/* vim: set ts=4 sw=4 tw=99 et:

 *

 * Copyright (C) 2012 David Anderson

 *

 * This file is part of SourcePawn.

 *

 * SourcePawn is free software: you can redistribute it and/or modify it under

 * the terms of the GNU General Public License as published by the Free

 * Software Foundation, either version 3 of the License, or (at your option)

 * any later version.

 * 

 * SourcePawn is distributed in the hope that it will be useful, but WITHOUT ANY

 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS

 * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License along with

 * SourcePawn. If not, see http://www.gnu.org/licenses/.

 */

#include <assert.h>

#include "../Zone.h"

#include "../Strings.h"

#include "../NativeTable.h"

#include "../TypeManager.h"

#include "../Modules.h"

#include "../Code.h"

#include "SemanticAnalysis.h"

#include "../Heap-inl.h"

using namespace ke;

#define __ emitter_.

typedef BytecodeEmitter::Label Label;

class AutoEnterScope

{

  public:

    AutoEnterScope(Scope **prevp, Scope *scope)

      : prevp_(prevp),

        prev_(*prevp),

        scope_(scope)

    {

        if (!scope_)

            return;

        prev_ = *prevp_;

        *prevp_ = scope;

        assert(prev_ == scope->enclosing());

    }

    ~AutoEnterScope()

    {

        if (scope_)

            *prevp_ = prev_;

    }

  private:

    Scope **prevp_;

    Scope *prev_;

    Scope *scope_;

};

SemanticAnalysis::SemanticAnalysis(Zone *zone, CompileContext &cc, TranslationUnit *unit)

  : zone_(zone),

    pool_(zone->pool()),

    cc_(cc),

    unit_(unit),

    hir_(NULL),

    emitter_(pool_),

    module_(NULL),

    loop_(NULL)

{

}

SemanticAnalysis::SemanticAnalysis(SemanticAnalysis *parent, Handle<FunctionType> fun)

  : zone_(parent->zone_),

    pool_(parent->pool_),

    cc_(parent->cc_),

    unit_(parent->unit_),

    hir_(NULL),

    scope_(parent->scope_),

    emitter_(pool_),

    module_(parent->module_),

    fun_(fun),

    loop_(NULL),

    control_(NULL)

{

}

void

SemanticAnalysis::analyze()

{

    scope_ = unit_->globalScope();

    module_ = Module::New(zone_);

    for (size_t i = 0; i < unit_->tree()->statements()->length(); i++) {

        Statement *stmt = unit_->tree()->statements()->at(i);

        stmt->accept(this);

    }

    Local<Struct> globals(zone_, unit_->globalScope()->build(zone_));

    if (!globals)

        return;

    module_->setGlobals(globals);

    Local<Code> code(zone_, __ finish());

    if (!code)

        return;

    code->setModule(module_);

    module_->setCode(code);

#ifndef NDEBUG

//    Disassemble(code, stdout);

#endif

    unit_->module_ = module_;

}

void

SemanticAnalysis::visitFunctionStatement(FunctionStatement *stmt)

{

    FunctionSymbol *sym = stmt->sym();

    Local<FunctionType> type(zone_, sym->type());

    assert(scope_->kind() == Scope::GLOBAL);

    if (stmt->token() == TOK_NATIVE) {

        // Define the native now.

        size_t index;

        if (!zone_->nativeTable()->add(stmt->name(), &index))

            return;

        Local<Native> native(zone_, Native::New(zone_, type, index));

        if (!native)

            return;

        __ object(native);

        __ setglobal(sym);

        __ pop();

    }

    // If the function is a forward or native, we don't have to do anything.

    if (stmt->token() == TOK_NATIVE || stmt->token() == TOK_FORWARD)

        return;

    SemanticAnalysis child(this, type);

    Local<Function> funobj(zone_, child.compile(stmt));

    if (!funobj)

        return;

