semos/parser.c

#include "compiler.h"
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void lexer_construct(Lexer* lexer, const char* text, size_t length)
{
    *lexer = (Lexer) {
        .text = text,
        .text_length = length,
        .index = 0,
        .line = 1,
        .col = 1,
        .failed = false,
    };
}

static inline bool is_id_start_char(char c)
{
    return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || c == '_';
}

static inline bool is_id_char(char c)
{
    return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')
        || (c >= '0' && c <= '9') || c == '_';
}

static inline Token skip_comment(Lexer* lexer)
{
    Pos pos = lexer_pos(lexer);
    lexer_step(lexer);
    if (lexer_current(lexer) == '/') {
        while (!lexer_done(lexer) && lexer_current(lexer) != '\n') {
            lexer_step(lexer);
        }
        return lexer_next(lexer);
    } else if (lexer_current(lexer) == '*') {
        lexer_step(lexer);
        char last = '\0';
        while (!lexer_done(lexer)
            && !(last == '*' && lexer_current(lexer) == '/')) {
            last = lexer_current(lexer);
            lexer_step(lexer);
        }
        if (lexer_done(lexer)) {
            lexer->failed = true;
            print_error("lexer: malformed multiline comment", pos);
            return lexer_token(lexer, TokenType_Error, pos);
        }
        return lexer_next(lexer);
    } else {
        lexer->failed = true;
        print_error("lexer: malformed comment", pos);
        return lexer_token(lexer, TokenType_Error, pos);
    }
}

struct MatchIdToTokenTypeCase {
    const char* keyword;
    TokenType token_type;
};

static inline TokenType match_id_to_token_type(
    const char* source, size_t length, struct MatchIdToTokenTypeCase cases[])
{
    for (size_t i = 0; cases[i].keyword != NULL; ++i) {
        if (strlen(cases[i].keyword) <= length
            && strncmp(source, cases[i].keyword, length) == 0) {
            return cases[i].token_type;
        }
    }
    return TokenType_Id;
}

static inline Token lex_id_or_keyword(Lexer* lexer)
{
    Pos pos = lexer_pos(lexer);
    lexer_step(lexer);
    while (!lexer_done(lexer) && is_id_char(lexer_current(lexer))) {
        lexer_step(lexer);
    }
    size_t length = lexer->index - pos.index;
    TokenType token_type
        = match_id_to_token_type(&lexer->text[pos.index], length,
            (struct MatchIdToTokenTypeCase[]) {
                { "not", TokenType_Not },
                { "and", TokenType_And },
                { "or", TokenType_Or },
                { "if", TokenType_If },
                { "else", TokenType_Else },
                { "loop", TokenType_Loop },
                { "let", TokenType_Let },
                { "fn", TokenType_Fn },
                { "return", TokenType_Return },
                { "break", TokenType_Break },
                { NULL, TokenType_Id },
            });
    return lexer_token(lexer, token_type, pos);
}

Token lex_single_char(Lexer* lexer, TokenType token_type)
{
    Pos pos = lexer_pos(lexer);
    lexer_step(lexer);
    return lexer_token(lexer, token_type, pos);
}

Token lex_single_or_double_char(
    Lexer* lexer, TokenType first, char c2, TokenType second)
{
    Pos pos = lexer_pos(lexer);
    lexer_step(lexer);
    if (lexer_done(lexer) || lexer_current(lexer) != c2) {
        return lexer_token(lexer, first, pos);
    }
    lexer_step(lexer);
    return lexer_token(lexer, second, pos);
}

