/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the "Elastic License
 * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
 * Public License v 1"; you may not use this file except in compliance with, at
 * your election, the "Elastic License 2.0", the "GNU Affero General Public
 * License v3.0 only", or the "Server Side Public License, v 1".
 */

package org.elasticsearch.painless.phase;

import org.elasticsearch.core.Strings;
import org.elasticsearch.painless.AnalyzerCaster;
import org.elasticsearch.painless.Location;
import org.elasticsearch.painless.ScriptClassInfo;
import org.elasticsearch.painless.lookup.PainlessCast;
import org.elasticsearch.painless.lookup.PainlessLookupUtility;
import org.elasticsearch.painless.lookup.PainlessMethod;
import org.elasticsearch.painless.lookup.def;
import org.elasticsearch.painless.node.AExpression;
import org.elasticsearch.painless.node.AStatement;
import org.elasticsearch.painless.node.ECallLocal;
import org.elasticsearch.painless.node.SBlock;
import org.elasticsearch.painless.node.SExpression;
import org.elasticsearch.painless.node.SFunction;
import org.elasticsearch.painless.node.SReturn;
import org.elasticsearch.painless.symbol.Decorations;
import org.elasticsearch.painless.symbol.Decorations.AllEscape;
import org.elasticsearch.painless.symbol.Decorations.ExpressionPainlessCast;
import org.elasticsearch.painless.symbol.Decorations.Internal;
import org.elasticsearch.painless.symbol.Decorations.LastSource;
import org.elasticsearch.painless.symbol.Decorations.LoopEscape;
import org.elasticsearch.painless.symbol.Decorations.MethodEscape;
import org.elasticsearch.painless.symbol.Decorations.Read;
import org.elasticsearch.painless.symbol.Decorations.TargetType;
import org.elasticsearch.painless.symbol.Decorations.ThisPainlessMethod;
import org.elasticsearch.painless.symbol.Decorations.ValueType;
import org.elasticsearch.painless.symbol.FunctionTable.LocalFunction;
import org.elasticsearch.painless.symbol.ScriptScope;
import org.elasticsearch.painless.symbol.SemanticScope;
import org.elasticsearch.painless.symbol.SemanticScope.FunctionScope;

import java.util.List;

import static org.elasticsearch.painless.symbol.SemanticScope.newFunctionScope;

public class PainlessSemanticAnalysisPhase extends DefaultSemanticAnalysisPhase {

    /** Current function while in {@code visitFunction} */
    protected String functionName = "";

    @Override
    public void visitFunction(SFunction userFunctionNode, ScriptScope scriptScope) {
        functionName = userFunctionNode.getFunctionName();

        if ("execute".equals(functionName)) {
            ScriptClassInfo scriptClassInfo = scriptScope.getScriptClassInfo();
            LocalFunction localFunction = scriptScope.getFunctionTable()
                .getFunction(functionName, scriptClassInfo.getExecuteArguments().size());
            List<Class<?>> typeParameters = localFunction.getTypeParameters();
            FunctionScope functionScope = newFunctionScope(scriptScope, localFunction.getReturnType());

            for (int i = 0; i < typeParameters.size(); ++i) {
                Class<?> typeParameter = localFunction.getTypeParameters().get(i);
                String parameterName = scriptClassInfo.getExecuteArguments().get(i).name();
                functionScope.defineVariable(userFunctionNode.getLocation(), typeParameter, parameterName, false);
            }

            for (int i = 0; i < scriptClassInfo.getGetMethods().size(); ++i) {
                Class<?> typeParameter = scriptClassInfo.getGetReturns().get(i);
                org.objectweb.asm.commons.Method method = scriptClassInfo.getGetMethods().get(i);
                String parameterName = method.getName().substring(3);
                parameterName = Character.toLowerCase(parameterName.charAt(0)) + parameterName.substring(1);
                functionScope.defineVariable(userFunctionNode.getLocation(), typeParameter, parameterName, false);
            }

