// TODO: Make types for allt he proto events. This is quite messy without that.

#include "include/chat.h"
#include "include/session.h"

#include <ctype.h>
#include <libwebsockets.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <yyjson.h>

static size_t next_msg_id = 1;

#define CHAT_BUF_SIZE SESSION_CHAT_BUF_SIZE

/*
 * cb_chat - libwebsockets protocol callback.

 * Handles connection lifecycle, incoming messages, and writable events.
 */
int cb_chat(
    struct lws* wsi, enum lws_callback_reasons reason, void* user, void* in,
    size_t len
) {
    Session** ps_p = (Session**)user;
    Session* sess = ps_p ? *ps_p : NULL;
    Session* head = session_get_head();

    switch (reason) {

        case LWS_CALLBACK_ESTABLISHED:
            // New connection, create session.
            if (ps_p) { *ps_p = session_create(wsi); }
            break;

        case LWS_CALLBACK_RECEIVE: {
            // Parse inc JSON packet.
            if (len > CHAT_BUF_SIZE) {
                lwsl_warn(
                    "Received JSON payload exceeds limit: %zu bytes\n", len
                );
                break;
            }
            yyjson_doc* doc = yyjson_read((const char*)in, len, 0);
            if (!doc) break;
            const yyjson_val* root = yyjson_doc_get_root(doc);
            const yyjson_val* tval = yyjson_obj_get((yyjson_val*)root, "type");
            const char* type = (tval && yyjson_is_str((yyjson_val*)tval))
                                   ? yyjson_get_str((yyjson_val*)tval)
                                   : NULL;

            // JOIN.
            if (type && strcmp(type, "join") == 0 && sess) {
                const yyjson_val* data =
                    yyjson_obj_get((yyjson_val*)root, "data");
                const yyjson_val* uval =
                    data ? yyjson_obj_get((yyjson_val*)data, "username") : NULL;
                // Enforce max username length.
                const char* raw_name =
                    (uval && yyjson_is_str((yyjson_val*)uval))
                        ? yyjson_get_str((yyjson_val*)uval)
                        : "Anonymous";
                if (raw_name[0] == '\0') { raw_name = "Anonymous"; }
                char name_buf[SESSION_USERNAME_MAX_LEN];
                size_t _i;
                for (_i = 0; raw_name[_i] && _i < SESSION_USERNAME_MAX_LEN - 1;
                     ++_i) {
                    unsigned char c = (unsigned char)raw_name[_i];
                    name_buf[_i] = isprint(c) ? c : '?';
                }
                name_buf[_i] = '\0';
                session_set_username(sess, name_buf);

                // #1: Welcome our new client.
                {
                    yyjson_mut_doc* wdoc = yyjson_mut_doc_new(NULL);
                    yyjson_mut_val* wroot = yyjson_mut_obj(wdoc);
                    yyjson_mut_doc_set_root(wdoc, wroot);
                    yyjson_mut_obj_add_str(wdoc, wroot, "type", "welcome");

                    yyjson_mut_val* wdata = yyjson_mut_obj(wdoc);
                    yyjson_mut_obj_add_val(wdoc, wroot, "data", wdata);
                    yyjson_mut_obj_add_uint(
                        wdoc, wdata, "you", session_get_id(sess)
                    );

                    yyjson_mut_val* wusers = yyjson_mut_arr(wdoc);
                    yyjson_mut_obj_add_val(wdoc, wdata, "users", wusers);

                    for (Session* s = head; s; s = s->next) {
                        if (session_has_username(s)) {
                            yyjson_mut_val* uobj = yyjson_mut_obj(wdoc);
                            yyjson_mut_arr_add_val(wusers, uobj);
                            yyjson_mut_obj_add_uint(
                                wdoc, uobj, "id", session_get_id(s)
                            );
                            yyjson_mut_obj_add_str(
                                wdoc, uobj, "username", session_get_username(s)
                            );
                        }
                    }

                    size_t out_len;
                    char* out = yyjson_mut_write(wdoc, 0, &out_len);
                    size_t copy_len = out_len < SESSION_CHAT_BUF_SIZE
                                          ? out_len
                                          : SESSION_CHAT_BUF_SIZE;
                    sess->buf_len = copy_len;
                    memcpy(&sess->buf[LWS_PRE], out, copy_len);
                    lws_write(
                        sess->wsi, &sess->buf[LWS_PRE], sess->buf_len,
                        LWS_WRITE_TEXT
                    );

                    free(out);
                    yyjson_mut_doc_free(wdoc);
                }

                // #2: Introduce our new client to everybody else.
                {
                    yyjson_mut_doc* jdoc = yyjson_mut_doc_new(NULL);
                    yyjson_mut_val* jroot = yyjson_mut_obj(jdoc);
                    yyjson_mut_doc_set_root(jdoc, jroot);
                    yyjson_mut_obj_add_str(jdoc, jroot, "type", "join-event");