Token lexer_next(Lexer* lexer)
{
    Pos pos = lexer_pos(lexer);
    if (lexer_done(lexer)) {
        return lexer_token(lexer, TokenType_EOF, pos);
    }
    char c = lexer_current(lexer);
    if (c == ' ' || c == '\t' || c == '\n') {
        lexer_step(lexer);
        return lexer_next(lexer);
    }
    if (c == '/') {
        return skip_comment(lexer);
    }
    if (is_id_start_char(c)) {
        return lex_id_or_keyword(lexer);
    }
    if (c >= '1' && c <= '9') {
        lexer_step(lexer);
        while (!lexer_done(lexer) && lexer_current(lexer) >= '0'
            && lexer_current(lexer) <= '9') {
            lexer_step(lexer);
        }
        return lexer_token(lexer, TokenType_Int, pos);
    }
    if (c == '-') {
        lexer_step(lexer);
        if (lexer_current(lexer) == '=') {
            lexer_step(lexer);
            return lexer_token(lexer, TokenType_MinusEqual, pos);
        } else if (lexer_current(lexer) == '>') {
            lexer_step(lexer);
            return lexer_token(lexer, TokenType_MinusGT, pos);
        }
        return lexer_token(lexer, TokenType_Minus, pos);
    }
    switch (c) {
        case '0':
            return lex_single_char(lexer, TokenType_Int);
        case '(':
            return lex_single_char(lexer, TokenType_LParen);
        case ')':
            return lex_single_char(lexer, TokenType_RParen);
        case '{':
            return lex_single_char(lexer, TokenType_LBrace);
        case '}':
            return lex_single_char(lexer, TokenType_RBrace);
        case '[':
            return lex_single_char(lexer, TokenType_LBracket);
        case ']':
            return lex_single_char(lexer, TokenType_RBracket);
        case ',':
            return lex_single_char(lexer, TokenType_Comma);
        case ';':
            return lex_single_char(lexer, TokenType_Semicolon);
        case '+':
            return lex_single_or_double_char(
                lexer, TokenType_Plus, '=', TokenType_PlusEqual);
        case '*':
            return lex_single_or_double_char(
                lexer, TokenType_Asterisk, '=', TokenType_AsteriskEqual);
        case '=':
            return lex_single_or_double_char(
                lexer, TokenType_Equal, '=', TokenType_EqualEqual);
        case '!':
            return lex_single_or_double_char(
                lexer, TokenType_Exclamation, '=', TokenType_ExclamationEqual);
        case '<':
            return lex_single_or_double_char(
                lexer, TokenType_LT, '=', TokenType_LTEqual);
        case '>':
            return lex_single_or_double_char(
                lexer, TokenType_GT, '=', TokenType_GTEqual);
        case '|':
            return lex_single_or_double_char(
                lexer, TokenType_Pipe, '>', TokenType_PipeGT);
    }
    lexer->failed = true;
    print_error("lexer: unrecognized character", pos);
    return lexer_token(lexer, TokenType_Error, pos);
}

bool lexer_failed(const Lexer* lexer) { return lexer->failed; }

Token lexer_token(Lexer* lexer, TokenType token_type, Pos pos)
{
    return (Token) {
        .token_type = token_type,
        .pos = pos,
        .length = lexer->index - pos.index,
    };
}

void lexer_step(Lexer* lexer)
{
    if (lexer_done(lexer)) {
        return;
    }
    lexer->index += 1;
    if (lexer_current(lexer) == '\n') {
        lexer->line += 1;
        lexer->col = 1;
    } else {
        lexer->col += 1;
    }
}

bool lexer_done(const Lexer* lexer)
{
    return lexer->index >= lexer->text_length;
}

char lexer_current(const Lexer* lexer) { return lexer->text[lexer->index]; }

Pos lexer_pos(const Lexer* lexer)
{
    return (Pos) {
        .index = lexer->index,
        .line = lexer->line,
        .col = lexer->col,
    };
}

int ast_node_vec_construct(ASTNodeVec* vec)
{
    const size_t capacity_start = 4;
    *vec = (ASTNodeVec) {
        .data = malloc(capacity_start),
        .length = 0,
        .capacity = capacity_start,
    };
    if (vec->data == NULL) {
        return -1;
    }
    return 0;
}

void ast_node_vec_destroy(ASTNodeVec* vec)
{
    if (vec->data != NULL) {
        free(vec->data);
    }
}

int ast_node_vec_push(ASTNodeVec* vec, ASTNode* item)
{
    if (vec->length + 1 > vec->capacity) {
        vec->capacity *= 2;
        ASTNode** data = realloc(vec->data, vec->capacity);
        if (data == NULL) {
            return -1;
        }
        vec->data = data;
    }
    vec->data[vec->length] = item;
    vec->length += 1;
    return 0;
}

