/*
Crafter®.Network
Copyright (C) 2026 Catcrafts®
Catcrafts.net

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 3.0 of the License, or (at your option) any later version.
*/

// JS bridge for the CRAFTER_NETWORK_BROWSER build of Crafter.Network.
// Populates `window.crafter_webbuild_env` with the env imports the .wasm
// declares (crafterNetworkFetch, crafterNetworkWt*), and drives the
// reader loops that feed responses back into the wasm exports
// (CrafterNetworkOnFetchComplete, CrafterNetworkOnWt*).
//
// Crafter.Build's wasi-browser runtime merges this object into the
// WebAssembly import object as the `env` module before instantiation —
// mirrors additional/dom-env.js in Crafter.Graphics.

const __decoder = new TextDecoder();
const __encoder = new TextEncoder();

function __wasm()   { return window.crafter_webbuild_wasi.instance.exports; }
function __memBuf() { return window.crafter_webbuild_wasi.instance.exports.memory.buffer; }

function __readUtf8(ptr, len) {
    return __decoder.decode(new Uint8Array(__memBuf(), ptr, len));
}
function __readBytes(ptr, len) {
    // Copy out of the linear memory — the underlying buffer is detached
    // whenever wasm grows its memory, so handing the view straight back
    // to fetch / WebTransport would risk operating on a freed view.
    return new Uint8Array(__memBuf(), ptr, len).slice();
}
function __allocCopy(bytes) {
    const ptr = __wasm().WasmAlloc(bytes.length);
    new Uint8Array(__memBuf(), ptr, bytes.length).set(bytes);
    return ptr;
}
function __allocUtf8(str) {
    return __allocCopy(__encoder.encode(str));
}

// ─── fetch() bridge ───────────────────────────────────────────────────

function crafterNetworkFetch(methodPtr, methodLen,
                             urlPtr, urlLen,
                             headersPtr, headersLen,
                             bodyPtr, bodyLen,
                             callbackId) {
    const method = __readUtf8(methodPtr, methodLen);
    const url    = __readUtf8(urlPtr, urlLen);
    const init = { method, headers: {} };

    if (headersLen > 0) {
        const headerStr = __readUtf8(headersPtr, headersLen);
        for (const line of headerStr.split('\n')) {
            const sep = line.indexOf(': ');
            if (sep > 0) init.headers[line.slice(0, sep)] = line.slice(sep + 2);
        }
    }
    if (bodyLen > 0 && method !== 'GET' && method !== 'HEAD') {
        init.body = __readBytes(bodyPtr, bodyLen);
    }

    fetch(url, init).then(async (response) => {
        // Lowercase to match HTTP/3 convention the native client uses.
        const headerLines = [];
        response.headers.forEach((value, name) => headerLines.push(`${name.toLowerCase()}: ${value}`));
        const headerStr = headerLines.join('\n');
        const bodyBuf = await response.arrayBuffer();

        const headerEncoded = __encoder.encode(headerStr);
        const headerPtr = headerEncoded.length > 0 ? __allocCopy(headerEncoded) : 0;
        const respBodyPtr = bodyBuf.byteLength > 0 ? __allocCopy(new Uint8Array(bodyBuf)) : 0;
        __wasm().CrafterNetworkOnFetchComplete(callbackId,
            response.status,
            headerPtr, headerEncoded.length,
            respBodyPtr, bodyBuf.byteLength);
    }).catch((err) => {
        const msg = String(err && err.message ? err.message : err);
        const encoded = __encoder.encode(msg);
        const ptr = encoded.length > 0 ? __allocCopy(encoded) : 0;
        __wasm().CrafterNetworkOnFetchError(callbackId, ptr, encoded.length);
    });
}

// ─── WebTransport bridge ──────────────────────────────────────────────
//
// Connection-handle and stream-handle counters are monotone. Each
// connection's incoming-stream + datagram reader loops are started as
// soon as wt.ready resolves and run until the session closes. Outgoing
// operations queued before ready are gated behind a per-handle `ready`
// promise.

