// formsrv.c - Remote forms server library implementation

#define _POSIX_C_SOURCE 200809L

#include "formsrv.h"

#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

// ---------------------------------------------------------------------------
// Constants
// ---------------------------------------------------------------------------

#define MAX_MSG_LEN    4096

// ---------------------------------------------------------------------------
// Types
// ---------------------------------------------------------------------------

struct FormServerS {
    FormTransportT *transport;
    EventCallbackT  eventCallback;
    void           *eventUserData;
    int32_t         nextFormId;
    char            msgBuf[MAX_MSG_LEN];
};

// ---------------------------------------------------------------------------
// Prototypes
// ---------------------------------------------------------------------------

static bool parseToken(const char **p, char *buf, int32_t bufSize);
static void rewriteFormId(char *line, int32_t lineSize, int32_t formId);
static void sendCommand(FormServerT *server, const char *fmt, ...);
static bool skipSpaces(const char **p);


// ---------------------------------------------------------------------------
// Internal helpers
// ---------------------------------------------------------------------------

static bool parseToken(const char **p, char *buf, int32_t bufSize) {
    skipSpaces(p);
    if (**p == '\0') {
        return false;
    }

    int32_t i = 0;

    if (**p == '"') {
        // Quoted string — read until closing quote
        (*p)++;
        while (**p != '\0' && **p != '"') {
            if (**p == '\\' && *(*p + 1) != '\0') {
                (*p)++;
                char c = **p;
                switch (c) {
                    case 'n':  c = '\n'; break;
                    case 'r':  c = '\r'; break;
                    case 't':  c = '\t'; break;
                    case '"':  c = '"';  break;
                    case '\\': c = '\\'; break;
                    default:   break;
                }
                if (i < bufSize - 1) {
                    buf[i++] = c;
                }
            } else {
                if (i < bufSize - 1) {
                    buf[i++] = **p;
                }
            }
            (*p)++;
        }
        if (**p == '"') {
            (*p)++;
        }
    } else {
        // Bare token — read until whitespace
        while (**p != '\0' && **p != ' ' && **p != '\t') {
            if (i < bufSize - 1) {
                buf[i++] = **p;
            }
            (*p)++;
        }
    }

    buf[i] = '\0';
    return i > 0;
}


static void rewriteFormId(char *line, int32_t lineSize, int32_t formId) {
    // Protocol lines have the form: COMMAND <formId> <rest...>
    // Skip command prefix (non-space chars)
    char *p = line;
    while (*p && *p != ' ') {
        p++;
    }
    // Skip spaces
    while (*p == ' ') {
        p++;
    }

    // p now points at the placeholder ID token ("0")
    // Find the end of this token
    char *idStart = p;
    while (*p && *p != ' ' && *p != '\t' && *p != '\n' && *p != '\r') {
        p++;
    }
    char *idEnd = p;

    // Format the new ID
    char idBuf[16];
    int32_t idLen = snprintf(idBuf, sizeof(idBuf), "%d", formId);

    int32_t oldLen = (int32_t)(idEnd - idStart);
    int32_t shift  = idLen - oldLen;

    // Check that the rewritten line still fits
    int32_t curLen = (int32_t)strlen(line);
    if (curLen + shift >= lineSize - 1) {
        return;
    }

    // Shift the remainder of the line
    if (shift != 0) {
        memmove(idStart + idLen, idEnd, strlen(idEnd) + 1);
    }

    // Write the new ID (no NUL — the memmove already placed the rest)
    memcpy(idStart, idBuf, idLen);
}


static void sendCommand(FormServerT *server, const char *fmt, ...) {
    char    buf[MAX_MSG_LEN];
    va_list args;

    va_start(args, fmt);
    vsnprintf(buf, sizeof(buf), fmt, args);
    va_end(args);

    server->transport->writeMessage(buf, server->transport->ctx);
}


static bool skipSpaces(const char **p) {
    while (**p == ' ' || **p == '\t') {
        (*p)++;
    }
    return **p != '\0';
}


