web/frontend/src/api/dmApi.ts

import { API_BASE_URL } from "../core/config";
import { getAuthHeaders } from "../auth/api";
import { ecdhSharedSecret, deriveWrappingKey } from "../utils/crypto/asymmetric";
import { importAesGcmKey, aesGcmEncrypt, aesGcmDecrypt } from "../utils/crypto/symmetric";
import { randomBytes } from "../utils/crypto/kdf";
import { getCurrentKeys } from "../auth/crypto";
import { request } from "../core/websocket";
import type { SendDMRequest, DmEnvelope, User, DMEditRequest, DmEncryptedJSON, BaseDmEnvelope } from "../core/types";
import { b64, ub64 } from "../utils/utils";

export async function decryptDm(envelope: DmEnvelope, senderPublicKeyB64: string): Promise<string> {
    const keys = getCurrentKeys();
    if (!keys) throw new Error("Keys not initialized");

    // Obtain the key
    const shared = ecdhSharedSecret(keys.privateKey, ub64(senderPublicKeyB64));
    const wkRaw = await deriveWrappingKey(shared, ub64(envelope.salt), new Uint8Array([1]));
    const wk = await importAesGcmKey(wkRaw);
    const mk = await aesGcmDecrypt(wk, ub64(envelope.iv2), ub64(envelope.wrappedMk));

    // Decrypt
    const msg = await aesGcmDecrypt(await importAesGcmKey(mk), ub64(envelope.iv), ub64(envelope.ciphertext));
    return new TextDecoder().decode(msg);
}

export async function fetchUsers(token: string): Promise<User[]> {
    const res = await fetch(`${API_BASE_URL}/users`, { headers: getAuthHeaders(token, true) });
    if (!res.ok) return [];
    const data = await res.json();
    return data.users || [];
}

export async function fetchUserPublicKey(userId: number, token: string): Promise<string | null> {
    const res = await fetch(`${API_BASE_URL}/crypto/public-key/of/${userId}`, { headers: getAuthHeaders(token, true) });
    if (!res.ok) return null;
    const data = await res.json();
    return data.publicKey;
}

export async function fetchDMHistory(userId: number, token: string, limit: number = 50): Promise<DmEnvelope[]> {
    const response = await fetch(`${API_BASE_URL}/dm/history/${userId}?limit=${limit}`, { 
        headers: getAuthHeaders(token, true) 
    });
    if (!response.ok) return [];
    const data = await response.json();
    return data.messages || [];
}

export async function sendDMViaWebSocket(recipientId: number, recipientPublicKeyB64: string, plaintext: string, authToken: string, replyToId?: number): Promise<void> {
    const keys = getCurrentKeys();
    if (!keys) throw new Error("Keys not initialized");

    // Encryption key
    const mk = randomBytes(32);
    const wkSalt = randomBytes(16);
    const shared = ecdhSharedSecret(keys.privateKey, ub64(recipientPublicKeyB64));
    const wkRaw = await deriveWrappingKey(shared, wkSalt, new Uint8Array([1]));
    const wk = await importAesGcmKey(wkRaw);

    // Encrypt the message
    const encMsg = await aesGcmEncrypt(await importAesGcmKey(mk), new TextEncoder().encode(plaintext));
    const wrap = await aesGcmEncrypt(wk, mk);

    const payload: SendDMRequest = {
        recipientId: recipientId,
        iv: b64(encMsg.iv),
        ciphertext: b64(encMsg.ciphertext),
        salt: b64(wkSalt),
        iv2: b64(wrap.iv),
        wrappedMk: b64(wrap.ciphertext)
    };
    if (replyToId) payload.replyToId = replyToId;

    await request({
        type: "dmSend",
        credentials: { 
            scheme: "Bearer", 
            credentials: authToken
        },
        data: payload
    });
}

export async function sendDmWithFiles(recipientId: number, recipientPublicKeyB64: string, plaintextJson: string, files: File[], token: string): Promise<void> {
    const keys = getCurrentKeys();
    if (!keys) throw new Error("Keys not initialized");

    const mk = randomBytes(32);
    const wkSalt = randomBytes(16);
    const shared = await ecdhSharedSecret(keys.privateKey, ub64(recipientPublicKeyB64));
    const wkRaw = await deriveWrappingKey(shared, wkSalt, new Uint8Array([1]));
    const wk = await importAesGcmKey(wkRaw);

    const wrap = await aesGcmEncrypt(wk, mk);

    const form = new FormData();
    const names: string[] = [];
    function sliceBuffer(u8: Uint8Array): ArrayBuffer {
        return (u8.buffer as ArrayBuffer).slice(u8.byteOffset, u8.byteOffset + u8.byteLength);
    }

    for (const f of files) {
        // Encrypt file with same mk
        const data = new Uint8Array(await f.arrayBuffer());
        const enc = await aesGcmEncrypt(await importAesGcmKey(mk), data);
        const blob = new Blob([sliceBuffer(enc.iv), sliceBuffer(enc.ciphertext)], { type: "application/octet-stream" });
        const serverName = f.name; // server uses provided name
        names.push(serverName);
        form.append("files", new File([blob], serverName));
    }
    form.append("fileNames", JSON.stringify(names));

    // Merge files metadata into plaintext JSON and encrypt
    let obj: DmEncryptedJSON;
    try {
        obj = JSON.parse(plaintextJson);
    } catch {
        obj = { type: "text", data: { content: String(plaintextJson) } };
    }

    const encMsg = await aesGcmEncrypt(await importAesGcmKey(mk), new TextEncoder().encode(JSON.stringify(obj)));
    form.append("dm_payload", JSON.stringify({
        recipientId: recipientId,
        iv: b64(encMsg.iv),
        ciphertext: b64(encMsg.ciphertext),
        salt: b64(wkSalt),
        iv2: b64(wrap.iv),
        wrappedMk: b64(wrap.ciphertext)
    } satisfies BaseDmEnvelope));

    await fetch(`${API_BASE_URL}/dm/send`, {
        method: "POST",
        headers: getAuthHeaders(token, false),
        body: form
    });
}

export async function editDmEnvelope(id: number, recipientPublicKeyB64: string, newPlaintextJson: string, authToken: string): Promise<void> {
    const keys = getCurrentKeys();
    if (!keys) throw new Error("Keys not initialized");

    // We cannot reuse the old mk safely without knowing it; generate a fresh mk and wrap
    const mk = randomBytes(32);
    const wkSalt = randomBytes(16);
    const shared = await ecdhSharedSecret(keys.privateKey, ub64(recipientPublicKeyB64));
    const wkRaw = await deriveWrappingKey(shared, wkSalt, new Uint8Array([1]));
    const wk = await importAesGcmKey(wkRaw);
    const encMsg = await aesGcmEncrypt(await importAesGcmKey(mk), new TextEncoder().encode(newPlaintextJson));
    const wrap = await aesGcmEncrypt(wk, mk);

    await request({
        type: "dmEdit",
        credentials: { scheme: "Bearer", credentials: authToken },
        data: {
            id,
            iv: b64(encMsg.iv),
            ciphertext: b64(encMsg.ciphertext),
            iv2: b64(wrap.iv),
            wrappedMk: b64(wrap.ciphertext),
            salt: b64(wkSalt)
        }
    } as DMEditRequest);
}

export async function deleteDmEnvelope(id: number, recipientId: number, authToken: string): Promise<void> {
    await request({
        type: "dmDelete",
        credentials: { scheme: "Bearer", credentials: authToken },
        data: { id, recipientId }
    });
}