    __ object(funobj);

    __ setglobal(sym);

    if (stmt->token() == TOK_PUBLIC)

        __ public_();

    else

        __ pop();

}

Function *

SemanticAnalysis::compile(FunctionStatement *stmt)

{

    __ setFirstLine(stmt->pos().line);

    AutoEnterScope argScope(&scope_, stmt->argScope());

    for (size_t i = 0; i < stmt->signature().parameters()->length(); i++) {

        Parameter *param = stmt->signature().parameters()->at(i);

        param->sym()->allocate(VariableSymbol::Arg, i);

    }

    AutoEnterScope varScope(&scope_, stmt->varScope());

    ControlStatus status = visitForControl(stmt->body());

    if (!fun_->returnType()->isVoid()) {

        // If the function is not void, report if not all paths return a value.

        // All other incorrect return cases have been caught already.

        if (status.returns() == Returns_Sometimes) {

            cc_.reportError(stmt->pos(), Message_NotAllPathsReturnValue);

            return NULL;

        }

        if (status.returns() == Returns_Never) {

            cc_.reportError(stmt->pos(), Message_MissingReturnValue);

            return NULL;

        }

    }

    Local<Code> code(zone_, __ finish());

    if (!code)

        return NULL;

    code->setModule(module_);

    Local<Function> fun(zone_, Function::New(zone_, code, fun_, stmt->name(), stmt->pos()));

    if (!fun)

        return NULL;

#ifndef NDEBUG

//    Disassemble(code, stdout);

#endif

    return fun;

}

void 

SemanticAnalysis::visitBlockStatement(BlockStatement *node)

{

    AutoEnterScope scope(&scope_, node->scope());

    for (size_t i = 0; i < node->statements()->length(); i++) {

        Statement *stmt = node->statements()->at(i);

        __ note_position(stmt->pos());

        stmt->accept(this);

        assert(__ stackDepth() == 0);

    }

}

void

SemanticAnalysis::visitEnumStatement(EnumStatement *node)

{

}

void

SemanticAnalysis::visitExpressionStatement(ExpressionStatement *node)

{

    // While building HIR, we enter new pool and root scopes, since HIR

    // creation is purely temporary.

    PoolScope poolScope(zone_->pool());

    RootScope rootScope(zone_);

    HIR *hir = eval(node->expression());

    if (!hir)

        return;

    discharge(hir);

    if (!hir->type()->isVoid())

        __ pop();

}

void

SemanticAnalysis::ControlScope::merge(const ControlStatus &left, const ControlStatus &right)

{

    // If both sides terminate in a return, we consider this a return as well.

    if (left.returns() == Returns_Always && right.returns() == Returns_Always) {

        terminate(Returns_Always);

        return;

    }

    ReturnStatus status = (left.returns() == Returns_Never && right.returns() == Returns_Never)

                          ? Returns_Never

                          : Returns_Sometimes;

    if (left.terminates() && right.terminates())

        terminate(status);

    else

        returns(status);

}

SemanticAnalysis::ControlStatus

SemanticAnalysis::visitForControl(Statement *statement)

{

    ControlScope scope(&control_);

    statement->accept(this);

    return scope.status();

}

void

SemanticAnalysis::visitIfStatement(IfStatement *node)

{

    Label join;

    ControlStatus trueBranch;

    ControlStatus falseBranch(false, Returns_Never);

    if (!node->ifFalse()) {

        Label success;

        visitForTest(node->condition(), &success, &join, &success);

        __ bind(&success);

        trueBranch = visitForControl(node->ifTrue());

    } else {

        Label success, next;

        visitForTest(node->condition(), &success, &next, &success);

        __ bind(&success);

        trueBranch = visitForControl(node->ifTrue());

        __ jump(&join);

        __ bind(&next);

        falseBranch = visitForControl(node->ifFalse());

    }

    __ bind(&join);

    control_->merge(trueBranch, falseBranch);

}

void

SemanticAnalysis::requireLifoStack()

{

    if (!loop_)

        return;

    loop_->setUsesLifoStack();

}

SemanticAnalysis::ControlStatus

SemanticAnalysis::visitLoopBody(Statement *stmt)

{

    // We always mark off a loop body, so on each edge, we can balance the

    // LIFO stack. Right now, we don't have the ability to budget the LIFO

    // stack ahead of time. If we turn out to never need the LIFO stack, we

    // mark it as unnecessary. (The interpreter can't really make use of this,

    // but the JIT can).