ASTNode* ast_node_new(ASTNodeType node_type, Pos pos, ASTNode spec_init)
{
    ASTNode* node = malloc(sizeof(ASTNode));
    if (node == NULL) {
        return NULL;
    }
    *node = spec_init;
    node->node_type = node_type;
    node->pos = pos;
    return node;
}

void ast_node_free(ASTNode* node)
{
    if (node == NULL) {
        return;
    }
    switch (node->node_type) {
        case ASTNodeType_Error:
            break;
        case ASTNodeType_Id:
            if (node->id_value != NULL) {
                free(node->id_value);
            }
            break;
        case ASTNodeType_Int:
            break;
        case ASTNodeType_Group:
            ast_node_free(node->group_value);
            break;
        case ASTNodeType_Statements:
        case ASTNodeType_Block:
            for (size_t i = 0; i < node->statements.length; ++i) {
                ast_node_free(node->statements.data[i]);
            }
            ast_node_vec_destroy(&node->statements);
            break;
        case ASTNodeType_If:
            ast_node_free(node->if_node.condition);
            ast_node_free(node->if_node.truthy);
            ast_node_free(node->if_node.falsy);
            break;
        case ASTNodeType_Loop:
            ast_node_free(node->loop_node.body);
            break;
        case ASTNodeType_Call:
            ast_node_free(node->call_node.subject);
            for (size_t i = 0; i < node->call_node.args.length; ++i) {
                ast_node_free(node->call_node.args.data[i]);
            }
            ast_node_vec_destroy(&node->call_node.args);
            break;
        case ASTNodeType_Index:
            ast_node_free(node->index_node.subject);
            ast_node_free(node->index_node.value);
            break;
        case ASTNodeType_Unary:
            ast_node_free(node->unary_node.subject);
            break;
        case ASTNodeType_Binary:
            ast_node_free(node->binary_node.left);
            ast_node_free(node->binary_node.right);
            break;
        case ASTNodeType_Assign:
            ast_node_free(node->assign_node.subject);
            ast_node_free(node->assign_node.value);
            break;
        case ASTNodeType_Let:
            ast_node_free(node->let_node.id);
            ast_node_free(node->let_node.value);
            break;
        case ASTNodeType_Break:
            break;
        case ASTNodeType_Fn:
            ast_node_free(node->fn_node.id);
            for (size_t i = 0; i < node->fn_node.params.length; ++i) {
                ast_node_free(node->fn_node.params.data[i]);
            }
            ast_node_vec_destroy(&node->fn_node.params);
            ast_node_free(node->fn_node.body);
            break;
        case ASTNodeType_Return:
            if (node->return_node.value != NULL) {
                ast_node_free(node->return_node.value);
            }
            break;
    }
    free(node);
}

void parser_construct(Parser* parser, const char* text, size_t text_length)
{
    *parser = (Parser) {
        .text = text,
        .text_length = text_length,
        .lexer = { 0 },
        .current = { 0 },
        .failed = false,
    };
    lexer_construct(&parser->lexer, text, text_length);
    parser_step(parser);
}

bool parser_failed(const Parser* parser) { return parser->failed; }

void parser_step(Parser* parser)
{
    parser->current = lexer_next(&parser->lexer);
}

bool parser_done(const Parser* parser)
{
    return parser->current.token_type == TokenType_EOF;
}

ASTNode* parser_parse_statements(Parser* parser)
{
    Pos pos = parser->current.pos;
    ASTNodeVec statements;
    ast_node_vec_construct(&statements);
    while (!parser_done(parser)) {
        ASTNode* statement = parser_parse_statement(parser);
        ast_node_vec_push(&statements, statement);
    }
    return ast_node_new(
        ASTNodeType_Statements, pos, (ASTNode) { .statements = statements });
}

ASTNode* parser_parse_statement(Parser* parser)
{
    if (parser->current.token_type == TokenType_Fn) {
        return parser_parse_fn(parser);
    } else if (parser->current.token_type == TokenType_If) {
        return parser_parse_if(parser);
    } else if (parser->current.token_type == TokenType_Loop) {
        return parser_parse_loop(parser);
    } else {
        ASTNode* statement = parser_parse_single_line_statement(parser);
        if (parser->current.token_type != TokenType_Semicolon) {
            parser->failed = true;
            print_error("parser: expected ';'", parser->current.pos);
        }
        parser_step(parser);
        return statement;
    }
}