            SBlock userBlockNode = userFunctionNode.getBlockNode();

            if (userBlockNode.getStatementNodes().isEmpty()) {
                throw userFunctionNode.createError(
                    new IllegalArgumentException(
                        Strings.format(
                            "invalid function definition: found no statements for function [%s] with [%d] parameters",
                            functionName,
                            typeParameters.size()
                        )
                    )
                );
            }

            functionScope.setCondition(userBlockNode, LastSource.class);
            visit(userBlockNode, functionScope.newLocalScope());
            boolean methodEscape = functionScope.getCondition(userBlockNode, MethodEscape.class);

            if (methodEscape) {
                functionScope.setCondition(userFunctionNode, MethodEscape.class);
            }

            scriptScope.setUsedVariables(functionScope.getUsedVariables());
        } else {
            super.visitFunction(userFunctionNode, scriptScope);
        }

        functionName = "";
    }

    /**
     * Visits an expression that is also considered a statement.
     *
     * If the statement is a return from the execute method, performs return value conversion.
     *
     * Checks: control flow, type validation
     */
    @Override
    public void visitExpression(SExpression userExpressionNode, SemanticScope semanticScope) {
        Class<?> rtnType = semanticScope.getReturnType();
        boolean isVoid = rtnType == void.class;
        boolean lastSource = semanticScope.getCondition(userExpressionNode, LastSource.class);
        AExpression userStatementNode = userExpressionNode.getStatementNode();

        if (lastSource && isVoid == false) {
            semanticScope.setCondition(userStatementNode, Read.class);
        }

        checkedVisit(userStatementNode, semanticScope);
        Class<?> expressionValueType = semanticScope.getDecoration(userStatementNode, Decorations.ValueType.class).valueType();
        boolean rtn = lastSource && isVoid == false && expressionValueType != void.class;

        if (rtn) {
            semanticScope.putDecoration(userStatementNode, new TargetType(rtnType));
            semanticScope.setCondition(userStatementNode, Internal.class);
            if ("execute".equals(functionName)) {
                decorateWithCastForReturn(
                    userStatementNode,
                    userExpressionNode,
                    semanticScope,
                    semanticScope.getScriptScope().getScriptClassInfo()
                );
            } else {
                decorateWithCast(userStatementNode, semanticScope);
            }

            semanticScope.setCondition(userExpressionNode, MethodEscape.class);
            semanticScope.setCondition(userExpressionNode, LoopEscape.class);
            semanticScope.setCondition(userExpressionNode, AllEscape.class);
        }
    }

    /**
     * Visits a return statement and casts the value to the return type if possible.
     *
     * If the statement is a return from the execute method, performs return value conversion.
     *
     * Checks: type validation
     */
    @Override
    public void visitReturn(SReturn userReturnNode, SemanticScope semanticScope) {
        AExpression userValueNode = userReturnNode.getValueNode();

        if (userValueNode == null) {
            if (semanticScope.getReturnType() != void.class) {
                throw userReturnNode.createError(
                    new ClassCastException(
                        Strings.format(
                            "cannot cast from [%s] to [%s]",
                            semanticScope.getReturnCanonicalTypeName(),
                            PainlessLookupUtility.typeToCanonicalTypeName(void.class)
                        )
                    )
                );
            }
        } else {
            semanticScope.setCondition(userValueNode, Read.class);
            semanticScope.putDecoration(userValueNode, new TargetType(semanticScope.getReturnType()));
            semanticScope.setCondition(userValueNode, Internal.class);
            checkedVisit(userValueNode, semanticScope);
            if ("execute".equals(functionName)) {
                decorateWithCastForReturn(
                    userValueNode,
                    userReturnNode,
                    semanticScope,
                    semanticScope.getScriptScope().getScriptClassInfo()
                );
            } else {
                decorateWithCast(userValueNode, semanticScope);
            }
        }

        semanticScope.setCondition(userReturnNode, MethodEscape.class);
        semanticScope.setCondition(userReturnNode, LoopEscape.class);
        semanticScope.setCondition(userReturnNode, AllEscape.class);
    }

