/* Borland 32-bit shift and Turbo Pascal ShortString helpers from Code5. */

#include "tdkpin_shortstrings.h"

uint32_t borland_shift_right_u32(uint32_t value, uint16_t count)
{
    return value >> (count & 0x1f);
}

uint32_t borland_shift_left_u32(uint32_t value, uint16_t count)
{
    return value << (count & 0x1f);
}

void borland_short_assign(Win16FarPtr destination, Win16FarPtr source)
{
    uint8_t length = win16_read_u8(source);
    win16_write_u8(destination, length);
    for (uint16_t index = 1; index <= length; index++) {
        win16_write_u8(
            win16_far_add_offset(destination, index),
            win16_read_u8(win16_far_add_offset(source, index)));
    }
}

void borland_short_assign_truncated(
    Win16FarPtr destination, Win16FarPtr source, uint8_t maximum_length)
{
    uint8_t length = win16_read_u8(source);
    if (length > maximum_length) {
        length = maximum_length;
    }
    win16_write_u8(destination, length);
    for (uint16_t index = 1; index <= length; index++) {
        win16_write_u8(
            win16_far_add_offset(destination, index),
            win16_read_u8(win16_far_add_offset(source, index)));
    }
}

void borland_short_substring(
    Win16FarPtr destination,
    Win16FarPtr source,
    int16_t index,
    int16_t count)
{
    if (index < 1) {
        index = 1;
    }
    uint16_t source_length = win16_read_u8(source);
    uint16_t available = 0;
    if ((uint16_t)index <= source_length) {
        available = (uint16_t)(source_length - (uint16_t)index + 1);
    }
    uint16_t requested = count < 0 ? 0 : (uint16_t)count;
    uint8_t copied = (uint8_t)(available < requested ? available : requested);
    win16_write_u8(destination, copied);
    for (uint16_t offset = 0; offset < copied; offset++) {
        win16_write_u8(
            win16_far_add_offset(destination, (uint16_t)(offset + 1)),
            win16_read_u8(win16_far_add_offset(
                source, (uint16_t)((uint16_t)index + offset))));
    }
}

void borland_short_concat(Win16FarPtr destination, Win16FarPtr source)
{
    uint8_t destination_length = win16_read_u8(destination);
    uint8_t source_length = win16_read_u8(source);
    uint16_t sum = (uint16_t)destination_length + source_length;
    uint8_t copied = source_length;
    if (sum > 0xff) {
        copied = (uint8_t)~destination_length;
        win16_write_u8(destination, 0xff);
    } else {
        win16_write_u8(destination, (uint8_t)sum);
    }
    for (uint16_t index = 1; index <= copied; index++) {
        win16_write_u8(
            win16_far_add_offset(
                destination, (uint16_t)(destination_length + index)),
            win16_read_u8(win16_far_add_offset(source, index)));
    }
}

uint16_t borland_short_position(Win16FarPtr pattern, Win16FarPtr text)
{
    uint8_t pattern_length = win16_read_u8(pattern);
    uint8_t text_length = win16_read_u8(text);
    if (pattern_length == 0 || pattern_length > text_length) {
        return 0;
    }
    uint16_t last = (uint16_t)(text_length - pattern_length + 1);
    for (uint16_t position = 1; position <= last; position++) {
        bool equal = true;
        for (uint16_t index = 1; index <= pattern_length; index++) {
            if (win16_read_u8(win16_far_add_offset(pattern, index)) !=
                win16_read_u8(win16_far_add_offset(
                    text, (uint16_t)(position + index - 1)))) {
                equal = false;
                break;
            }
        }
        if (equal) {
            return position;
        }
    }
    return 0;
}

/* Materialize the original FLAGS-only comparison as a signed C result. */
int16_t borland_short_compare(Win16FarPtr left, Win16FarPtr right)
{
    uint8_t left_length = win16_read_u8(left);
    uint8_t right_length = win16_read_u8(right);
    uint8_t common = left_length < right_length ? left_length : right_length;
    for (uint16_t index = 1; index <= common; index++) {
        uint8_t left_byte = win16_read_u8(win16_far_add_offset(left, index));
        uint8_t right_byte = win16_read_u8(win16_far_add_offset(right, index));
        if (left_byte != right_byte) {
            return (int16_t)left_byte - right_byte;
        }
    }
    return (int16_t)left_length - right_length;
}

void borland_character_to_short(Win16FarPtr destination, uint8_t character)
{
    win16_write_u8(destination, 1);
    win16_write_u8(win16_far_add_offset(destination, 1), character);
}

void borland_bytes_to_short(
    Win16FarPtr destination, Win16FarPtr source, uint16_t count)
{
    win16_write_u8(destination, (uint8_t)count);
    for (uint16_t index = 0; index < count; index++) {
        win16_write_u8(
            win16_far_add_offset(destination, (uint16_t)(index + 1)),
            win16_read_u8(win16_far_add_offset(source, index)));
    }
}

static uint8_t copy_short_slice(
    uint8_t *output,
    uint8_t output_length,
    Win16FarPtr source,
    uint16_t first,
    uint16_t count,
    uint8_t maximum)
{
    uint8_t source_length = win16_read_u8(source);
    if (first < 1) {
        first = 1;
    }
    uint16_t available = first <= source_length
        ? (uint16_t)(source_length - first + 1)
        : 0;
    uint16_t copied = available < count ? available : count;
    if (copied > (uint16_t)(maximum - output_length)) {
        copied = (uint16_t)(maximum - output_length);
    }
    for (uint16_t offset = 0; offset < copied; offset++) {
        output[output_length++] = win16_read_u8(win16_far_add_offset(
            source, (uint16_t)(first + offset)));
    }
    return output_length;
}

/* 1020:0b1b — Insert(insertion,destination,index) with destination max length. */
void borland_short_insert(
    Win16FarPtr destination,
    Win16FarPtr insertion,
    int16_t index,
    uint8_t maximum_length)
{
    if (index < 1) {
        index = 1;
    }
    uint8_t result[255];
    uint8_t length = 0;
    length = copy_short_slice(
        result, length, destination, 1, (uint16_t)(index - 1), maximum_length);
    length = copy_short_slice(
        result, length, insertion, 1, 255, maximum_length);
    length = copy_short_slice(
        result, length, destination, (uint16_t)index, 255, maximum_length);

    win16_write_u8(destination, length);
    for (uint16_t offset = 0; offset < length; offset++) {
        win16_write_u8(
            win16_far_add_offset(destination, (uint16_t)(offset + 1)),
            result[offset]);
    }
}

/* 1020:0b7a — Delete(string,index,count); invalid ranges leave it unchanged. */
void borland_short_delete(Win16FarPtr string, int16_t index, int16_t count)
{
    if (index <= 0 || count <= 0 || count >= 256) {
        return;
    }
    if (index > 255) {
        index = 255;
    }
    uint8_t result[255];
    uint8_t length = 0;
    length = copy_short_slice(
        result, length, string, 1, (uint16_t)(index - 1), 255);
    length = copy_short_slice(
        result, length, string, (uint16_t)(index + count), 255, 255);

    win16_write_u8(string, length);
    for (uint16_t offset = 0; offset < length; offset++) {
        win16_write_u8(
            win16_far_add_offset(string, (uint16_t)(offset + 1)), result[offset]);
    }
}