ASTNode* parser_parse_fn(Parser* parser)
{
    Pos pos = parser->current.pos;
    parser_step(parser);
    if (parser->current.token_type != TokenType_Id) {
        parser->failed = true;
        print_error("parser: expected 'id'", parser->current.pos);
        return ast_node_new(ASTNodeType_Error, pos, (ASTNode) { 0 });
    }
    ASTNode* id = parser_parse_id(parser);
    if (parser->current.token_type != TokenType_LParen) {
        parser->failed = true;
        print_error("parser: expected '('", parser->current.pos);
        return ast_node_new(ASTNodeType_Error, pos, (ASTNode) { 0 });
    }
    parser_step(parser);
    ASTNodeVec params;
    ast_node_vec_construct(&params);
    if (!parser_done(parser)
        && parser->current.token_type != TokenType_RParen) {
        if (parser->current.token_type != TokenType_Id) {
            parser->failed = true;
            print_error("parser: expected 'id'", parser->current.pos);
            return ast_node_new(ASTNodeType_Error, pos, (ASTNode) { 0 });
        }
        ast_node_vec_push(&params, parser_parse_id(parser));
        while (parser->current.token_type == TokenType_Comma) {
            parser_step(parser);
            if (parser->current.token_type == TokenType_RParen) {
                break;
            }
            if (parser->current.token_type != TokenType_Id) {
                parser->failed = true;
                print_error("parser: expected 'id'", parser->current.pos);
                return ast_node_new(ASTNodeType_Error, pos, (ASTNode) { 0 });
            }
            ast_node_vec_push(&params, parser_parse_id(parser));
        }
    }
    if (parser->current.token_type != TokenType_RParen) {
        parser->failed = true;
        print_error("parser: expected ')'", parser->current.pos);
        return ast_node_new(ASTNodeType_Error, pos, (ASTNode) { 0 });
    }
    parser_step(parser);
    if (parser->current.token_type != TokenType_LBrace) {
        parser->failed = true;
        print_error("parser: expected '{'", parser->current.pos);
        return ast_node_new(ASTNodeType_Error, pos, (ASTNode) { 0 });
    }
    ASTNode* body = parser_parse_block(parser);
    return ast_node_new(ASTNodeType_Fn, pos, (ASTNode) {
        .fn_node = (ASTFnNode) {
            .id = id,
            .params = params,
            .body = body,
        },
    });
}

ASTNode* parser_parse_single_line_statement(Parser* parser)
{
    if (parser->current.token_type == TokenType_Let) {
        return parser_parse_let(parser);
    } else if (parser->current.token_type == TokenType_Return) {
        return parser_parse_return(parser);
    } else if (parser->current.token_type == TokenType_Break) {
        return parser_parse_break(parser);
    } else {
        return parser_parse_assign(parser);
    }
}

ASTNode* parser_parse_let(Parser* parser)
{
    Pos pos = parser->current.pos;
    parser_step(parser);
    if (parser->current.token_type != TokenType_Id) {
        parser->failed = true;
        print_error("parser: expected 'id'", parser->current.pos);
        return ast_node_new(ASTNodeType_Error, pos, (ASTNode) { 0 });
    }
    ASTNode* id = parser_parse_id(parser);
    if (parser->current.token_type != TokenType_Equal) {
        parser->failed = true;
        print_error("parser: expected '='", parser->current.pos);
        return ast_node_new(ASTNodeType_Error, pos, (ASTNode) { 0 });
    }
    parser_step(parser);
    ASTNode* value = parser_parse_expr(parser);
    return ast_node_new(ASTNodeType_Let, pos, (ASTNode) {
        .let_node = (ASTLetNode) {
            .id = id,
            .value = value,
        },
    });
}