    /**
     * Decorates a user expression node with a PainlessCast.
     */
    public static void decorateWithCastForReturn(
        AExpression userExpressionNode,
        AStatement parent,
        SemanticScope semanticScope,
        ScriptClassInfo scriptClassInfo
    ) {
        Location location = userExpressionNode.getLocation();
        Class<?> valueType = semanticScope.getDecoration(userExpressionNode, Decorations.ValueType.class).valueType();
        Class<?> targetType = semanticScope.getDecoration(userExpressionNode, TargetType.class).targetType();

        PainlessCast painlessCast;
        if (valueType == def.class) {
            if (scriptClassInfo.defConverter != null) {
                semanticScope.putDecoration(parent, new Decorations.Converter(scriptClassInfo.defConverter));
                return;
            }
        } else {
            for (LocalFunction converter : scriptClassInfo.converters) {
                try {
                    painlessCast = AnalyzerCaster.getLegalCast(location, valueType, converter.getTypeParameters().get(0), false, true);
                    if (painlessCast != null) {
                        semanticScope.putDecoration(userExpressionNode, new ExpressionPainlessCast(painlessCast));
                    }
                    semanticScope.putDecoration(parent, new Decorations.Converter(converter));
                    return;
                } catch (ClassCastException e) {
                    // Do nothing, we're checking all converters
                }
            }
        }

        boolean isExplicitCast = semanticScope.getCondition(userExpressionNode, Decorations.Explicit.class);
        boolean isInternalCast = semanticScope.getCondition(userExpressionNode, Internal.class);
        painlessCast = AnalyzerCaster.getLegalCast(location, valueType, targetType, isExplicitCast, isInternalCast);
        if (painlessCast != null) {
            semanticScope.putDecoration(userExpressionNode, new ExpressionPainlessCast(painlessCast));
        }
    }

    @Override
    public void visitCallLocal(ECallLocal userCallLocalNode, SemanticScope semanticScope) {
        if ("$".equals(userCallLocalNode.getMethodName())) {
            ScriptScope scriptScope = semanticScope.getScriptScope();
            PainlessMethod thisMethod = scriptScope.getPainlessLookup()
                .lookupPainlessMethod(scriptScope.getScriptClassInfo().getBaseClass(), false, "field", 1);

            if (thisMethod == null) {
                throw new IllegalArgumentException("invalid shortcut [$] for [field]; ensure [field] exists in this context");
            }

            semanticScope.setUsesInstanceMethod();
            semanticScope.putDecoration(userCallLocalNode, new ThisPainlessMethod(thisMethod));

            // we specify the parameters here as String for the field name, and def for the default value
            // we don't know the type of field at compile-time or the method since we use duck-typing
            // so the default value has to be def
            Class<?>[] typeParameters = new Class<?>[] { String.class, def.class };
            List<AExpression> userArgumentNodes = userCallLocalNode.getArgumentNodes();
            int userArgumentsSize = userArgumentNodes.size();

            if (userArgumentsSize != 2) {
                throw new IllegalArgumentException(
                    "invalid number of arguments for [$] shortcut for [field]; expected <field name> and <default value>"
                );
            }

            for (int argument = 0; argument < userArgumentsSize; ++argument) {
                AExpression userArgumentNode = userArgumentNodes.get(argument);

                semanticScope.setCondition(userArgumentNode, Read.class);
                semanticScope.putDecoration(userArgumentNode, new TargetType(typeParameters[argument]));
                semanticScope.setCondition(userArgumentNode, Internal.class);
                checkedVisit(userArgumentNode, semanticScope);
                decorateWithCast(userArgumentNode, semanticScope);
            }

            semanticScope.putDecoration(userCallLocalNode, new ValueType(def.class));
        } else {
            super.visitCallLocal(userCallLocalNode, semanticScope);
        }
    }
}