let __wtNextHandle = 0;
let __wtNextStream = 0;
const __wtSessions = new Map();   // handle → { wt, ready, streams: Set<streamId> }
const __wtStreams  = new Map();   // streamId → { connection, writer, reader, writable, readable }

function crafterNetworkWtConnect(hostPtr, hostLen, port, alpnPtr, alpnLen, certHashPtr, certHashLen) {
    const host = __readUtf8(hostPtr, hostLen);
    const alpn = __readUtf8(alpnPtr, alpnLen);
    const url  = `https://${host}:${port}/${alpn}`;
    const opts = {};
    if (certHashLen > 0) {
        const hash = __readBytes(certHashPtr, certHashLen);
        opts.serverCertificateHashes = [{ algorithm: 'sha-256', value: hash }];
    }

    let wt;
    try {
        wt = new WebTransport(url, opts);
    } catch (err) {
        console.error('Crafter.Network: WebTransport ctor failed:', err);
        return 0;
    }

    const handle = ++__wtNextHandle;
    const session = { wt, ready: false, streams: new Set(), closed: false };
    __wtSessions.set(handle, session);

    wt.ready.then(() => {
        session.ready = true;
        __wasm().CrafterNetworkOnWtReady(handle);
        __wtRunIncomingLoop(handle, wt.incomingBidirectionalStreams, /*bidi=*/true);
        __wtRunIncomingLoop(handle, wt.incomingUnidirectionalStreams, /*bidi=*/false);
        __wtRunDatagramLoop(handle, wt);
    }).catch((err) => {
        __wtFireClosed(handle, String(err && err.message ? err.message : err));
    });

    wt.closed.then(() => {
        __wtFireClosed(handle, '');
    }).catch((err) => {
        __wtFireClosed(handle, String(err && err.message ? err.message : err));
    });

    return handle;
}

function __wtFireClosed(handle, message) {
    const session = __wtSessions.get(handle);
    if (!session || session.closed) return;
    session.closed = true;
    // Wake up any per-stream receivers with a synthetic FIN so the C++
    // state machine terminates pending callbacks instead of hanging.
    for (const streamId of session.streams) {
        __wasm().CrafterNetworkOnWtStreamChunk(streamId, 0, 0, 1);
        __wtStreams.delete(streamId);
    }
    session.streams.clear();
    const msgPtr = message ? __allocUtf8(message) : 0;
    __wasm().CrafterNetworkOnWtClosed(handle, msgPtr, message ? __encoder.encode(message).length : 0);
}

function crafterNetworkWtClose(handle) {
    const session = __wtSessions.get(handle);
    if (!session) return;
    try { session.wt.close(); } catch (_) { /* already closing */ }
    __wtSessions.delete(handle);
}

function crafterNetworkWtOpenStream(handle, unidirectional) {
    const session = __wtSessions.get(handle);
    if (!session || session.closed) return 0;
    const streamId = ++__wtNextStream;
    const record = { connection: handle, writer: null, reader: null,
                     pendingOps: [], opened: false, unidirectional: !!unidirectional };
    __wtStreams.set(streamId, record);
    session.streams.add(streamId);

    const opener = session.ready
        ? Promise.resolve()
        : session.wt.ready;
    opener.then(() => {
        const p = unidirectional
            ? session.wt.createUnidirectionalStream()
            : session.wt.createBidirectionalStream();
        return p;
    }).then((stream) => {
        // For a bidi stream `stream` is a WebTransportBidirectionalStream
        // with .readable and .writable. For a unidi outgoing stream
        // `stream` is itself a WritableStream.
        if (unidirectional) {
            record.writer = stream.getWriter();
        } else {
            record.writer = stream.writable.getWriter();
            record.reader = stream.readable.getReader();
            __wtRunStreamReader(streamId);
        }
        record.opened = true;
        for (const op of record.pendingOps) op();
        record.pendingOps.length = 0;
    }).catch((err) => {
        console.error(`Crafter.Network: openStream(${streamId}) failed`, err);
        // Tell C++ the stream is dead so pending receivers unblock.
        __wasm().CrafterNetworkOnWtStreamChunk(streamId, 0, 0, 1);
        __wtStreams.delete(streamId);
        session.streams.delete(streamId);
    });