ASTNode* parser_parse_return(Parser* parser)
{
    Pos pos = parser->current.pos;
    parser_step(parser);
    ASTNode* value = NULL;
    if (parser->current.token_type != TokenType_Semicolon) {
        value = parser_parse_expr(parser);
    }
    return ast_node_new(ASTNodeType_Return, pos, (ASTNode) {
        .return_node = (ASTReturnNode) {
            .value = value,
        },
    });
}

ASTNode* parser_parse_break(Parser* parser)
{
    Pos pos = parser->current.pos;
    parser_step(parser);
    return ast_node_new(ASTNodeType_Return, pos, (ASTNode) { 0 });
}

ASTNode* parser_parse_assign(Parser* parser)
{
    Pos pos = parser->current.pos;
    ASTNode* subject = parser_parse_expr(parser);
    int assign_type = -1;
    if (parser->current.token_type == TokenType_Equal) {
        assign_type = AssignType_Assign;
    } else if (parser->current.token_type == TokenType_PlusEqual) {
        assign_type = AssignType_Add;
    } else if (parser->current.token_type == TokenType_MinusEqual) {
        assign_type = AssignType_Subtract;
    } else if (parser->current.token_type == TokenType_AsteriskEqual) {
        assign_type = AssignType_Multiply;
    }
    if (assign_type == -1) {
        return subject;
    }
    parser_step(parser);
    return ast_node_new(ASTNodeType_Assign, pos, (ASTNode) {
        .assign_node = (ASTAssignNode) {
            .assign_type = (AssignType)assign_type,
            .subject = subject,
            .value = parser_parse_expr(parser),
        },
    });
}

ASTNode* parser_parse_expr(Parser* parser) { return parser_parse_or(parser); }

static inline ASTNode* binary_node(
    Pos pos, BinaryType binary_type, ASTNode* left, ASTNode* right)
{
    return ast_node_new(ASTNodeType_Binary, pos, (ASTNode) {
        .binary_node = (ASTBinaryNode) {
            .binary_type = binary_type,
            .left = left,
            .right = right,
        },
    });
}

ASTNode* parser_parse_or(Parser* parser)
{
    Pos pos = parser->current.pos;
    ASTNode* left = parser_parse_and(parser);
    while (parser->current.token_type == TokenType_Or) {
        parser_step(parser);
        left = binary_node(pos, BinaryType_Or, left, parser_parse_and(parser));
    }
    return left;
}

ASTNode* parser_parse_and(Parser* parser)
{
    Pos pos = parser->current.pos;
    ASTNode* left = parser_parse_equality(parser);
    while (parser->current.token_type == TokenType_And) {
        parser_step(parser);
        left = binary_node(
            pos, BinaryType_And, left, parser_parse_equality(parser));
    }
    return left;
}

ASTNode* parser_parse_equality(Parser* parser)
{
    Pos pos = parser->current.pos;
    ASTNode* left = parser_parse_comparison(parser);
    if (parser->current.token_type == TokenType_EqualEqual) {
        parser_step(parser);
        return binary_node(
            pos, BinaryType_EE, left, parser_parse_comparison(parser));
    } else if (parser->current.token_type == TokenType_ExclamationEqual) {
        parser_step(parser);
        return binary_node(
            pos, BinaryType_NE, left, parser_parse_comparison(parser));
    } else {
        return left;
    }
}

ASTNode* parser_parse_comparison(Parser* parser)
{
    Pos pos = parser->current.pos;
    ASTNode* left = parser_parse_term(parser);
    while (!parser_done(parser)) {
        if (parser->current.token_type == TokenType_LT) {
            parser_step(parser);
            return binary_node(
                pos, BinaryType_LT, left, parser_parse_term(parser));
        } else if (parser->current.token_type == TokenType_LTEqual) {
            parser_step(parser);
            return binary_node(
                pos, BinaryType_LTE, left, parser_parse_term(parser));
        } else if (parser->current.token_type == TokenType_GT) {
            parser_step(parser);
            return binary_node(
                pos, BinaryType_GT, left, parser_parse_term(parser));
        } else if (parser->current.token_type == TokenType_GTEqual) {
            parser_step(parser);
            return binary_node(
                pos, BinaryType_GTE, left, parser_parse_term(parser));
        } else {
            break;
        }
    }
    return left;
}