    //

    // Note that balancing the LIFO stack isn't even necessary, so this

    // feature may be removed. All this mechanism does is mitigate the

    // possibility that a long-running loop will overflow the LIFO region

    // and therefore start requiring nursery allocations.

    int pos = __ enterloop();

    ControlStatus status = visitForControl(stmt);

    __ leaveloop();

    if (loop_->usesLifoStack())

        __ setLoopUsesLifoStack(pos);

    return status;

}

void

SemanticAnalysis::visitForStatement(ForStatement *node)

{

    AutoEnterScope scope(&scope_, node->scope());

    PoolScope poolScope(zone_->pool());

    RootScope rootScope(zone_);

    Label join, update;

    LoopScope loop(scope_, &join, &update, &loop_);

    if (node->initialization())

        node->initialization()->accept(this);

    Label header, test;

    if (node->condition())

        __ jump(&test);

    __ bind(&header);

    ControlStatus status = visitLoopBody(node->body());

    __ bind(&update);

    if (node->update())

        node->update()->accept(this);

    if (node->condition()) {

        __ bind(&test);

        visitForTest(node->condition(), &header, &join, &join);

    } else {

        __ jump(&header);

    }

    __ bind(&join);

    // If there was a condition, we treat this like a while loop. Otherwise,

    // the join point is only reachable if the loop contains a break. The

    // termination status doesn't tell us anything yet.

    if (node->condition() || loop.breaks())

        control_->merge(status, ControlStatus(false, Returns_Never));

    else

        control_->terminate(status.returns());

    assert(__ stackDepth() == 0);

}

void

SemanticAnalysis::visitWhileStatement(WhileStatement *node)

{

    PoolScope poolScope(zone_->pool());

    RootScope rootScope(zone_);

    Label header, join;

    __ bind(&header);

    ControlStatus status;

    LoopScope loop(scope_, &join, &header, &loop_);

    if (node->token() == TOK_WHILE) {

        Label body;

        visitForTest(node->condition(), &body, &join, &body);

        status = visitLoopBody(node->body());

        __ jump(&header);

    } else {

        status = visitLoopBody(node->body());

        visitForTest(node->condition(), &header, &join, &join);

    }

    __ bind(&join);

    // Detect loops that will always have a fork in the contro-flow graph.

    // This will be a |while| loop, or a |do-while| loop whose body does

    // not terminate. For now, we treat these as an |if| regardless of the

    // direction the branch can take. That means the control-flow is always

    // conditional.

    if (node->token() == TOK_WHILE || status.terminates() || loop.breaks()) {

        control_->merge(status, ControlStatus(false, Returns_Never));

    } else {

        // At this point, we've got a do-while loop with a |return| or

        // |continue|, meaning that the rest of the block is unreachable.

        control_->terminate(status.returns());

    }

    assert(__ stackDepth() == 0);

}

static inline Heap::Tenure

InferTenure(Symbol *sym)

{

    if (sym->scope()->kind() == Scope::GLOBAL)

        return Heap::Tenure_Old;

    // SP2's array semantics allow any array kind to escape, so we must use

    // the normal heap. (Hopefully escape analysis can ease this pain later).

    if (sym->type()->isArray())

        return Heap::Tenure_Default;

    return Heap::Tenure_Default;

}

void

SemanticAnalysis::visitVariableDeclaration(VariableDeclaration *node)

