mirror of
https://github.com/PashaBibko/LX.git
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304 lines
9.4 KiB
C++
304 lines
9.4 KiB
C++
#include <Parser.h>
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#include <Util.h>
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#include <AST.h>
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#include <iostream>
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namespace LX
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{
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// Util function for working out if a token is a two sided operator //
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static bool IsTwoSidedOperator(Token::TokenType t)
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{
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switch (t)
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{
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case Token::ADD:
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case Token::SUB:
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case Token::DIV:
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case Token::MUL:
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return true;
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default:
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return false;
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}
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}
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// Local struct so everything can be public //
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struct Parser
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{
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// Passes constructor args to members //
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Parser(std::vector<Token>& _tokens, std::ofstream* _log)
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: tokens(_tokens), log(_log), index(0), len(_tokens.size()), scopeDepth(0)
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{}
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// Tokens created by the lexer //
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std::vector<Token>& tokens;
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// Log to output to (can be null) //
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std::ofstream* log;
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// Length of the the token vector //
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const size_t len;
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// Current index within the token vector //
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size_t index;
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// Current scope depth //
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size_t scopeDepth;
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};
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// Base of the call stack to handle the simplest of tokens //
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static std::unique_ptr<AST::Node> ParsePrimary(Parser& p)
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{
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// There are lots of possible token's that can be here so a switch is used //
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switch (p.tokens[p.index].type)
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{
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// Number literals just require them to be turned into an AST node //
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// Note: Number literals are stored as strings because i'm a masochist //
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case Token::NUMBER_LITERAL:
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return std::make_unique<AST::NumberLiteral>(p.tokens[p.index++].GetContents());
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// If an Identifier has got here it means a variable is being accessed //
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case Token::IDENTIFIER:
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return std::make_unique<AST::VariableAccess>(p.tokens[p.index++].GetContents());
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// TODO: Fix this //
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case Token::OPEN_BRACKET:
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p.scopeDepth++;
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p.index++;
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return nullptr;
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// TODO: Fix this //
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case Token::CLOSE_BRACE:
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ThrowIf<UnexpectedToken>(p.scopeDepth == 0, Token::UNDEFINED, "need a different error", p.tokens[p.index]);
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p.scopeDepth--;
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p.index++;
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return nullptr;
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// Returns nullptr, the parsing function that recives that value will decide if that is valid //
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default:
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p.index++;
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return nullptr;
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}
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}
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// Handles operations, if it is not currently at an operation goes to ParsePrimary //
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static std::unique_ptr<AST::Node> ParseOperation(Parser& p)
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{
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// Checks if the next token is an operator //
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// TODO: Add more than just add //
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if (p.index + 1 < p.len) [[likely]]
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{
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if (IsTwoSidedOperator(p.tokens[p.index + 1].type))
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{
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// Parses the left hand side of the operation //
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std::unique_ptr<AST::Node> lhs = ParsePrimary(p);
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ThrowIf<UnexpectedToken>(lhs == nullptr, Token::UNDEFINED, "value", p.tokens[p.index - 1]);
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// Stores the operator to pass into the AST node //
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Token::TokenType op = p.tokens[p.index].type;
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p.index++;
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// Parses the right hand of the operation //
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std::unique_ptr<AST::Node> rhs = ParseOperation(p);
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ThrowIf<UnexpectedToken>(rhs == nullptr, Token::UNDEFINED, "value", p.tokens[p.index - 1]);
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// Returns an AST node as all of the components combined together //
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return std::make_unique<AST::Operation>(std::move(lhs), op, std::move(rhs));
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}
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}
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// Else goes down the call stack //
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return ParsePrimary(p);
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}
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// Handles return statements, if not calls ParseOperation //
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static std::unique_ptr<AST::Node> ParseReturn(Parser& p)
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{
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// Checks if the current token is a return //
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if (p.tokens[p.index].type == Token::RETURN)
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{
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// If so it adds an AST node with the value being returned //
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// Does not mind if this returns nullptr as that just means nothing was returned //
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p.index++;
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return std::make_unique<AST::ReturnStatement>(ParseOperation(p));
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}
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// Else goes down the call stack //
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return ParseOperation(p);
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}
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// Handles variable declarations, if not calls ParseReturn //
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static std::unique_ptr<AST::Node> ParseVarDeclaration(Parser& p)
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{
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// Checks if the current token is a declaration //
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if (p.tokens[p.index].type == Token::INT_DEC)
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{
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// Skips over the dec token //
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p.index++;
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// Checks for the variable name //
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ThrowIf<UnexpectedToken>(p.tokens[p.index].type != Token::IDENTIFIER, Token::IDENTIFIER, "", p.tokens[p.index]);
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std::string name = p.tokens[p.index].GetContents();
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p.index++; // <- Goes over the identifier token
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// Returns the declaration if there is no default assignment to the variable //
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if (p.tokens[p.index].type != Token::ASSIGN)
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{
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// Creates the variable name from the contents of the token and returns it //
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return std::make_unique<AST::VariableDeclaration>(name);
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}
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p.index++; // Skips over Token::ASSIGN
