Erythro/src/Statements.c

/*************/
/*GEMWIRE    */
/*    ERYTHRO*/
/*************/

#include <Defs.h>
#include <Data.h>
#include <stdbool.h>

static int ReadParameters() {
    int TokenType, ParamCount = 0;

    while(CurrentToken.type != LI_RPARE) {
        TokenType = ParseOptionalPointer();
        VerifyToken(TY_IDENTIFIER, "identifier");

        BeginVariableDeclaration(TokenType, SC_PARAM, true);
        ParamCount++;

        switch(CurrentToken.type) {
            case LI_COM: 
                Tokenise(&CurrentToken);
                break;
            case LI_RPARE:
                break;
            default:     
                DieDecimal("Unexpected token in parameter", CurrentToken.type);
        }
    }

    return ParamCount;
}

/*
 * Handles the declaration of a type of a variable.
 *  int newVar;
 * 
 * It verifies that we have the `int` keyword followed by a
 *  unique, non-keyword identifier.
 * 
 * It then stores this variable into the symbol table.
 * 
 * //TODO: Assemble this into the symbol table.
 * //TODO: int i = 5;
 * 
 */
void BeginVariableDeclaration(int Type, int Scope, bool isParameter) {
    int ID;
    printf("type: %s\n", TypeNames[Type]);

    if(CurrentToken.type == LI_LBRAS) {
        Tokenise(&CurrentToken);
        //Type = Type - 2;
        if(CurrentToken.type == LI_INT) {
            printf("Adding array %s that is %d x %s.\r\n", CurrentIdentifier, CurrentToken.value, TypeNames[Type]);
            if(Scope == SC_LOCAL)
                Die("Local arrays are not supported");
            else
                AddSymbol(CurrentIdentifier, PointerTo(Type), ST_ARR, Scope, 0, CurrentToken.value);
        }

        Tokenise(&CurrentToken);
        VerifyToken(LI_RBRAS, "]");
    } else {
        printf("Adding var %s that is a %s\r\n", CurrentIdentifier, TypeNames[Type]);
        if(Scope == SC_LOCAL) {
            if(AddSymbol(CurrentIdentifier, Type, ST_VAR, Scope, 0, 1) == -1)
                Die("Illegal state: Identical locals in current function");
        } else {
            AddSymbol(CurrentIdentifier, Type, ST_VAR, Scope, 0, 1);
        }
    }

    //VerifyToken(LI_SEMIC, ";");
}

struct ASTNode* ParseFunction(int Type) {
    struct ASTNode* Tree;
    struct ASTNode* FinalStatement;
    int SymbolSlot, BreakLabel, ParamCount;

    BreakLabel = NewLabel();
    printf("\nIdentified function %s of return type %s, end label %d\n", CurrentIdentifier, TypeNames[Type], BreakLabel);

    SymbolSlot = AddSymbol(CurrentIdentifier, Type, ST_FUNC, SC_GLOBAL, BreakLabel, 1);
    CurrentFunction = SymbolSlot;

    AsNewStackFrame();

    VerifyToken(LI_LPARE, "(");
    ParamCount = ReadParameters();
    Symbols[SymbolSlot].Length = ParamCount;
    VerifyToken(LI_RPARE, ")");

    Tree = ParseCompound();

    if(Type != RET_VOID) {
        // Functions with one statement have no composite node, so we have to check
        FinalStatement = (Tree->Operation == OP_COMP) ? Tree->Right : Tree;

        if(FinalStatement == NULL || FinalStatement->Operation != OP_RET) {
            Die("Function with non-void type does not return");
        }

    }

    return ConstructASTBranch(OP_FUNC, Tree->ExprType, Tree, SymbolSlot);
}

/*
 *  Handles the logic for return.
 *  //TODO: No brackets
 *  //TODO: Type inference
 * 
 * 
 */

struct ASTNode* ReturnStatement() {
    struct ASTNode* Tree;
    int ReturnType, FunctionType;


    if(Symbols[CurrentFunction].Type == RET_VOID)
        Die("Attempt to return from void function");
    
    VerifyToken(KW_RETURN, "return");

    VerifyToken(LI_LPARE, "("); // TODO: Make optional! Reject?

