/*
 * Copyright 2017 - 2019 Volker Berlin (i-net software)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package de.inetsoftware.jwebassembly.text;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;

import de.inetsoftware.jwebassembly.JWebAssembly;
import de.inetsoftware.jwebassembly.WasmException;
import de.inetsoftware.jwebassembly.module.FunctionName;
import de.inetsoftware.jwebassembly.module.ModuleWriter;
import de.inetsoftware.jwebassembly.module.TypeManager.StructType;
import de.inetsoftware.jwebassembly.module.ValueTypeConvertion;
import de.inetsoftware.jwebassembly.module.WasmTarget;
import de.inetsoftware.jwebassembly.wasm.AnyType;
import de.inetsoftware.jwebassembly.wasm.ArrayOperator;
import de.inetsoftware.jwebassembly.wasm.NamedStorageType;
import de.inetsoftware.jwebassembly.wasm.NumericOperator;
import de.inetsoftware.jwebassembly.wasm.StructOperator;
import de.inetsoftware.jwebassembly.wasm.ValueType;
import de.inetsoftware.jwebassembly.wasm.VariableOperator;
import de.inetsoftware.jwebassembly.wasm.WasmBlockOperator;

/**
 * Module Writer for text format with S-expressions.
 * 
 * @author Volker Berlin
 *
 */
public class TextModuleWriter extends ModuleWriter {

    private final boolean               spiderMonkey     = Boolean.getBoolean( "SpiderMonkey" );

    private Appendable                  output;

    private final boolean               debugNames;

    private final ByteArrayOutputStream dataStream       = new ByteArrayOutputStream();

    private final ArrayList<String>     methodParamNames = new ArrayList<>();

    private StringBuilder               typeOutput       = new StringBuilder();

    private ArrayList<String>           types            = new ArrayList<>();

    private StringBuilder               methodOutput;

    private StringBuilder               imports          = new StringBuilder();

    private Map<String, Function>       functions        = new LinkedHashMap<>();

    private final Set<String>           functionNames    = new HashSet<>();

    private int                         inset;

    private boolean                     isImport;

    private boolean                     isPrepared;

    private HashSet<String>             globals          = new HashSet<>();

    private boolean                     useExceptions;

    private boolean                     callIndirect;

    /**
     * Create a new instance.
     * 
     * @param target
     *            target for the result
     * @param properties
     *            compiler properties
     * @throws IOException
     *             if any I/O error occur
     */
    public TextModuleWriter( WasmTarget target, HashMap<String, String> properties ) throws IOException {
        this.output = target.getTextOutput();
        debugNames = Boolean.parseBoolean( properties.get( JWebAssembly.DEBUG_NAMES ) );
        output.append( "(module" );
        inset++;
        if( spiderMonkey ) {
            output.append( " (gc_feature_opt_in 3)" ); // enable GcFeatureOptIn for SpiderMonkey https://github.com/lars-t-hansen/moz-gc-experiments/blob/master/version2.md
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void close() throws IOException {
        for( int i = 0; i < types.size(); i++ ) {
            newline( output );
            output.append( "(type $t" ).append( Integer.toString( i ) ).append( " (func" ).append( types.get( i ) ).append( "))" );
        }

        output.append( imports );

        for( Function func : functions.values() ) {
            output.append( func.output );
        }

        if( callIndirect ) {
            int count = functions.size();
            String countStr = Integer.toString( count );
            newline( output );
            output.append( "(table " ).append( countStr ).append( ' ' ).append( countStr ).append( " anyfunc)" );
            newline( output );
            output.append( "(elem (i32.const 0) " );
            for( int i = 0; i < count; i++ ) {
                output.append( Integer.toString( i ) ).append( ' ' );
            }
            output.append( ')' );
        }

