char* parser_file;
int parser_line;
int parser_col;

#define inject_scl(_ret)                                         \
    ret->sourceCodeLocation = new(Source_Code_Location);         \
    ret->sourceCodeLocation->file   = parser_file;               \
    ret->sourceCodeLocation->line   = parser_line;               \
    ret->sourceCodeLocation->column = parser_col


// TODO(Felix): use the array list macro here?
Ast_Node_Array_List* create_Ast_Node_Array_List(int initial_length) {
    Ast_Node_Array_List* ret = new (Ast_Node_Array_List);

    // create one with 16 entries first
    ret->length =  initial_length;
    ret->data = (struct Ast_Node**)malloc(initial_length * sizeof(struct Ast_Node));
    ret->next_index = 0;

    return ret;
}

void append_to_Ast_Node_Array_List(Ast_Node_Array_List* list, struct Ast_Node* node) {
    if (list->next_index == list->length) {
        list->length *= 2;
        list->data = (struct Ast_Node**)realloc(list->data, list->length * sizeof(struct Ast_Node));
    }
    list->data[list->next_index++] = node;
}


void eat_comment_line(char* text, int* index_in_text) {
    // safety check if we are actually starting a comment here
    if (text[*index_in_text] != ';')
        return;

    // eat the comment line
    do {
        ++(*index_in_text);
        ++parser_col;
    } while (text[(*index_in_text)] != '\n' &&
             text[(*index_in_text)] != '\r' &&
             text[(*index_in_text)] != '\0');
}

void eat_whitespace(char* text, int* index_in_text) {
    // skip whitespaces
    while (text[(*index_in_text)] == ' '  ||
           text[(*index_in_text)] == '\t' ||
           text[(*index_in_text)] == '\n' ||
           text[(*index_in_text)] == '\r')
    {
        if (text[(*index_in_text)] == '\n') {
            ++parser_line;
            parser_col = 0;
        }
        ++parser_col;
        ++(*index_in_text);
    }

}

void eat_until_code(char* text, int* index_in_text) {
    int position_before;
    do {
        position_before = *index_in_text;
        eat_comment_line(text, index_in_text);
        eat_whitespace(text, index_in_text);
    } while (position_before != *index_in_text);
}

char* read_atom(char* text, int* index_in_text) {
    int atom_length = 0;
    while (text[*index_in_text+atom_length] != ' '  &&
           text[*index_in_text+atom_length] != ')'  &&
           text[*index_in_text+atom_length] != '('  &&
           text[*index_in_text+atom_length] != '\0' &&
           text[*index_in_text+atom_length] != '\n' &&
           text[*index_in_text+atom_length] != '\r' &&
           text[*index_in_text+atom_length] != '\t')
    {
        ++atom_length;
    }

    // let's mark the end of the atom there quickly, so the string can
    // be copied from there easily and then put the char that was
    // before there back
    char before = text[*index_in_text+atom_length];
    text[*index_in_text+atom_length] = '\0';

    // get the atom
    char* atom = (char*)malloc(atom_length*sizeof(char)+1); // plus null char
    strcpy(atom, text+(*index_in_text));

    // restore the original string
    text[*index_in_text+atom_length] = before;

    // update the index to point to the character after the atom
    // ended
    *index_in_text += atom_length;

    return atom;
}

Ast_Node* parse_number(char* text, int* index_in_text) {
    double number;
    char* str_number = read_atom(text, index_in_text);
    sscanf(str_number, "%lf", &number);
    Ast_Node* ret = create_ast_node_number(number);
    inject_scl(ret);
    return ret;
}


Ast_Node* parse_keyword(char* text, int* index_in_text) {
    // we are now on the colon
    ++(*index_in_text);
    ++parser_col;
    char* str_keyword = read_atom(text, index_in_text);
    Ast_Node* ret = create_ast_node_keyword(str_keyword);
    inject_scl(ret);
    return ret;
}

Ast_Node* parse_symbol(char* text, int* index_in_text) {
    // we are now at the first char of the symbol
    char* str_symbol = read_atom(text, index_in_text);
    Ast_Node* ret = create_ast_node_symbol(str_symbol);
    inject_scl(ret);
    return ret;
}

Ast_Node* parse_string(char* text, int* index_in_text) {
    // the first character is the '"'
    ++(*index_in_text);
    ++parser_col;

    // now we are at the first letter, if this is the closing '"' then
    // it's easy
    if (text[*index_in_text] == '"') {
        char* str = new(char);
        *str = '\0';
        Ast_Node* ret = create_ast_node_string(str, 0);
        inject_scl(ret);
        return ret;
    }

    // okay so the first letter was not actually closing the string...
    int string_length = 0;
    while (text[*index_in_text+string_length] != '"' ||
           text[*index_in_text+string_length] == '\\')
    {
        ++string_length;
    }

    // we found the end of the string
    text[*index_in_text+string_length] = '\0';

    char* string = (char*)malloc(string_length*sizeof(char)+1); // plus null char

    if (!unescape_string(text+(*index_in_text))) {
        create_error(
            Error_Type_Unknown_Error,
            create_source_code_location(parser_file, parser_line, parser_col));
        return nullptr;
    }
    strcpy(string, text+(*index_in_text));
    /* manually copy to parse control sequences correctly */
    /* int temp_index = 0; */
    /* while (text+(temp_index+(*index_in_text)) != '\0') { */
    /*     string[temp_index++] = text[temp_index+(*index_in_text)]; */
    /* } */
    /* string[temp_index++] = '\0'; */

    text[*index_in_text+string_length] = '"';