    Tree = ParsePrecedenceASTNode(0);

    /*
    ReturnType = Tree->ExprType;
    FunctionType = Symbols[CurrentFunction].Type;
    */

    Tree = MutateType(Tree, Symbols[CurrentFunction].Type, 0);
    if(Tree == NULL)
        Die("Returning a value of incorrect type for function");
    
    /*
    if(ReturnType)
        Tree = ConstructASTBranch(ReturnType, FunctionType, Tree, 0);
    */

    Tree = ConstructASTBranch(OP_RET, RET_NONE, Tree, 0);

    printf("\t\tReturning from function %s\n", Symbols[CurrentFunction].Name);

    VerifyToken(LI_RPARE, ")"); // TODO: OPTIONALISE!

    return Tree;
}

/*
 * Handles Identifiers.
 * 
 * This is called for any of:
 *  - Calling a function
 *  - Assigning an lvalue variable
 *  - Performing arithmetic on a variable
 *  - Performing arithmetic with the return values of function calls
 * 
 * For the case where you're assigning an l-value;
 *  You can assign with another assignment,
 *   a statement, a function or a literal.
 * 
 */

/*
struct ASTNode* ParseIdentifier() {
    struct ASTNode* Left, *Right, *Tree;
    int LeftType, RightType;
    int ID;

    VerifyToken(TY_IDENTIFIER, "ident");

    printf("\t\tAfter parsing, the identifier name is %s, id %d in the symbol table.\n", CurrentIdentifier, FindSymbol(CurrentIdentifier));

    if(CurrentToken.type == LI_LPARE)
        return CallFunction();

    if((ID = FindSymbol(CurrentIdentifier)) == -1) {
        printf("Symbol %s not in table. Table contents: %s, %s\n", CurrentIdentifier, Symbols[0].Name, Symbols[1].Name);
        DieMessage("Undeclared Variable ", CurrentIdentifier);
    }
    Right = ConstructASTLeaf(LV_IDENT, Symbols[ID].Type, ID);

    VerifyToken(LI_EQUAL, "=");

    Left = ParsePrecedenceASTNode(0);

    LeftType = Left->ExprType;
    RightType = Right->ExprType;

    Left = MutateType(Left, RightType, 0);
    if(!Left)
        Die("Incompatible types in assignment");
    
    if(LeftType)
        Left = ConstructASTBranch(LeftType, Right->ExprType, Left, 0);

    Tree = ConstructASTNode(OP_ASSIGN, RET_INT, Left, NULL, Right, 0);

    return Tree;
}*/

struct ASTNode* IfStatement() {
    struct ASTNode* Condition, *True, *False = NULL;

    VerifyToken(KW_IF, "if");
    VerifyToken(LI_LPARE, "(");

    Condition = ParsePrecedenceASTNode(0);

    // Limit if(x) to =? != < > <= => 
    // No null checking, no arithmetic, no functions.
    // TODO: this
    if(Condition->Operation < OP_EQUAL || Condition->Operation > OP_GREATE)
        Condition = ConstructASTBranch(OP_BOOLCONV, Condition->ExprType, Condition, 0);
    
    VerifyToken(LI_RPARE, ")");

    True = ParseCompound();

    if(CurrentToken.type == KW_ELSE) {
        Tokenise(&CurrentToken);
        False = ParseCompound();
    }

    return ConstructASTNode(OP_IF, RET_NONE, Condition, True, False, 0);
}

struct ASTNode* WhileStatement() {
    struct ASTNode* Condition, *Body;

    VerifyToken(KW_WHILE, "while");
    VerifyToken(LI_LPARE, "(");

    Condition = ParsePrecedenceASTNode(0);


    if(Condition->Operation < OP_EQUAL || Condition->Operation > OP_GREATE)
        Condition = ConstructASTBranch(OP_BOOLCONV, Condition->ExprType, Condition, 0);
    
    VerifyToken(LI_RPARE, ")");

    Body = ParseCompound();

    return ConstructASTNode(OP_LOOP, RET_NONE, Condition, NULL, Body, 0);
}

struct ASTNode* ForStatement() {

    // for (preop; condition; postop) {
    //    body
    //}

    struct ASTNode* Condition, *Body;
    struct ASTNode* Preop, *Postop;

    struct ASTNode* Tree;

    VerifyToken(KW_FOR, "for");
    VerifyToken(LI_LPARE, "(");

    Preop = ParseStatement();
    VerifyToken(LI_SEMIC, ";");

    Condition = ParsePrecedenceASTNode(0);

    if(Condition->Operation < OP_EQUAL || Condition->Operation > OP_GREATE)
        Condition = ConstructASTBranch(OP_BOOLCONV, Condition->ExprType, Condition, 0);

    VerifyToken(LI_SEMIC, ";");

    Postop = ParseStatement();
    VerifyToken(LI_RPARE, ")");

    Body = ParseCompound();

    // We need to be able to skip over the body and the postop, so we group them together.
    Tree = ConstructASTNode(OP_COMP, RET_NONE, Body, NULL, Postop, 0);
    // We need to be able to jump to the top of the condition and fall through to the body,
    //  so we group it with the last block
    Tree = ConstructASTNode(OP_LOOP, RET_NONE, Condition, NULL, Tree, 0);