                    yyjson_mut_val* jdata = yyjson_mut_obj(jdoc);
                    yyjson_mut_obj_add_val(jdoc, jroot, "data", jdata);
                    yyjson_mut_obj_add_uint(
                        jdoc, jdata, "id", session_get_id(sess)
                    );
                    yyjson_mut_obj_add_str(
                        jdoc, jdata, "username", session_get_username(sess)
                    );

                    size_t out_len;
                    char* out = yyjson_mut_write(jdoc, 0, &out_len);
                    size_t copy_len = out_len < SESSION_CHAT_BUF_SIZE
                                          ? out_len
                                          : SESSION_CHAT_BUF_SIZE;
                    for (Session* s = head; s; s = s->next) {
                        s->buf_len = copy_len;
                        memcpy(&s->buf[LWS_PRE], out, copy_len);
                        lws_callback_on_writable(s->wsi);
                    }
                    free(out);
                    yyjson_mut_doc_free(jdoc);
                }
            }
            // NAME.
            else if (type && strcmp(type, "name") == 0 && sess &&
                     session_has_username(sess)) {
                const yyjson_val* dataVal =
                    root ? yyjson_obj_get((yyjson_val*)root, "data") : NULL;
                const yyjson_val* nval =
                    dataVal ? yyjson_obj_get((yyjson_val*)dataVal, "username")
                            : NULL;
                // Enforce max name length.
                const char* raw_newname =
                    (nval && yyjson_is_str((yyjson_val*)nval))
                        ? yyjson_get_str((yyjson_val*)nval)
                        : NULL;
                char newname_buf[SESSION_USERNAME_MAX_LEN];
                if (raw_newname && raw_newname[0] != '\0') {
                    size_t _j;
                    for (_j = 0;
                         raw_newname[_j] && _j < SESSION_USERNAME_MAX_LEN - 1;
                         ++_j) {
                        unsigned char c = (unsigned char)raw_newname[_j];
                        newname_buf[_j] = isprint(c) ? c : '?';
                    }
                    newname_buf[_j] = '\0';
                } else {
                    // Disallow empty names.
                    strcpy(newname_buf, session_get_username(sess));
                }
                const char* newname = newname_buf;
                // Buffer old name before updating.
                char oldname_buf[SESSION_USERNAME_MAX_LEN];
                const char* current = session_get_username(sess);
                if (current) {
                    strncpy(oldname_buf, current, SESSION_USERNAME_MAX_LEN - 1);
                    oldname_buf[SESSION_USERNAME_MAX_LEN - 1] = '\0';
                } else {
                    oldname_buf[0] = '\0';
                }
                // Now update to new name.
                session_set_username(sess, newname);

                // Broadcast name-event to other clients.
                {
                    yyjson_mut_doc* ndoc = yyjson_mut_doc_new(NULL);
                    yyjson_mut_val* nroot = yyjson_mut_obj(ndoc);
                    yyjson_mut_doc_set_root(ndoc, nroot);
                    yyjson_mut_obj_add_str(ndoc, nroot, "type", "name-event");
                    yyjson_mut_val* ndata = yyjson_mut_obj(ndoc);
                    yyjson_mut_obj_add_val(ndoc, nroot, "data", ndata);
                    yyjson_mut_obj_add_uint(
                        ndoc, ndata, "id", session_get_id(sess)
                    );
                    yyjson_mut_obj_add_str(ndoc, ndata, "old", oldname_buf);
                    yyjson_mut_obj_add_str(ndoc, ndata, "new", newname);

                    size_t out_len;
                    char* out = yyjson_mut_write(ndoc, 0, &out_len);
                    size_t copy_len = out_len < SESSION_CHAT_BUF_SIZE
                                          ? out_len
                                          : SESSION_CHAT_BUF_SIZE;
                    for (Session* s = head; s; s = s->next) {
                        s->buf_len = copy_len;
                        memcpy(&s->buf[LWS_PRE], out, copy_len);
                        lws_callback_on_writable(s->wsi);
                    }
                    free(out);
                    yyjson_mut_doc_free(ndoc);
                }
            }
            // MSG.
            else if (type && strcmp(type, "msg") == 0 && sess &&
                     session_has_username(sess)) {
                const yyjson_val* data =
                    yyjson_obj_get((yyjson_val*)root, "data");
                const yyjson_val* cval =
                    data ? yyjson_obj_get((yyjson_val*)data, "content") : NULL;
                // Enforce maximum message content length
                const char* raw_msg = (cval && yyjson_is_str((yyjson_val*)cval))
                                          ? yyjson_get_str((yyjson_val*)cval)
                                          : "";
                char msg_buf[CHAT_BUF_SIZE];
                strncpy(msg_buf, raw_msg, CHAT_BUF_SIZE - 1);
                msg_buf[CHAT_BUF_SIZE - 1] = '\0';
                // Sanitize message to printable characters.
                for (size_t _k = 0; msg_buf[_k]; ++_k) {
                    unsigned char c = (unsigned char)msg_buf[_k];
                    if (!isprint(c)) { msg_buf[_k] = '?'; }
                }
                const char* msg = msg_buf;