    *index_in_text += string_length +1; // plus one because we want to
                                        // go after the quotes

    Ast_Node* ret = create_ast_node_string(string, string_length);
    inject_scl(ret);
    return ret;
}

Ast_Node* parse_atom(char* text, int* index_in_text) {
    // numbers
    if ((text[*index_in_text] <= 57 &&   // if number
         text[*index_in_text] >= 48)
        ||
        ((text[*index_in_text] == '+' || // or if sign and then number
          text[*index_in_text] == '-')
            &&
         (text[*index_in_text +1] <= 57 &&
          text[*index_in_text +1] >= 48))
        ||
        ((text[*index_in_text] == '.')  // or if . and then number
         &&
         (text[*index_in_text +1] <= 57 &&
          text[*index_in_text +1] >= 48)))
        return parse_number(text, index_in_text);

    // keywords
    if (text[*index_in_text] == ':')
        return parse_keyword(text, index_in_text);

    // strings
    if (text[*index_in_text] == '"')
        return parse_string(text, index_in_text);

    return parse_symbol(text, index_in_text);
}

Ast_Node* parse_expression(char* text, int* index_in_text) {
    if (text[*index_in_text] == '\'') {
        ++(*index_in_text);
        ++parser_col;
        Ast_Node* result;
        if (text[*index_in_text] == '(' || text[*index_in_text] == '\'' ) {
            try {
                result = parse_expression(text, index_in_text);
            }
        } else {
            try {
                result = parse_atom(text, index_in_text);
            }
        }
        return create_ast_node_pair(
            create_ast_node_symbol("quote"),
            create_ast_node_pair(result, create_ast_node_nil()));
    }
    ++(*index_in_text);
    ++parser_col;

    eat_whitespace(text, index_in_text);

    // if there was actually nothing in the list, return nil
    if (text[(*index_in_text)] == ')') {
        ++(*index_in_text);
        ++parser_col;
        return create_ast_node_nil();
    }

    // okay there is something
    Ast_Node* head = new(Ast_Node);
    head->type = Ast_Node_Type_Pair;
    head->value.pair = new(Pair);
    Ast_Node* expression = head;

    while (true) {
        if (text[(*index_in_text)] == '(' || text[(*index_in_text)] == '\'' ) {
            try {
                head->value.pair->first = parse_expression(text, index_in_text);
            }
        } else {
            try {
                head->value.pair->first = parse_atom(text, index_in_text);
            }
        }

        eat_until_code(text, index_in_text);
        if (text[(*index_in_text)] == '\0') {
            create_error(Error_Type_Unexpected_Eof, create_source_code_location(parser_file, parser_line, parser_col));
            return nullptr;
        }


        if (text[(*index_in_text)] == ')') {
            head->value.pair->rest = create_ast_node_nil();
            ++parser_col;
            ++(*index_in_text);
            break;
        } else if (text[(*index_in_text)] == '.') {
            ++parser_col;
            ++(*index_in_text);
            eat_until_code(text, index_in_text);

            if (text[(*index_in_text)] == '(')
                head->value.pair->rest = parse_expression(text, index_in_text);
            else
                head->value.pair->rest = parse_atom(text, index_in_text);

            eat_until_code(text, index_in_text);

            if (text[(*index_in_text)] != ')')
                create_error(Error_Type_Syntax_Error, create_source_code_location(parser_file, parser_line, parser_col));
            ++parser_col;
            ++(*index_in_text);
            break;
        } else {
            head->value.pair->rest = create_ast_node_pair(nullptr, nullptr);
            head = head->value.pair->rest;
        }
    }
    return expression;
}

Ast_Node* parse_single_expression(char* text) {
    parser_file = "stdin";
    parser_line = 1;
    parser_col = 1;

    int index_in_text = 0;
    Ast_Node* result;
    eat_until_code(text, &index_in_text);
    if (text[(index_in_text)] == '\0')
        return create_ast_node_nil();
    if (text[(index_in_text)] == '(' || text[(index_in_text)] == '\'' )
        try {
            result = parse_expression(text, &index_in_text);
        }
    else
        try {
            result = parse_atom(text, &index_in_text);
        }
    eat_until_code(text, &index_in_text);
    if (text[(index_in_text)] == '\0')
        return result;
    create_error(Error_Type_Trailing_Garbage, create_source_code_location(parser_file, parser_line, parser_col));
    return nullptr;
}

Ast_Node_Array_List* parse_program(char* file_name, char* text) {
    parser_file = (char*)malloc(strlen(file_name) * sizeof(char) + 1);
    strcpy(parser_file, file_name);
    parser_line = 1;
    parser_col = 0;

    Ast_Node_Array_List* program = create_Ast_Node_Array_List(16);

    int index_in_text = 0;

    while (text[index_in_text] != '\0') {
        switch (text[index_in_text]) {
        case '(': {
            Ast_Node* parsed;
            try {
                parsed = parse_expression(text, &index_in_text);
            }
            append_to_Ast_Node_Array_List(program, parsed);
        } break;
        case ';':
        case ' ':
        case '\t':
        case '\n':
        case '\r': {
            eat_until_code(text, &index_in_text);
        } break;
        default:
            /* syntax error */
            create_error(Error_Type_Syntax_Error, create_source_code_location(parser_file, parser_line, parser_col));
            return nullptr;
        }
    }
    return program;
}

#undef inject_scl