        int dataSize = dataStream.size();
        if( dataSize > 0 ) {
            int pages = (dataSize + 0xFFFF) / 0x10000;
            newline( output );
            String pagesStr = Integer.toString( pages );
            output.append( "(memory " ).append( pagesStr ).append( ' ' ).append( pagesStr ).append( ')' );
            newline( output );
            output.append( "(data (i32.const 0) \"" );
            byte[] data = dataStream.toByteArray();
            for( byte b : data ) {
                output.append( '\\' ).append( Character.forDigit( (b >> 4) & 0xF, 16 ) ).append( Character.forDigit( b & 0xF, 16 ) );
            }
            output.append( "\")" );
        }

        inset--;
        newline( output );
        output.append( ')' );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected int writeStructType( StructType type ) throws IOException {
        type.setVTable( dataStream.size() );
        for( FunctionName funcName : type.getMethods() ) {
            int functIdx = getFunction( funcName ).id;
            // little-endian byte order
            dataStream.write( functIdx >>> 0 );
            dataStream.write( functIdx >>> 8 );
            dataStream.write( functIdx >>> 16 );
            dataStream.write( functIdx >>> 24 );
        }

        int oldInset = inset;
        inset = 1;
        newline( output );
        String typeName = normalizeName( type.getName() );
        output.append( "(type $" ).append( typeName ).append( " (struct" );
        inset++;
        for( NamedStorageType field : type.getFields() ) {
            newline( output );
            output.append( "(field" );
            if( debugNames && field.getName() != null ) {
                output.append( " $" ).append( typeName ).append(  '.' ).append( field.getName() );
            }
            output.append( " (mut " );
            writeTypeName( output, field.getType() );
            output.append( "))" );
        }
        inset--;
        newline( output );
        output.append( "))" );
        inset = oldInset;
        return 0;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void writeException() throws IOException {
        if( !useExceptions ) {
            useExceptions = true;
            int oldInset = inset;
            inset = 1;
            newline( output );
            output.append( "(event (param anyref))" );
            inset = oldInset;
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void prepareFinish() {
        isPrepared = true;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void prepareImport( FunctionName name, String importModule, String importName ) throws IOException {
        if( importName != null ) {
            methodOutput = imports;
            newline( methodOutput );
            methodOutput.append( "(import \"" ).append( importModule ).append( "\" \"" ).append( importName ).append( "\" (func $" ).append( normalizeName( name ) );
            isImport = true;
        }
    }

    /**
     * Normalize the function name for the text format
     * 
     * @param name
     *            the name
     * @return the normalized name
     */
    @Nonnull
    private String normalizeName( FunctionName name ) {
        Function function = getFunction( name );
        if( function.name == null ) {
            String base;
            String str = base = normalizeName( name.fullName );
            for( int i = 1; functionNames.contains( str ); i++ ) {
                str = base + '.' + i;
            }
            functionNames.add( str );
            function.name = str;
        }
        return function.name;
    }

    /**
     * Normalize the function name for the text format
     * 
     * @param name
     *            the name
     * @return the normalized name
     */
    @Nonnull
    private String normalizeName( String name ) {
        if( spiderMonkey ) {
            name = name.replace( '/', '.' ).replace( '<', '_' ).replace( '>', '_' ); // TODO HACK for https://bugzilla.mozilla.org/show_bug.cgi?id=1511485
        }
        return name;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void writeExport( FunctionName name, String exportName ) throws IOException {
        newline( output );
        output.append( "(export \"" ).append( exportName ).append( "\" (func $" ).append( normalizeName( name ) ).append( "))" );
    }

