//----------------------------------------------------------------------------//
//                           GNU GPL OS/K                                     //
//                                                                            //
//  Desc:       Command line parsing utilities                                //
//                                                                            //
//                                                                            //
//  Copyright © 2018-2019 The OS/K Team                                       //
//                                                                            //
//  This file is part of OS/K.                                                //
//                                                                            //
//  OS/K is free software: you can redistribute it and/or modify              //
//  it under the terms of the GNU General Public License as published by      //
//  the Free Software Foundation, either version 3 of the License, or         //
//  any later version.                                                        //
//                                                                            //
//  OS/K is distributed in the hope that it will be useful,                   //
//  but WITHOUT ANY WARRANTY//without even the implied warranty of            //
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the             //
//  GNU General Public License for more details.                              //
//                                                                            //
//  You should have received a copy of the GNU General Public License         //
//  along with OS/K.  If not, see <https://www.gnu.org/licenses/>.            //
//----------------------------------------------------------------------------//

#include <ex/argv.h>
#include <ex/malloc.h>

#include <kernel.h>

//
// Computes argument count, the least N such
// that argv[N] == NULL
//
int KalComputeArgCount(const char **argv)
{
    int argc = 0;

    while (argv[argc]) argc++;

    return argc;
}

//
// Computes the total size of argv, including
// the null-terminators
//
size_t KalComputeArgVecSize(const char *argv[])
{
    size_t len;

    for (len = 0; *argv; len += strlen(*argv) + 1, argv++);

    return len;
}

//
// Converts command line to an argument vector
//
// This function assumes that argv[0] is a pointer
// to a ARG_MAX-wide buffer, which will be filled
// with strings in succession; the address of the nth
// string will be stored in argv[n-1]
//
// Technically ARG_MAX is the maximum number of bytes
// in both the buffer *and* argv, i.e. (argc + 1) * sizeof(char *)
// bytes are reserved for the argv[i] pointers, so in fact less than
// ARG_MAX bytes are available
//
// That available space, however, remains strictly higher than 4KB,
// which is the POSIX minimum; the current ARG_MAX guarantees 16KB available
//
// TODO long escape sequences
//      get program command line if cmdLine == NULL
//
error_t KalCmdLineToArgVecEx(const char  *cmdLine,
                             int         *argcPtr,
                             char       **argv,
                             bool         doEscaping)
{
    int argc = 0;
    char quotes = 0;
    bool started = false;
    bool escaping = false;
    size_t written = 0;
    error_t retcode = EOK;

    assert_always(argv && *argv && cmdLine);

    // An ARG_MAX-wide buffer
    char *buffer = *argv;

    // Null-terminate current argv slot
    // and save the start of next string
    // Macro'd to avoid copypasting code
#define NULLTERM_AND_SAVE               \
        *buffer = 0;                    \
        argv[++argc] = ++buffer;        \
        written += sizeof(char *) + 1;  \

    // Is character a blank character?
    // To be replaced by ctype stuff once
    // that's implemented
#define ISBLANK(c) ((c) == ' ' || (c) == '\t' || (c) == '\n')

    // Both " and ' are valid quotes chars
    // XXX aren't there more?
#define ISQUOTE(c) ((c) == '\'' || (c) == '"')


    // Go through the command line
    for (; *cmdLine; cmdLine++) {

        // Make sure we don't go beyond ARG_MAX bytes
        if (written >= ARG_MAX - (1 + sizeof(char *))) {
            // Sanity check
            assert(written == ARG_MAX - (1 + sizeof(char *)));

            // All we have left is one byte for the null-terminator of the current slot
            // and sizeof(char *) bytes for the NULL at the end of argv
            *buffer = 0;

            // Did we write anything in this slot?
            if (started) {
                argc++;
            }

            // We're done, get out of here
            retcode = ENOMEM;
            break;
        }

        // Switch to next argv slot
        if (ISBLANK(*cmdLine) && !quotes && !escaping) {

            // Has slot even started?
            if (started) {
                started = false;
                NULLTERM_AND_SAVE;
            }

            continue;
        }

        // Escaping next character
        if (*cmdLine == '\\' && !escaping && doEscaping) {
            escaping = true;
            continue;
        }

        // Deal with escape sequences
        if (escaping) {
            if      (*cmdLine == 'n') *buffer++ = '\n';
            else if (*cmdLine == 'r') *buffer++ = '\r';
            else if (*cmdLine == 't') *buffer++ = '\t';
            else if (*cmdLine == 'f') *buffer++ = '\f';
            else if (*cmdLine == 'v') *buffer++ = '\v';

            written++;
            started = true;
            escaping = false;
            continue;
        }

        // Deal with quotes
        if (ISQUOTE(*cmdLine) && !escaping) {

            // Quoted text always fills a whole slot
            // Note that this is the only way an empty
            // string can be put in a slot
            if (!quotes && !started) {
                quotes = *cmdLine;
                started = true;
                continue;
            }

            // End a quote block
            if (quotes == *cmdLine && ISBLANK(cmdLine[1])) {
                quotes = 0;
                started = false;
                NULLTERM_AND_SAVE;
                continue;
            }

            // Quotes were either preceeded by unquoted non-blank text
            // or couldn't close quoted text block because succeeded
            // by text; we consider this " to be escaped and fall through
        }

        // Just a regular character, or it is being escaped
        written++;
        started = true;
        escaping = false;
        *buffer++ = *cmdLine;
    }

    // Ensures that argv[argc] == NULL
    argv[++argc] = NULL;

    // Update *argcPtr, but we don't mind if
    // NULL was passed for argcPtr
    if (argcPtr) {
        *argcPtr = argc;
    }

    return retcode;
}

#undef ISQUOTE
#undef ISBLANK
#undef NULLTERM_AND_SAVE

error_t KalCmdLineToArgVec(const char  *cmdLine,
                           int         *argcPtr,
                           char       **argv)
{
    return KalCmdLineToArgVecEx(cmdLine, argcPtr, argv, false);
}