ASTNode* parser_parse_term(Parser* parser)
{
    Pos pos = parser->current.pos;
    ASTNode* left = parser_parse_factor(parser);
    while (!parser_done(parser)) {
        if (parser->current.token_type == TokenType_Plus) {
            parser_step(parser);
            return binary_node(
                pos, BinaryType_Add, left, parser_parse_factor(parser));
        } else if (parser->current.token_type == TokenType_Minus) {
            parser_step(parser);
            return binary_node(
                pos, BinaryType_Subtract, left, parser_parse_factor(parser));
        } else {
            break;
        }
    }
    return left;
}

ASTNode* parser_parse_factor(Parser* parser)
{
    Pos pos = parser->current.pos;
    ASTNode* left = parser_parse_unary(parser);
    while (!parser_done(parser)) {
        if (parser->current.token_type == TokenType_Asterisk) {
            parser_step(parser);
            return binary_node(
                pos, BinaryType_Multiply, left, parser_parse_unary(parser));
        } else {
            break;
        }
    }
    return left;
}

ASTNode* parser_parse_unary(Parser* parser)
{
    Pos pos = parser->current.pos;
    if (parser->current.token_type == TokenType_Not) {
        parser_step(parser);
        return ast_node_new(ASTNodeType_Unary, pos, (ASTNode) {
            .unary_node = (ASTUnaryNode) {
                .unary_type = UnaryType_Not,
                .subject = parser_parse_unary(parser),
            },
        });
    } else if (parser->current.token_type == TokenType_Minus) {
        parser_step(parser);
        return ast_node_new(ASTNodeType_Unary, pos, (ASTNode) {
            .unary_node = (ASTUnaryNode) {
                .unary_type = UnaryType_Negate,
                .subject = parser_parse_unary(parser),
            },
        });
    } else {
        return parser_parse_index_call(parser);
    }
}

ASTNode* parser_parse_index_call(Parser* parser)
{
    Pos pos = parser->current.pos;
    ASTNode* subject = parser_parse_operand(parser);
    while (!parser_done(parser)) {
        if (parser->current.token_type == TokenType_LParen) {
            parser_step(parser);
            ASTNodeVec args;
            ast_node_vec_construct(&args);
            if (!parser_done(parser)
                && parser->current.token_type != TokenType_RParen) {
                ast_node_vec_push(&args, parser_parse_expr(parser));
                while (parser->current.token_type == TokenType_Comma) {
                    parser_step(parser);
                    if (parser->current.token_type == TokenType_RParen) {
                        break;
                    }
                    ast_node_vec_push(&args, parser_parse_expr(parser));
                }
            }
            if (parser->current.token_type != TokenType_RParen) {
                parser->failed = true;
                print_error("parser: expected ')'", parser->current.pos);
                return ast_node_new(ASTNodeType_Error, pos, (ASTNode) { 0 });
            }
            parser_step(parser);
            subject = ast_node_new(ASTNodeType_Call, pos, (ASTNode) {
                .call_node = (ASTCallNode) {
                    .subject = subject,
                    .args = args,
                },
            });
        } else if (parser->current.token_type == TokenType_LBracket) {
            parser_step(parser);
            ASTNode* value = parser_parse_expr(parser);
            if (parser->current.token_type != TokenType_RBracket) {
                parser->failed = true;
                print_error("parser: expected ']'", parser->current.pos);
                return ast_node_new(ASTNodeType_Error, pos, (ASTNode) { 0 });
            }
            parser_step(parser);
            subject = ast_node_new(ASTNodeType_Index, pos, (ASTNode) {
                .index_node = (ASTIndexNode) {
                    .subject = subject,
                    .value = value,
                },
            });
        } else {
            break;
        }
    }
    return subject;
}

ASTNode* parser_parse_operand(Parser* parser)
{
    Pos pos = parser->current.pos;
    switch (parser->current.token_type) {
        case TokenType_Error:
            return ast_node_new(ASTNodeType_Error, pos, (ASTNode) { 0 });
        case TokenType_Id:
            return parser_parse_id(parser);
        case TokenType_Int:
            return parser_parse_int(parser);
        case TokenType_LParen:
            return parser_parse_group(parser);
        case TokenType_LBrace:
            return parser_parse_block(parser);
        case TokenType_If:
            return parser_parse_if(parser);
        case TokenType_Loop:
            return parser_parse_loop(parser);
        default:
            parser->failed = true;
            print_error("parser: expected operand", pos);
            return ast_node_new(ASTNodeType_Error, pos, (ASTNode) { 0 });
    }
}