// ---------------------------------------------------------------------------
// Public API
// ---------------------------------------------------------------------------

void formServerBindEvent(FormServerT *server, int32_t formId, int32_t ctrlId, const char *eventName) {
    sendCommand(server, "EVENT.BIND %d %d %s", formId, ctrlId, eventName);
}


FormServerT *formServerCreate(FormTransportT *transport) {
    FormServerT *server = (FormServerT *)calloc(1, sizeof(FormServerT));
    if (server == NULL) {
        return NULL;
    }
    server->transport  = transport;
    server->nextFormId = 1;
    return server;
}


void formServerDestroy(FormServerT *server) {
    if (server == NULL) {
        return;
    }
    free(server);
}


void formServerDestroyForm(FormServerT *server, int32_t formId) {
    sendCommand(server, "FORM.DESTROY %d", formId);
}


void formServerHideForm(FormServerT *server, int32_t formId) {
    sendCommand(server, "FORM.HIDE %d", formId);
}


bool formServerPollEvent(FormServerT *server) {
    int bytesRead = server->transport->readMessage(
        server->msgBuf, MAX_MSG_LEN - 1, server->transport->ctx);

    if (bytesRead <= 0) {
        return false;
    }

    server->msgBuf[bytesRead] = '\0';

    // Parse: EVENT <formId> <ctrlId> <eventName> [<data>]
    const char *p = server->msgBuf;
    char        token[256];

    if (!parseToken(&p, token, sizeof(token))) {
        return false;
    }
    if (strcmp(token, "EVENT") != 0) {
        return false;
    }

    // formId
    if (!parseToken(&p, token, sizeof(token))) {
        return false;
    }
    int32_t formId = (int32_t)atoi(token);

    // ctrlId
    if (!parseToken(&p, token, sizeof(token))) {
        return false;
    }
    int32_t ctrlId = (int32_t)atoi(token);

    // eventName
    char eventName[64];
    if (!parseToken(&p, eventName, sizeof(eventName))) {
        return false;
    }

    // Remaining data (rest of line after skipping spaces)
    skipSpaces(&p);
    const char *data = p;

    if (server->eventCallback != NULL) {
        server->eventCallback(formId, ctrlId, eventName, data,
                              server->eventUserData);
    }

    return true;
}


int32_t formServerSendForm(FormServerT *server, const char *path) {
    FILE *f = fopen(path, "r");
    if (f == NULL) {
        fprintf(stderr, "formsrv: cannot open '%s': %s\n", path, strerror(errno));
        return -1;
    }

    int32_t formId = server->nextFormId++;
    char    lineBuf[MAX_MSG_LEN];

    while (fgets(lineBuf, sizeof(lineBuf), f) != NULL) {
        // Strip trailing newline
        int32_t len = (int32_t)strlen(lineBuf);
        while (len > 0 && (lineBuf[len - 1] == '\n' || lineBuf[len - 1] == '\r')) {
            lineBuf[--len] = '\0';
        }

        // Skip empty lines
        if (len == 0) {
            continue;
        }

        rewriteFormId(lineBuf, sizeof(lineBuf), formId);
        server->transport->writeMessage(lineBuf, server->transport->ctx);
    }

    fclose(f);
    return formId;
}


void formServerSetEventCallback(FormServerT *server, EventCallbackT cb, void *userData) {
    server->eventCallback = cb;
    server->eventUserData = userData;
}


void formServerSetProp(FormServerT *server, int32_t formId, int32_t ctrlId, const char *prop, const char *value) {
    sendCommand(server, "CTRL.SET %d %d %s=%s", formId, ctrlId, prop, value);
}


void formServerShowForm(FormServerT *server, int32_t formId) {
    sendCommand(server, "FORM.SHOW %d", formId);
}


void formServerUnbindEvent(FormServerT *server, int32_t formId, int32_t ctrlId, const char *eventName) {
    sendCommand(server, "EVENT.UNBIND %d %d %s", formId, ctrlId, eventName);
}