/* DOS/Win16 path and environment helpers used by CTL3D discovery. */

#include "tdkpin_multimedia.h"

#include "tdkpin_strings.h"

/*
 * 1008:2608 -- copy at most 79 ANSI bytes to a stack ASCIIZ buffer, translate
 * it in-place to OEM, then issue DOS AX=4300h.  The helper's original register
 * interface preserves CX for the returned attributes; the typed bridge makes
 * carry and that CX value explicit.
 */
Win16DosFileAttributesResult borland_dos_get_file_attributes_ansi(
    Win16FarPtr name)
{
    uint8_t oem_name[80];
    uint16_t copied = 0;
    while (copied < 79) {
        uint8_t byte = win16_read_u8(win16_far_add_offset(name, copied));
        if (byte == 0) {
            break;
        }
        oem_name[copied++] = byte;
    }
    oem_name[copied] = 0;
    Win16FarPtr local = win16_stack_pointer(oem_name);
    (void)AnsiToOem16(local, local);
    return win16_dos_get_file_attributes(local);
}

static uint16_t append_c_string(
    Win16FarPtr output,
    uint16_t cursor,
    uint16_t *remaining,
    Win16FarPtr source)
{
    uint16_t source_index = 0;
    while (*remaining != 0) {
        uint8_t byte = win16_read_u8(
            win16_far_add_offset(source, source_index++));
        if (byte == 0) {
            break;
        }
        win16_write_u8(win16_far_add_offset(output, cursor++), byte);
        (*remaining)--;
    }
    win16_write_u8(win16_far_add_offset(output, cursor), 0);
    return cursor;
}

/*
 * 1008:2643 -- search for file_name first as given, then under each semicolon-
 * separated directory.  Result capacity is exactly 79 characters plus NUL.
 * DOS volume labels/directories (attribute bits 08/10) do not count as files.
 */
Win16FarPtr multimedia_search_file(
    Win16FarPtr search_path,
    Win16FarPtr file_name,
    Win16FarPtr result)
{
    uint16_t search_index = 0;
    uint16_t remaining = 79;
    uint16_t cursor = append_c_string(result, 0, &remaining, file_name);

    for (;;) {
        Win16DosFileAttributesResult attributes =
            borland_dos_get_file_attributes_ansi(result);
        if (!attributes.carry && (attributes.attributes & 0x18u) == 0) {
            return result;
        }

        remaining = 79;
        cursor = 0;
        uint8_t character = win16_read_u8(
            win16_far_add_offset(search_path, search_index));
        uint8_t last_copied = 0;
        if (character == 0) {
            win16_write_u8(result, 0);
            return result;
        }

        for (;;) {
            search_index++;
            if (character == ';') {
                break;
            }
            if (remaining != 0) {
                last_copied = character;
                win16_write_u8(
                    win16_far_add_offset(result, cursor++), character);
                remaining--;
            }
            character = win16_read_u8(
                win16_far_add_offset(search_path, search_index));
            if (character == 0) {
                break;
            }
        }

        if (remaining != 0 && last_copied != ':' && last_copied != '\\') {
            win16_write_u8(win16_far_add_offset(result, cursor++), '\\');
            remaining--;
        }
        cursor = append_c_string(
            result, cursor, &remaining, file_name);
    }
}

/*
 * 1008:26b0 -- Borland-style path splitter.  Optional outputs receive the
 * directory/drive prefix (max 67), basename (max 8), and extension (max 4).
 * Return bits are 8 wildcard, 4 prefix, 2 basename, and 1 extension.
 */
uint16_t multimedia_split_path(
    Win16FarPtr extension,
    Win16FarPtr file_name,
    Win16FarPtr directory,
    Win16FarPtr input)
{
    Win16FarPtr base = borland_far_strrchr(input, '\\');
    if (base == 0) {
        base = borland_far_strrchr(input, ':');
    }
    if (base == 0) {
        base = input;
    } else {
        base = win16_far_add_offset(base, 1);
    }

    Win16FarPtr dot = borland_far_strchr(base, '.');
    if (dot == 0) {
        dot = borland_far_strend(base);
    }

    uint16_t prefix_length = (uint16_t)(
        win16_far_offset(base) - win16_far_offset(input));
    if (prefix_length > 0x43) {
        prefix_length = 0x43;
    }
    uint16_t name_length = (uint16_t)(
        win16_far_offset(dot) - win16_far_offset(base));
    if (name_length > 8) {
        name_length = 8;
    }

    uint16_t flags = 0;
    if (borland_far_strchr(base, '?') != 0 ||
        borland_far_strchr(base, '*') != 0) {
        flags |= 8;
    }
    if (prefix_length != 0) {
        flags |= 4;
    }
    if (name_length != 0) {
        flags |= 2;
    }
    if (win16_read_u8(dot) != 0) {
        flags |= 1;
    }

    if (directory != 0) {
        (void)borland_far_strncpy(directory, input, prefix_length);
    }
    if (file_name != 0) {
        (void)borland_far_strncpy(file_name, base, name_length);
    }
    if (extension != 0) {
        (void)borland_far_strncpy(extension, dot, 4);
    }
    return flags;
}

/* 1008:2819 -- case-insensitive NAME= lookup in the DOS environment block. */
Win16FarPtr multimedia_environment_value(Win16FarPtr name)
{
    uint16_t name_length = borland_far_strlen(name);
    Win16FarPtr variable = GetDOSEnvironment16();
    while (win16_read_u8(variable) != 0) {
        if (borland_far_strnicmp(name, variable, name_length) == 0 &&
            win16_read_u8(win16_far_add_offset(variable, name_length)) == '=') {
            return win16_far_add_offset(variable, (uint16_t)(name_length + 1));
        }
        variable = win16_far_add_offset(
            variable, (uint16_t)(borland_far_strlen(variable) + 1));
    }
    return 0;
}