    // We need to append the postop to the loop, to form the final for loop
    return ConstructASTNode(OP_COMP, RET_NONE, Preop, NULL, Tree, 0);
}

struct ASTNode* PrintStatement(void) {
    struct ASTNode* Tree;
    int LeftType, RightType;

    VerifyToken(KW_PRINT, "print");

    Tree = ParsePrecedenceASTNode(0);

    LeftType = RET_INT;
    RightType = Tree->ExprType;

    Tree = MutateType(Tree, RightType, 0);
    if(!Tree)
        DieDecimal("Attempting to print an invalid type:", RightType);
    
    if(RightType)
        Tree = ConstructASTBranch(RightType, RET_INT, Tree, 0);
    
    Tree = ConstructASTBranch(OP_PRINT, RET_NONE, Tree, 0);

    //ParseAST(Tree);

    return Tree;
   
}

struct ASTNode* PostfixStatement() {
    struct ASTNode* Tree;
    int ID;

    Tokenise(&CurrentToken);
    
    // If we get here, we're one of three things:
    //  - Function
    //  - Array
    //  - Variable

    if(CurrentToken.type == LI_LPARE)
        return CallFunction();
    
    if(CurrentToken.type == LI_LBRAS)
        return AccessArray();
    
    // If we get here, we must be a variable.
    // There's no guarantees that the variable is in
    //  the symbol table, though.

    ID = FindSymbol(CurrentIdentifier);
    if(ID == -1 || Symbols[ID].Structure != ST_VAR)
        DieMessage("Unknown Variable", CurrentIdentifier);

    // Here we check for postincrement and postdecrement.

    switch(CurrentToken.type) {
        case PPMM_PLUS:
            Tokenise(&CurrentToken);
            Tree = ConstructASTLeaf(OP_POSTINC, Symbols[ID].Type, ID);
            break;
        case PPMM_MINUS:
            Tokenise(&CurrentToken);
            Tree = ConstructASTLeaf(OP_POSTDEC, Symbols[ID].Type, ID);
            break;
        default:
            Tree = ConstructASTLeaf(REF_IDENT, Symbols[ID].Type, ID);
    }

    return Tree;
    
}

struct ASTNode* PrefixStatement() {
    struct ASTNode* Tree;

    switch (CurrentToken.type) {
        case BOOL_INVERT:
            Tokenise(&CurrentToken);
            Tree = PrefixStatement();
            Tree->RVal = 1;
            Tree = ConstructASTBranch(OP_BOOLNOT, Tree->ExprType, Tree, 0);
            break;

        case BIT_NOT:
            Tokenise(&CurrentToken);
            Tree = PrefixStatement();
            Tree->RVal = 1;
            Tree = ConstructASTBranch(OP_BITNOT, Tree->ExprType, Tree, 0);
            break;
        
        case AR_MINUS:
            Tokenise(&CurrentToken);
            Tree = PrefixStatement();
            
            Tree = ConstructASTBranch(OP_NEGATE, Tree->ExprType, Tree, 0);
            break;

        case PPMM_PLUS:
            Tokenise(&CurrentToken);
            Tree = PrefixStatement();

            if(Tree->Operation != REF_IDENT)
                Die("++ not followed by identifier");
            Tree = ConstructASTBranch(OP_PREINC, Tree->ExprType, Tree, 0);
            break;

        case PPMM_MINUS:
            Tokenise(&CurrentToken);
            Tree = PrefixStatement();

            if(Tree->Operation != REF_IDENT)
                Die("-- not followed by identifier");
            
            Tree = ConstructASTBranch(OP_PREDEC, Tree->ExprType, Tree, 0);
            break;

        case BIT_AND:
            Tokenise(&CurrentToken);

            // To allow things like:
            // x = &&y;
            // We need to recursively parse prefixes;
            Tree = PrefixStatement();

            if(Tree->Operation != REF_IDENT) 
                Die("& must be followed by another & or an identifier.");

            Tree->Operation = OP_ADDRESS;
            Tree->ExprType = PointerTo(Tree->ExprType);
            break;
        case AR_STAR:
            Tokenise(&CurrentToken);

            Tree = PrefixStatement();

            if(Tree->Operation != REF_IDENT && Tree->Operation != OP_DEREF)
                Die("* must be followed by another * or an identifier.");

            Tree = ConstructASTBranch(OP_DEREF, ValueAt(Tree->ExprType), Tree, 0);
            break;

        default:
            Tree = ParsePrimary();
            
    }

    return Tree;
}