    /**
     * Write the name of a type.
     * 
     * @param output
     *            the target
     * @param type
     *            the type
     * @throws IOException
     *             if any I/O error occur
     */
    private void writeTypeName( Appendable output, AnyType type ) throws IOException {
        if( type.getCode() < 0 ) {
            output.append( type.toString() );
        } else {
            output.append( "(ref " ).append( normalizeName( type.toString() ) ).append( ')' );
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void writeMethodParamStart( @Nonnull FunctionName name ) throws IOException {
        typeOutput.setLength( 0 );
        methodParamNames.clear();
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void writeMethodParam( String kind, AnyType valueType, @Nullable String name ) throws IOException {
        if( kind != "local" ) {
            typeOutput.append( '(' ).append( kind ).append( ' ' );
            writeTypeName( typeOutput, valueType );
            typeOutput.append( ')' );
        }
        if( methodOutput == null ) {
            return;
        }
        methodOutput.append( '(' ).append( kind );
        if( debugNames ) { 
            if( name != null ) {
                methodOutput.append( " $" ).append( name );
            }
            if( kind != "result" ) {
                methodParamNames.add( name );
            }
        }
        methodOutput.append( ' ' );
        writeTypeName( methodOutput, valueType );
        methodOutput.append( ')' );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void writeMethodParamFinish( @Nonnull FunctionName name ) throws IOException {
        String typeStr = typeOutput.toString();
        int idx = types.indexOf( typeStr );
        if( idx < 0 ) {
            idx = types.size();
            types.add( typeStr );
        }
        getFunction( name ).typeId = idx;

        if( isImport ) {
            isImport = false;
            methodOutput.append( "))" );
            methodOutput = null;
        }
    }

    private Function getFunction( FunctionName name ) {
        Function func = functions.get( name.signatureName );
        if( func == null ) {
            func = new Function();
            func.id = functions.size();
            functions.put( name.signatureName, func );
        }
        return func;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void writeMethodStart( FunctionName name, String sourceFile ) throws IOException {
        methodOutput = getFunction( name ).output;

        newline( methodOutput );
        methodOutput.append( "(func $" );
        methodOutput.append( normalizeName( name ) );
        inset++;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void markSourceLine( int javaSourceLine ) {
        // nothing
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void writeMethodFinish() throws IOException {
        inset--;
        newline( methodOutput );
        methodOutput.append( ')' );
        methodOutput = null;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void writeConst( Number value, ValueType valueType ) throws IOException {
        newline( methodOutput );
        methodOutput.append( valueType ).append( ".const " );
        switch( valueType ) {
            case f32:
                methodOutput.append( Float.toHexString( value.floatValue() ).toLowerCase() ).append( " ;;" ).append( value );
                break;
            case f64:
                methodOutput.append( Double.toHexString( value.doubleValue() ).toLowerCase() ).append( " ;;" ).append( value );
                break;
            default:
                methodOutput.append( value );
                break;
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void writeLocal( VariableOperator op, int idx ) throws IOException {
        newline( methodOutput );
        methodOutput.append( "local." ).append( op ).append( ' ' );
        String name = idx < methodParamNames.size() ? methodParamNames.get( idx ) : null;
        if( name == null ) {
            methodOutput.append( Integer.toString( idx ) );
        } else {
            methodOutput.append( '$' ).append( name );
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void writeGlobalAccess( boolean load, FunctionName name, AnyType type ) throws IOException {
        String fullName = normalizeName( name.fullName );
        if( !globals.contains( fullName ) ) {
            // declare global variable if not already declared.
            output.append( "\n  " );
            output.append( "(global $" ).append( fullName ).append( " (mut " );
            writeTypeName( output, type );
            output.append( ')' );
            writeDefaultValue( output, type );
            output.append( ')' );
            globals.add( fullName );
        }
        newline( methodOutput );
        methodOutput.append( load ? "global.get $" : "global.set $" ).append( fullName );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void writeDefaultValue( AnyType type ) throws IOException {
        newline( methodOutput );
        writeDefaultValue( methodOutput, type );
    }

