#include "decoderthread.h"

DecoderThread::DecoderThread(QObject *parent) :
    QThread(parent)
{
}

DecoderThread::~DecoderThread()
{
    wait();
}

void DecoderThread::decode(QByteArray program, QByteArray input)
{
    this->program = program;
    this->input = input;
    start();
}

void DecoderThread::run()
{
    char* program = new char[this->program.size() + 1];
    strcpy(program, this->program.data());
    int programLength = this->program.size();

    char* input = new char[this->input.size() + 1];
    strcpy(input, this->input.data());
    int inputLength = this->program.size();

    actualDecode(program, programLength, input, inputLength);

    delete program;
    delete input;
}

void DecoderThread::actualDecode(char* program, int programLength, char* input, int inputLength)
{
    // Don't use QList or QByteArray, it's too slow
    char memory[65536];
    int ptr = 0;

    QString text;
    QMap<int,int> correspondingBraces;
    QStack<int> loopStack;

    int programIndex = 0;
    int inputIndex = 0;

    for (programIndex = 0; programIndex < programLength; ++programIndex) {
        switch (program[programIndex]) {
        case '[':
            loopStack.push(programIndex);
        break;
        case ']':
            if(loopStack.isEmpty()) {
                emit errorMessage("Unmatched end of loop");
                return;
            }
            int old_i = loopStack.pop();
            correspondingBraces.insert(programIndex, old_i);
            correspondingBraces.insert(old_i, programIndex);
        break;
        }
    }
    if(!loopStack.isEmpty()) {
        emit errorMessage("Unmatched begin of loop");
        return;
    }

    for (programIndex = 0; programIndex < programLength; ++programIndex) {
        switch (program[programIndex]) {
        case '>':
            ++ptr;
            break;
        case '<':
            --ptr;
            break;
        case '+':
            ++memory[ptr];
            break;
        case '-':
            --memory[ptr];
            break;
        case '.':
            text += (QString(memory[ptr]));
            if (memory[ptr] == '\n') {
                emit programDecoded(text);
            }
            break;
        case ',':
            if (inputIndex < inputLength) {
                memory[ptr] = input[inputIndex];
                ++inputIndex;
            } else {
                memory[ptr] = 0;
            }
            break;
        case '[':
            if (memory[ptr] == 0) {
                programIndex = correspondingBraces.value(programIndex);
            }
            break;
        case ']':
            if (memory[ptr] != 0) {
                programIndex = correspondingBraces.value(programIndex);
            }
            break;
        }
    }

    emit programDecoded(text);
}