                // Build msg-event JSON with ID, parent and timestamp.
                // Get parent ID if present.
                const yyjson_val* dataVal =
                    yyjson_obj_get((yyjson_val*)root, "data");
                const yyjson_val* pval =
                    dataVal ? yyjson_obj_get((yyjson_val*)dataVal, "parent")
                            : NULL;
                uint64_t parent_id = (pval && yyjson_is_uint((yyjson_val*)pval))
                                         ? yyjson_get_uint((yyjson_val*)pval)
                                         : 0;
                time_t now = time(NULL);
                size_t msg_id = next_msg_id++;
                // Send ack with the new message ID.
                {
                    yyjson_mut_doc* ackdoc = yyjson_mut_doc_new(NULL);
                    yyjson_mut_val* ackroot = yyjson_mut_obj(ackdoc);
                    yyjson_mut_doc_set_root(ackdoc, ackroot);
                    yyjson_mut_obj_add_str(ackdoc, ackroot, "type", "msg-ack");
                    yyjson_mut_val* ackdat = yyjson_mut_obj(ackdoc);
                    yyjson_mut_obj_add_val(ackdoc, ackroot, "data", ackdat);
                    yyjson_mut_obj_add_uint(ackdoc, ackdat, "id", msg_id);
                    size_t ack_len;
                    char* ack_out = yyjson_mut_write(ackdoc, 0, &ack_len);
                    size_t copy_ack = ack_len < SESSION_CHAT_BUF_SIZE
                                          ? ack_len
                                          : SESSION_CHAT_BUF_SIZE;
                    sess->buf_len = copy_ack;
                    memcpy(&sess->buf[LWS_PRE], ack_out, copy_ack);
                    lws_write(
                        sess->wsi, &sess->buf[LWS_PRE], sess->buf_len,
                        LWS_WRITE_TEXT
                    );
                    free(ack_out);
                    yyjson_mut_doc_free(ackdoc);
                }

                yyjson_mut_doc* mdoc = yyjson_mut_doc_new(NULL);
                yyjson_mut_val* mroot = yyjson_mut_obj(mdoc);
                yyjson_mut_doc_set_root(mdoc, mroot);
                yyjson_mut_obj_add_str(mdoc, mroot, "type", "msg-event");

                yyjson_mut_val* mdat = yyjson_mut_obj(mdoc);
                yyjson_mut_obj_add_val(mdoc, mroot, "data", mdat);
                yyjson_mut_obj_add_uint(mdoc, mdat, "id", msg_id);
                if (parent_id)
                    yyjson_mut_obj_add_uint(mdoc, mdat, "parent", parent_id);
                else yyjson_mut_obj_add_null(mdoc, mdat, "parent");
                yyjson_mut_obj_add_uint(mdoc, mdat, "ts", (uint64_t)now);
                yyjson_mut_obj_add_str(
                    mdoc, mdat, "username", session_get_username(sess)
                );
                yyjson_mut_obj_add_str(mdoc, mdat, "content", msg);

                size_t out_len;
                char* out = yyjson_mut_write(mdoc, 0, &out_len);
                size_t copy_len = out_len < SESSION_CHAT_BUF_SIZE
                                      ? out_len
                                      : SESSION_CHAT_BUF_SIZE;
                for (Session* s = head; s; s = s->next) {
                    s->buf_len = copy_len;
                    memcpy(&s->buf[LWS_PRE], out, copy_len);
                    lws_callback_on_writable(s->wsi);
                }
                free(out);
                yyjson_mut_doc_free(mdoc);
                // Writable events already scheduled for each session above.
            }

            yyjson_doc_free(doc);
            break;
        }

        case LWS_CALLBACK_SERVER_WRITEABLE:
            if (sess && sess->buf_len > 0) {
                lws_write(
                    sess->wsi, &sess->buf[LWS_PRE], sess->buf_len,
                    LWS_WRITE_TEXT
                );
                sess->buf_len = 0;
            }
            break;

        case LWS_CALLBACK_CLOSED:
            // Goodbye.
            // TODO: Add leave event to proto.
            if (sess) { session_destroy(sess); }
            break;

        default: break;
    }

    return 0;
}