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// Gets the value to be assigned to the variable //
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std::unique_ptr<AST::Node> defaultVal = ParsePrimary(p);
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ThrowIf<UnexpectedToken>(defaultVal.get() == nullptr, Token::UNDEFINED, "value", p.tokens[p.index - 1]);
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return std::make_unique<AST::VariableDeclaration>(name);
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}
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// Else goes down the call stack //
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return ParseReturn(p);
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}
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// Handles variable assignments, if not calls ParseVarDeclaration //
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static std::unique_ptr<AST::Node> ParseVarAssignment(Parser& p)
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{
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// Checks if the next token is an equals //
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if (p.index + 1 < p.len) [[likely]]
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{
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if (p.tokens[p.index + 1].type == Token::ASSIGN)
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{
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// Gets the variable that is being assigned too //
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ThrowIf<UnexpectedToken>(p.tokens[p.index].type != Token::IDENTIFIER, Token::IDENTIFIER, "", p.tokens[p.index]);
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std::string name = p.tokens[p.index].GetContents();
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// Skips over the assign token and name of the variable //
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p.index = p.index + 2;
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// Gets the value that is being assigned //
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std::unique_ptr<AST::Node> value = ParseOperation(p);
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// Returns an AST node of the variable assignment with it's name and value //
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return std::make_unique<AST::VariableAssignment>(name, std::move(value));
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}
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}
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// Else goes down the call stack //
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return ParseVarDeclaration(p);
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}
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// Helper function to call the top of the Parse-Call-Stack //
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static inline std::unique_ptr<AST::Node> Parse(Parser& p)
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{
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// Parses the current token //
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std::unique_ptr<AST::Node> out = ParseVarAssignment(p);
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// Checks it is valid before returning //
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ThrowIf<UnexpectedToken>(out == nullptr, Token::UNDEFINED, "top level statement", p.tokens[p.index - 1]);
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return out;
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}
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// Turns the tokens of a file into it's abstract syntax tree equivalent //
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FileAST TurnTokensIntoAbstractSyntaxTree(std::vector<Token>& tokens, std::ofstream* log)
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{
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// Logs the start of the parsing
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SafeLog(log, LOG_BREAK, "Started parsing tokens", LOG_BREAK);
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// Creates the output storer and the parser //
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FileAST output;
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Parser p(tokens, log);
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// Loops over the tokens and calls the correct parsing function //
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// Which depends on their type and current state of the parser //
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while (p.index < p.len)
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{
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switch (p.tokens[p.index].type)
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{
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case Token::FUNCTION:
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{
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// Skips over function token //
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p.index++;
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// Pushes a new function to the vector and gets a reference to it for adding the body //
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output.functions.emplace_back();
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FunctionDefinition& func = output.functions.back();
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// Assigns the function name //
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ThrowIf<UnexpectedToken>(p.tokens[p.index].type != Token::IDENTIFIER, Token::IDENTIFIER, "", p.tokens[p.index]);
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func.name = p.tokens[p.index++].GetContents();
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// Checks for opening paren '(' //
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ThrowIf<UnexpectedToken>(p.tokens[p.index].type != Token::OPEN_PAREN, Token::OPEN_PAREN, "", p.tokens[p.index]);
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p.index++;
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// Loops over all the arguments of the function //
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// TODO: Do something with the parameters
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while (p.index < p.len && (p.tokens[p.index].type == Token::CLOSE_PAREN) == false)
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{
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p.index++;
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}
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// Skips over close bracket //
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p.index++;
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// Checks for opening bracket '{' //
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ThrowIf<UnexpectedToken>(p.tokens[p.index].type != Token::OPEN_BRACKET, Token::OPEN_BRACKET, "", p.tokens[p.index]);
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p.index++;
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// Loops over the body until it reaches the end //
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while (p.index < p.len && (p.tokens[p.index].type == Token::CLOSE_BRACKET && p.scopeDepth == 0) == false)
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{
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// Actually parses the function //
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std::unique_ptr<AST::Node> node = Parse(p);
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// Expands the node if it contains multiple //
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if (node->m_Type == AST::Node::MULTI_NODE)
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{
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for (std::unique_ptr<AST::Node>& containedNode : ((AST::MultiNode*)node.get())->nodes)
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{
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// Logs the node to the log //
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if (log != nullptr) { node->Log(log, 0); }
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// Adds it to the vector //
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func.body.push_back(std::move(containedNode));
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}
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}
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// Else adds the singular node to the vector //
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else
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{
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// Logs the node to the log //
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if (log != nullptr) { node->Log(log, 0); }
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// Adds it to the vector //
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func.body.push_back(std::move(node));
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}
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}
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// Skips over closing bracket //
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p.index++;
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// Goes to the next iteration of the loop //
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continue;
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}
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// Lets the user know there is an error //
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// TODO: Makes this error actually output useful information //
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default:
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std::cout << "UNKNOWN TOKEN FOUND: " << ToString(p.tokens[p.index].type) << std::endl;
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return output;
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}
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}
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// Logs that AST has finished parsing //
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// TODO: Make this output the AST in a human-readable form //
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SafeLog(log, "AST length: ", output.functions[0].body.size());
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// Returns the output and shrinks all uneccesarry allocated memory
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output.functions.shrink_to_fit();
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return output;
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}
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}
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