    /**
     * Write the default/initial value for type.
     * 
     * @param output
     *            the target
     * @param type
     *            the type
     * @throws IOException
     *             if an I/O error occurs.
     */
    private static void writeDefaultValue( Appendable output, AnyType type ) throws IOException {
        if( type.getCode() < 0 ) {
            ValueType valueType = (ValueType)type;
            switch( valueType ) {
                case i32:
                case i64:
                case f32:
                case f64:
                    output.append( type.toString() ).append( ".const 0" );
                    break;
                case i8:
                case i16:
                    writeDefaultValue( output, ValueType.i32 );
                    break;
                case anyref:
                    output.append( "ref.null" );
                    break;
                default:
                    throw new WasmException( "Not supported storage type: " + type, -1 );
            }
        } else {
            output.append( "ref.null" );
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void writeNumericOperator( NumericOperator numOp, @Nullable ValueType valueType ) throws IOException {
        newline( methodOutput );
        String op = numOp.toString();
        switch( valueType ) {
            case i32:
            case i64:
                switch( numOp ) {
                    case div:
                    case rem:
                    case gt:
                    case lt:
                    case le:
                    case ge:
                        op += "_s";
                        break;
                    case ifnonnull:
                        methodOutput.append( "ref.is_null" );
                        writeNumericOperator( NumericOperator.eqz, ValueType.i32 );
                        return;
                    case ifnull:
                        methodOutput.append( "ref.is_null" );
                        return;
                    case ref_ne:
                        methodOutput.append( "ref.eq" );
                        writeNumericOperator( NumericOperator.eqz, ValueType.i32 );
                        return;
                    case ref_eq:
                        methodOutput.append( "ref.eq" );
                        return;
                    default:
                }
                break;
            default:
        }
        methodOutput.append( valueType ).append( '.' ).append( op );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void writeCast( ValueTypeConvertion cast ) throws IOException {
        String op;
        switch( cast ) {
            case i2l:
                op = "i64.extend_i32_s";
                break;
            case i2f:
                op = "f32.convert_i32_s";
                break;
            case i2d:
                op = "f64.convert_i32_s";
                break;
            case l2i:
                op = "i32.wrap_i64";
                break;
            case l2f:
                op = "f32.convert_i64_s";
                break;
            case l2d:
                op = "f64.convert_i64_s";
                break;
            case f2i:
                op = "i32.trunc_sat_f32_s";
                break;
            case f2l:
                op = "i64.trunc_sat_f32_s";
                break;
            case f2d:
                op = "f64.promote_f32";
                break;
            case d2i:
                op = "i32.trunc_sat_f64_s";
                break;
            case d2l:
                op = "i64.trunc_sat_f64_s";
                break;
            case d2f:
                op = "f32.demote_f64";
                break;
            case i2b:
                op = "i32.extend8_s";
                break;
            case i2s:
                op = "i32.extend16_s";
                break;
            case f2i_re:
                op = "i32.reinterpret_f32";
                break;
            case i2f_re:
                op = "f32.reinterpret_i32";
                break;
            case d2l_re:
                op = "i64.reinterpret_f64";
                break;
            case l2d_re:
                op = "f64.reinterpret_i64";
                break;
            default:
                throw new Error( "Unknown cast/type conversion: " + cast );
        }
        newline( methodOutput );
        methodOutput.append( op );
    }

    /**
     * Add a newline with the insets.
     * 
     * @param output
     *            the target
     * @throws IOException
     *             if any I/O error occur
     */
    private void newline( Appendable output ) throws IOException {
        output.append( '\n' );
        for( int i = 0; i < inset; i++ ) {
            output.append( ' ' );
            output.append( ' ' );
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void writeFunctionCall( FunctionName name ) throws IOException {
        newline( methodOutput );
        methodOutput.append( "call $" ).append( normalizeName( name ) );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void writeVirtualFunctionCall( FunctionName name, AnyType type, int virtualFunctionIdx, int tempVarIdx ) throws IOException {
        callIndirect = true;

