/**
 * Compiler implementation of the D programming language
 * http://dlang.org
 * This file is not shared with other compilers which use the DMD front-end.
 *
 * Copyright:   Copyright (c) 1999-2017 by Digital Mars, All Rights Reserved
 *              Some portions copyright (c) 1994-1995 by Symantec
 * Authors:     $(LINK2 http://www.digitalmars.com, Walter Bright)
 * License:     $(LINK2 http://www.boost.org/LICENSE_1_0.txt, Boost License 1.0)
 * Source:      $(LINK2 https://github.com/dlang/dmd/blob/master/src/ddmd/root/response.d, root/_response.d)
 */

module ddmd.root.response;

// Online documentation: https://dlang.org/phobos/ddmd_root_response.html

import core.stdc.stdio;
import core.stdc.stdlib;
import core.stdc.string;
import ddmd.root.file;
import ddmd.root.filename;

/*********************************
 * #include <stdlib.h>
 * int response_expand(int *pargc,char ***pargv);
 *
 * Expand any response files in command line.
 * Response files are arguments that look like:
 *   @NAME
 * The name is first searched for in the environment. If it is not
 * there, it is searched for as a file name.
 * Arguments are separated by spaces, tabs, or newlines. These can be
 * imbedded within arguments by enclosing the argument in '' or "".
 * Recursively expands nested response files.
 *
 * To use, put the line:
 *   response_expand(&argc,&argv);
 * as the first executable statement in main(int argc, char **argv).
 * argc and argv are adjusted to be the new command line arguments
 * after response file expansion.
 *
 * Digital Mars's MAKE program can be notified that a program can accept
 * long command lines via environment variables by preceding the rule
 * line for the program with a *.
 *
 * Returns:
 *   0   success
 *   !=0   failure (argc, argv unchanged)
 */
bool response_expand(Strings* args)
{
    const(char)* cp;
    int recurse = 0;
    for (size_t i = 0; i < args.dim;)
    {
        cp = (*args)[i];
        if (*cp != '@')
        {
            ++i;
            continue;
        }
        args.remove(i);
        char* buffer;
        char* bufend;
        cp++;
        if (auto p = getenv(cp))
        {
            buffer = strdup(p);
            if (!buffer)
                goto noexpand;
            bufend = buffer + strlen(buffer);
        }
        else
        {
            auto f = File(cp);
            if (f.read())
                goto noexpand;
            f._ref = 1;
            buffer = cast(char*)f.buffer;
            bufend = buffer + f.len;
        }
        // The logic of this should match that in setargv()
        int comment = 0;
        for (auto p = buffer; p < bufend; p++)
        {
            char* d;
            char c, lastc;
            ubyte instring;
            int num_slashes, non_slashes;
            switch (*p)
            {
            case 26:
                /* ^Z marks end of file      */
                goto L2;
            case 0xD:
            case '\n':
                if (comment)
                {
                    comment = 0;
                }
                goto case;
            case 0:
            case ' ':
            case '\t':
                continue;
                // scan to start of argument
            case '#':
                comment = 1;
                continue;
            case '@':
                if (comment)
                {
                    continue;
                }
                recurse = 1;
                goto default;
            default:
                /* start of new argument   */
                if (comment)
                {
                    continue;
                }
                args.insert(i, p);
                ++i;
                instring = 0;
                c = 0;
                num_slashes = 0;
                for (d = p; 1; p++)
                {
                    lastc = c;
                    if (p >= bufend)
                    {
                        *d = 0;
                        goto L2;
                    }
                    c = *p;
                    switch (c)
                    {
                    case '"':
                        /*
                         Yes this looks strange,but this is so that we are
                         MS Compatible, tests have shown that:
                         \\\\"foo bar"  gets passed as \\foo bar
                         \\\\foo  gets passed as \\\\foo
                         \\\"foo gets passed as \"foo
                         and \"foo gets passed as "foo in VC!
                         */
                        non_slashes = num_slashes % 2;
                        num_slashes = num_slashes / 2;
                        for (; num_slashes > 0; num_slashes--)
                        {
                            d--;
                            *d = '\0';
                        }
                        if (non_slashes)
                        {
                            *(d - 1) = c;
                        }
                        else
                        {
                            instring ^= 1;
                        }
                        break;
                    case 26:
                        *d = 0; // terminate argument
                        goto L2;
                    case 0xD:
                        // CR
                        c = lastc;
                        continue;
                        // ignore
                    case '@':
                        recurse = 1;
                        goto Ladd;
                    case ' ':
                    case '\t':
                        if (!instring)
                        {
                        case '\n':
                        case 0:
                            *d = 0; // terminate argument
                            goto Lnextarg;
                        }
                        goto default;
                    default:
                    Ladd:
                        if (c == '\\')
                            num_slashes++;
                        else
                            num_slashes = 0;
                        *d++ = c;
                        break;
                    }
                }
                break;
            }
        Lnextarg:
        }
    L2:
    }
    if (recurse)
    {
        /* Recursively expand @filename   */
        if (response_expand(args))
            goto noexpand;
    }
    return false; /* success         */
noexpand:
    /* error         */
    /* BUG: any file buffers are not free'd   */
    return true;
}