ASTNode* parser_parse_id(Parser* parser)
{
    Pos pos = parser->current.pos;
    char* value = malloc(parser->current.length + 1);
    value[parser->current.length] = '\0';
    strncpy(value, &parser->text[parser->current.pos.index],
        parser->current.length);
    parser_step(parser);
    return ast_node_new(ASTNodeType_Id, pos, (ASTNode) { .id_value = value });
}

ASTNode* parser_parse_int(Parser* parser)
{
    Pos pos = parser->current.pos;
    int value = (int)strtol(&parser->text[parser->current.length], NULL, 10);
    parser_step(parser);
    return ast_node_new(ASTNodeType_Int, pos, (ASTNode) { .int_value = value });
}

ASTNode* parser_parse_group(Parser* parser)
{
    Pos pos = parser->current.pos;
    parser_step(parser);
    ASTNode* expr = parser_parse_expr(parser);
    if (parser->current.token_type != TokenType_RParen) {
        parser->failed = true;
        print_error("parser: expected ')'", parser->current.pos);
        return ast_node_new(ASTNodeType_Error, pos, (ASTNode) { 0 });
    }
    parser_step(parser);
    return ast_node_new(ASTNodeType_Group, pos,
        (ASTNode) {
            .group_value = expr,
        });
}

ASTNode* parser_parse_block(Parser* parser)
{
    Pos pos = parser->current.pos;
    parser_step(parser);
    ASTNodeVec statements;
    ast_node_vec_construct(&statements);
    while (!parser_done(parser)
        && parser->current.token_type != TokenType_RBrace) {
        ASTNode* statement = parser_parse_statement(parser);
        ast_node_vec_push(&statements, statement);
    }
    if (parser->current.token_type != TokenType_RBrace) {
        parser->failed = true;
        print_error("parser: expected '}'", parser->current.pos);
        return ast_node_new(ASTNodeType_Error, pos, (ASTNode) { 0 });
    }
    parser_step(parser);
    return ast_node_new(
        ASTNodeType_Block, pos, (ASTNode) { .statements = statements });
}

ASTNode* parser_parse_if(Parser* parser)
{
    Pos pos = parser->current.pos;
    parser_step(parser);
    ASTNode* condition = parser_parse_expr(parser);
    if (parser->current.token_type != TokenType_LBrace) {
        parser->failed = true;
        print_error("parser: expected '{'", parser->current.pos);
        return ast_node_new(ASTNodeType_Error, pos, (ASTNode) { 0 });
    }
    ASTNode* truthy = parser_parse_block(parser);
    ASTNode* falsy = NULL;
    if (parser->current.token_type == TokenType_Else) {
        parser_step(parser);
        if (parser->current.token_type != TokenType_LBrace) {
            parser->failed = true;
            print_error("parser: expected '{'", parser->current.pos);
            return ast_node_new(ASTNodeType_Error, pos, (ASTNode) { 0 });
        }
        falsy = parser_parse_block(parser);
    }
    return ast_node_new(ASTNodeType_If, pos, (ASTNode) {
        .if_node = (ASTIfNode) {
            .condition = condition,
            .truthy = truthy,
            .falsy = falsy,
        },
    });
}

ASTNode* parser_parse_loop(Parser* parser)
{
    Pos pos = parser->current.pos;
    parser_step(parser);
    if (parser->current.token_type != TokenType_RBrace) {
        parser->failed = true;
        print_error("parser: expected '}'", parser->current.pos);
        return ast_node_new(ASTNodeType_Error, pos, (ASTNode) { 0 });
    }
    ASTNode* body = parser_parse_block(parser);
    return ast_node_new(ASTNodeType_Loop, pos, (ASTNode) {
        .loop_node = (ASTLoopNode) { 
            .body = body,
        },
    });
}