    return streamId;
}

function crafterNetworkWtStreamWrite(streamId, bufPtr, bufLen, finish, callbackId) {
    const record = __wtStreams.get(streamId);
    if (!record) {
        if (callbackId !== 0) __wasm().CrafterNetworkOnWtStreamWriteComplete(callbackId);
        return;
    }
    const data = bufLen > 0 ? __readBytes(bufPtr, bufLen) : new Uint8Array(0);
    const doWrite = () => {
        const p = data.length > 0 ? record.writer.write(data) : Promise.resolve();
        p.then(() => {
            if (finish) { try { return record.writer.close(); } catch (_) {} }
        }).then(() => {
            if (callbackId !== 0) __wasm().CrafterNetworkOnWtStreamWriteComplete(callbackId);
        }).catch((err) => {
            console.error(`Crafter.Network: write(${streamId}) failed`, err);
            if (callbackId !== 0) __wasm().CrafterNetworkOnWtStreamWriteComplete(callbackId);
        });
    };
    if (record.opened) doWrite();
    else record.pendingOps.push(doWrite);
}

function crafterNetworkWtStreamStop(streamId) {
    const record = __wtStreams.get(streamId);
    if (!record) return;
    try { record.writer && record.writer.close(); } catch (_) {}
    try { record.reader && record.reader.cancel(); } catch (_) {}
    const session = __wtSessions.get(record.connection);
    if (session) session.streams.delete(streamId);
    __wtStreams.delete(streamId);
}

function crafterNetworkWtSendDatagram(handle, bufPtr, bufLen) {
    const session = __wtSessions.get(handle);
    if (!session || session.closed) return;
    const data = __readBytes(bufPtr, bufLen);
    const send = () => {
        const writer = session.wt.datagrams.writable.getWriter();
        writer.write(data).catch((err) => {
            console.error('Crafter.Network: sendDatagram failed', err);
        }).finally(() => {
            try { writer.releaseLock(); } catch (_) {}
        });
    };
    if (session.ready) send();
    else session.wt.ready.then(send).catch(() => {});
}

async function __wtRunStreamReader(streamId) {
    const record = __wtStreams.get(streamId);
    if (!record || !record.reader) return;
    try {
        while (true) {
            const { value, done } = await record.reader.read();
            if (value && value.byteLength > 0) {
                const ptr = __allocCopy(value);
                __wasm().CrafterNetworkOnWtStreamChunk(streamId, ptr, value.byteLength, done ? 1 : 0);
            } else if (done) {
                __wasm().CrafterNetworkOnWtStreamChunk(streamId, 0, 0, 1);
            }
            if (done) break;
        }
    } catch (err) {
        // Reader cancelled or stream closed. Dispatch a synthetic FIN so
        // any pending C++ receiver wakes up.
        __wasm().CrafterNetworkOnWtStreamChunk(streamId, 0, 0, 1);
    }
}

async function __wtRunIncomingLoop(handle, source, bidi) {
    const session = __wtSessions.get(handle);
    if (!session) return;
    const reader = source.getReader();
    try {
        while (true) {
            const { value, done } = await reader.read();
            if (done) break;
            const streamId = ++__wtNextStream;
            const record = { connection: handle, writer: null, reader: null,
                             pendingOps: [], opened: true, unidirectional: !bidi };
            if (bidi) {
                record.writer = value.writable.getWriter();
                record.reader = value.readable.getReader();
            } else {
                record.reader = value.getReader();
            }
            __wtStreams.set(streamId, record);
            session.streams.add(streamId);
            __wasm().CrafterNetworkOnWtIncomingStream(handle, streamId, bidi ? 1 : 0);
            __wtRunStreamReader(streamId);
        }
    } catch (_) { /* session closed */ }
}

async function __wtRunDatagramLoop(handle, wt) {
    const reader = wt.datagrams.readable.getReader();
    try {
        while (true) {
            const { value, done } = await reader.read();
            if (done) break;
            if (value && value.byteLength > 0) {
                const ptr = __allocCopy(value);
                __wasm().CrafterNetworkOnWtDatagram(handle, ptr, value.byteLength);
            }
        }
    } catch (_) { /* session closed */ }
}

// ─── Export env object ────────────────────────────────────────────────

if (!window.crafter_webbuild_env) {
    window.crafter_webbuild_env = {};
}
Object.assign(window.crafter_webbuild_env, {
    crafterNetworkFetch,
    crafterNetworkWtConnect,
    crafterNetworkWtClose,
    crafterNetworkWtOpenStream,
    crafterNetworkWtStreamWrite,
    crafterNetworkWtStreamStop,
    crafterNetworkWtSendDatagram,
});