order,
                                     std::string_view productName,
                                     std::string_view colorLabel);

    // The GPG key (uid or fingerprint) invoices are clearsigned with; empty
    // disables signing and invoices carry an UNSIGNED marker instead —
    // honest in dev, wrong in production.
    void ConfigureInvoicing(std::string gpgKeyId);

    // Clearsign via the gpg binary (GNUPGHOME decides the keyring). nullopt
    // when signing is configured but fails — the caller must NOT serve an
    // unsigned invoice in that case.
    std::optional<std::string> ClearsignInvoice(const std::string& markdown);
    bool InvoiceSigningConfigured();

    // 128 bits of CSPRNG entropy as 32 lowercase hex — the whole capability to
    // read one order. And its human-sized companion, derived (not random) so a
    // record can never carry a mismatched pair.
    std::string NewOrderToken();
    std::string ReferenceFromToken(std::string_view token);

    // ── payments ──────────────────────────────────────────────────────
    //
    // A rail turns "this order wants €X" into a URL a buyer can pay at, and
    // answers "has it been paid?". Everything else — storage, rendering,
    // reconciling — is rail-agnostic, which is what will let a crypto rail
    // slot in later without reshaping orders.

    struct PaymentLink {
        std::string payUrl;
        std::string payId;
    };

    // What a poll learned about one payment. Pending and Dead are different
    // answers on purpose: a Mollie payment EXPIRES (unlike a bunq tab), and an
    // order whose payment can never arrive should lapse rather than sit
    // "awaiting" forever.
    enum class PayState { Pending, Paid, Dead };
    struct PaidStatus {
        PayState state = PayState::Pending;
        std::string method;   // "ideal" | "creditcard" | "banktransfer" | …
    };

    class PaymentRail {
    public:
        virtual ~PaymentRail() = default;
        // nullopt = the provider could not be reached / refused. The checkout
        // surfaces that honestly instead of creating an unpayable order.
        virtual std::optional<PaymentLink> CreateLink(std::int64_t amountMinor,
                                                      const std::string& description,
                                                      const std::string& redirectUrl) = 0;
        // nullopt = could not determine (network, auth) — retry later. Never
        // guess Dead from a transport error: only the provider saying
        // expired/canceled/failed kills an order.
        virtual std::optional<PaidStatus> CheckPaid(const std::string& payId,
                                                    std::int64_t expectedMinor) = 0;
        virtual std::string_view Name() const = 0;
        // How often the reconciler sweeps. The fake rail returns something
        // tiny so tests are fast; the real providers get a respectful cadence.
        virtual std::chrono::seconds PollInterval() const = 0;
    };

    struct RailConfig {
        std::string mode;                 // "off" | "fake" | "mollie" | "bunq"
        std::string apiKey;               // mollie: live_… or test_…; bunq: its key
        bool sandbox = false;             // bunq only: public-api.sandbox.bunq.com
        std::filesystem::path statePath;  // bunq: session context; fake: paid marker
        std::string redirectBase = "https://catcrafts.net";
    };

    // nullptr for mode "off" — the shop then renders but refuses checkout.
    std::unique_ptr<PaymentRail> MakeRail(const RailConfig& config);

    // Parsed essentials of a Mollie /v2/payments object. Exported so the
    // self-test can drive the parser with canned responses — the HTTP around
    // it is thin.
    struct MolliePayment {
        std::string id;
        std::string status;       // open|pending|authorized|paid|canceled|expired|failed
        std::string method;       // may be empty until the payer picks one
        std::string checkoutUrl;  // present while payable
        std::int64_t amountMinor = 0;
    };
    std::optional<MolliePayment> ParseMolliePayment(std::string_view json);

    // Exact decimal-string-to-minor-units parser for amounts coming back from
    // the bunq API ("614.00" -> 61400). Rejects anything that is not a plain
    // non-negative decimal with at most two fraction digits — no floats touch
    // money on the way in either. Exported for the self-test.
    std::optional<std::int64_t> ParseAmountToMinor(std::string_view s);

    // ── shipping rates ────────────────────────────────────────────────
    //
    // Live per-country rates from Sendcloud's shipping_methods API, cached to
    // a state file and refreshed daily by a background thread. The compiled-in
    // zone table (Catcrafts.Shared:Content) remains the fallback for any country the carrier table
    // does not cover — and the whole feature when no credentials exist, so
    // the shop never depends on Sendcloud being up.

    struct ShippingConfig {
        std::string publicKey;            // SENDCLOUD_PUBLIC_KEY
        std::string secretKey;            // SENDCLOUD_SECRET_KEY
        std::string methodName;           // substring match on the method name
        std::filesystem::path cachePath;  // survives restarts
    };

    // Country -> price in cents, EUR. Empty when nothing loaded.
    struct ShippingTable {
        std::string method;               // the matched Sendcloud method name
        std::string fetchedAt;            // ISO 8601, for the operator
        std::vector<std::pair<std::string, std::int64_t>> perCountry;

        std::int64_t Find(std::string_view cc) const {
            for (const auto& [k, v] : perCountry) {
                if (k == cc) return v;
            }
            return 0;
        }
    };

    // Parse a Sendcloud /api/v2/shipping_methods response into a table, taking
    // the first method whose name contains `methodName` (case-sensitive).
    // Exported for the self-test — the network fetch is thin around this.
    ShippingTable ParseSendcloudMethods(std::string_view json, std::string_view methodName);

    // Install the config and start using it. Safe to skip entirely.
    void ConfigureShipping(const ShippingConfig& config);

    // One fetch attempt; failure leaves the previous table standing. The HTTP
    // layer's background thread calls this on start and daily after.
    void RefreshShippingTable();

    // The rate the checkout charges for `country`: the live table's price if
    // present, the product's zone fallback otherwise.
    std::int64_t ShipCostFor(std::string_view country, std::int64_t zoneNl,
                             std::int64_t zoneEu, std::int64_t zoneWorld);

    // A snapshot of the live table for embedding into the checkout preview —
    // the page must show the same numbers the server will charge.
    ShippingTable CurrentShippingTable();

    // Install the rail used by Serve()'s checkout handler and reconciler.
    // Call before Serve. Passing nullptr disables checkout. (Rates travel with
    // the content — LoadContent reads rates.json.)
    void ConfigurePayments(std::unique_ptr<PaymentRail> rail, std::string redirectBase);

    // Bind and serve until killed. Blocks. Starts the payment reconciler
    // thread when a rail is configured.
    //
    // Plaintext HTTP/1.1 by design: Caddy terminates TLS and reverse-proxies to
    // localhost. Do not expose this port directly.
    int Serve(std::uint16_t port);
}