        // duplicate this on the stack
        writeLocal( VariableOperator.tee, tempVarIdx );
        writeLocal( VariableOperator.get, tempVarIdx );

        newline( methodOutput );
        methodOutput.append( "struct.get " ).append( normalizeName( type.toString() ) ).append( " 0 ;;vtable" ); // vtable is ever on position 0
        newline( methodOutput );
        methodOutput.append( "i32.load offset=" ).append( virtualFunctionIdx * 4 ); // use default alignment
        newline( methodOutput );
        if(spiderMonkey)
            methodOutput.append( "call_indirect $t" ).append( functions.get( name.signatureName ).typeId ); // https://bugzilla.mozilla.org/show_bug.cgi?id=1556779
        else
        methodOutput.append( "call_indirect (type $t" ).append( functions.get( name.signatureName ).typeId ).append( ')' );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void writeBlockCode( @Nonnull WasmBlockOperator op, @Nullable Object data ) throws IOException {
        String name;
        int insetAfter = 0;
        switch( op ) {
            case RETURN:
                name = "return";
                break;
            case IF:
                name = "if";
                if( data != ValueType.empty ) {
                    name += " (result " + data + ")";
                }
                insetAfter++;
                break;
            case ELSE:
                inset--;
                name = "else";
                insetAfter++;
                break;
            case END:
                inset--;
                name = "end";
                break;
            case DROP:
                name = "drop";
                break;
            case BLOCK:
                name = "block";
                if( data != null ) {
                    name += " (result " + data + ")";
                }
                insetAfter++;
                break;
            case BR:
                name = "br " + data;
                break;
            case BR_IF:
                name = "br_if " + data;
                break;
            case BR_TABLE:
                StringBuilder builder = new StringBuilder( "br_table");
                for( int i : (int[])data ) {
                    builder.append( ' ' ).append( i );
                }
                name = builder.toString();
                break;
            case LOOP:
                name = "loop";
                insetAfter++;
                break;
            case UNREACHABLE:
                name = "unreachable";
                break;
            case TRY:
                name = "try";
                insetAfter++;
                break;
            case CATCH:
                inset--;
                name = "catch";
                insetAfter++;
                break;
            case THROW:
                name = "throw 0"; // currently there is only one event/exception with anyref
                break;
            case RETHROW:
                name = "rethrow";
                break;
            case BR_ON_EXN:
                name = "br_on_exn " + data + " 0"; // br_on_exn, break depth, event; // currently there is only one event/exception with anyref
                break;
            case MONITOR_ENTER:
            case MONITOR_EXIT:
                name = "drop";
                break;
            default:
                throw new Error( "Unknown block: " + op );
        }
        newline( methodOutput );
        methodOutput.append( name );
        inset += insetAfter;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void writeArrayOperator( @Nonnull ArrayOperator op, AnyType type ) throws IOException {
        String operation;
        switch( op ) {
            case NEW:
                operation = "new";
                break;
            case GET:
                operation = "get";
                break;
            case SET:
                operation = "set";
                break;
            case LENGTH:
                operation = "len";
                break;
            default:
                throw new Error( "Unknown operator: " + op );
        }
        newline( methodOutput );
        methodOutput.append( "array." ).append( operation ).append( ' ' ).append( type );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void writeStructOperator( StructOperator op, AnyType type, NamedStorageType fieldName, int idx ) throws IOException {
        String operation;
        switch( op ) {
            case NEW:
            case NEW_DEFAULT:
                operation = "struct.new";
                break;
            case GET:
                operation = "struct.get";
                break;
            case SET:
                operation = "struct.set";
                break;
            case NULL:
                operation = "ref.null";
                type = null;
                break;
            default:
                throw new Error( "Unknown operator: " + op );
        }
        newline( methodOutput );
        methodOutput.append( operation );
        if( type != null ) {
            methodOutput.append( ' ' ).append( normalizeName( type.toString() ) );
        }
        if( fieldName != null ) {
            methodOutput.append(  ' ' ).append( idx ).append( " ;; $" ).append( normalizeName( fieldName.getName() ) );
        }
    }
}