{

    PoolScope poolScope(zone_->pool());

    RootScope rootScope(zone_);

    Local<Type> type(zone_, node->sym()->type());

    if (node->sym()->type()->isVoid()) {

        cc_.reportError(node->type()->pos(), Message_CannotDeclareVoid);

        return;

    }

    if (node->initialization()) {

        HIR *hir = NULL;

        if ((hir = eval(node->initialization())) == NULL)

            return;

        if ((hir = coerce(hir, type, Coerce_Decl)) == NULL)

            return;

        discharge(hir);

    } else {

        if (type->isInt32() || type->isEnum() ||

            type->isChar() || type->isBool())

        {

            __ int_(0);

        } else if (type->isFloat()) {

            __ float_(0);

        } else if (type->isArray()) {

            Local<ArrayType> atype(zone_, ArrayType::cast(type));

            Local<ArrayMap> map(zone_, ArrayMap::Attach(zone_, atype));

            if (!map)

                return;

            if (atype->isFixedLength()) {

                __ newarray(OP_NEWFIXED, map, InferTenure(node->sym()));

            } else if (node->dims()->at(0)) {

                // This may not be true if we allow typedefing, so :TODO:

                // figure out proper semantics.

                assert(node->dims()->length() == atype->levels());

                Local<Type> i32(zone_, zone_->types()->getPrimitive(PrimitiveType_Int32));

                for (size_t i = 0; i < node->dims()->length(); i++) {

                    Expression *expr = node->dims()->at(i);

                    if (expr) {

                        HIR *hir = eval(expr);

                        if (!hir || ((hir = coerce(hir, i32, Coerce_Arg)) == NULL))

                            return;

                        discharge(hir);

                    } else {

                        __ int_(0);

                    }

                }

                __ newarray(OP_NEWSIZED, map, InferTenure(node->sym()));

            } else {

                __ newarray(OP_NEWEMPTY, map, InferTenure(node->sym()));

            }

        } else {

            assert(false);

        }

    }

    if (node->sym()->scope()->kind() != Scope::GLOBAL) {

        if (!__ allocate(node->sym()))

            return;

    }

    set(node->sym());

    __ pop();

}

void

SemanticAnalysis::visitReturnStatement(ReturnStatement *node)

{

    control_->returns(Returns_Always);

    if (!node->expression()) {

        if (!fun_->returnType()->isVoid()) {

            cc_.reportError(node->pos(), Message_MissingReturnValue);

            return;

        }

        __ returnvoid();

        return;

    }

    if (fun_->returnType()->isVoid()) {

        cc_.reportError(node->pos(), Message_UsedVoidReturn);

        return;

    }

    PoolScope poolScope(zone_->pool());

    RootScope rootScope(zone_);

    HIR *hir = eval(node->expression());

    if (!hir)

        return;

    Local<Type> returnType(zone_, fun_->returnType());

    if ((hir = coerce(hir, returnType, Coerce_Return)) == NULL)

        return;

    discharge(hir);

    if (hir->type()->isVoid())

        __ returnvoid();

    else

        __ return_();

}

void

SemanticAnalysis::visitBinaryExpression(BinaryExpression *node)

{

    HIR *left = eval(node->left());

    HIR *right = eval(node->right());

    if (!left || !right)

        return;

    hir_ = binary(node, node->token(), left, right);

}

bool

SemanticAnalysis::checkArgumentCount(Handle<FunctionType> type, unsigned actual)

{

    if (type->parameters()->length() == actual)

        return true;

    if (actual > type->parameters()->length()) {

        if (!type->isNative() || !type->isNativeVariadic())

            return false;

        return true;

    }

    if (!type->defaults())

        return false;

    // Missing arguments. See if there's a default argument for each missing

    // actual.

    for (unsigned i = actual; i < type->parameters()->length(); i++) {

        if (!type->defaults()->at(i))

            return false;

    }

    return true;

}