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package org.jruby.ir.persistence;

import org.jcodings.Encoding;
import org.jruby.RubySymbol;
import org.jruby.ir.IRScope;
import org.jruby.ir.IRScopeType;
import org.jruby.ir.Operation;
import org.jruby.ir.instructions.Instr;
import org.jruby.ir.operands.Operand;
import org.jruby.ir.operands.OperandType;
import org.jruby.parser.StaticScope;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

import org.jruby.runtime.RubyEvent;
import org.jruby.runtime.Signature;
import org.jruby.util.ByteList;

import static com.headius.backport9.buffer.Buffers.flipBuffer;

// FIXME: Make into a base class at some point to play with different formats

/**
 * Represents a file which is persisted to storage.
 */
public class IRWriterStream implements IRWriterEncoder, IRPersistenceValues {
    private final Map<IRScope, Integer> scopeInstructionOffsets = new HashMap<>();
    private final Map<IRScope, Integer> scopePoolOffsets = new HashMap<>();
    // FIXME: Allocate direct and use one per thread?
    private final ByteBuffer buf = ByteBuffer.allocate(TWO_MEGS);
    private final OutputStream stream;
    private final IRWriterAnalyzer analyzer;
    private Map<RubySymbol, Integer> constantMap = new HashMap();

    int headersOffset = -1;

    public IRWriterStream(OutputStream stream) {
        this.stream = stream;
        this.analyzer = new IRWriterAnalyzer();
    }

    public IRWriterStream(File file) throws FileNotFoundException {
        this(new FileOutputStream(file));
    }

    /**
     * Record current offset as the beginning of specified scopes list of instructions.
     */
    public void addScopeInstructionOffset(IRScope scope) {
        scopeInstructionOffsets.put(scope, offset());
    }

    private int offset() {
        return buf.position() + PROLOGUE_LENGTH;
    }

    /**
     * Get recorded offset for this scropes instruction list.
     */
    public int getScopeInstructionOffset(IRScope scope) {
        return scopeInstructionOffsets.get(scope);
    }

    @Override
    public void encode(boolean value) {
        buf.put((byte) (value ? TRUE : FALSE));
    }

    @Override
    public void encode(byte value) {
        buf.put(value);
    }

    @Override
    public void encode(char value) {
        buf.putChar(value);
    }

    @Override
    public void encode(int value) {
        //FIXME: Use bit math
        // We can write 7 bits of ints as a single byte and if 8th is set we end
        // using first byte to indicate full precision int.
        if (value >= 0 && value <= 127) {
            buf.put((byte) value);
        } else {
            buf.put(FULL);
            buf.putInt(value);
        }
    }

    @Override
    public void encode(int[] value) {
        encode(value.length);
        for (int i = 0; i < value.length; i++) {
            encode(value[i]);
        }
    }

    @Override
    public void encode(long value) {
        if (value >= 0 && value <= 127) {
            encode((byte) value);
        } else {
            buf.put(FULL);
            buf.putLong(value);
        }
    }

    @Override
    public void encode(float value) {
//        buf.put(FLOAT);
        buf.putFloat(value);
    }

    @Override
    public void encode(double value) {
//        buf.put(DOUBLE);
        buf.putDouble(value);
    }

    @Override
    public void encode(ByteList value) {
        encode(value.bytes());
        encode(value.getEncoding());
    }

    @Override
    public void encode(byte[] bytes) {
        encode(bytes.length);
        buf.put(bytes);
    }

    @Override
    public void encode(Encoding encoding) {
        encode(encoding.getName());
    }

    @Override
    public void encode(RubySymbol symbol) {
        Integer constantIndex = constantMap.get(symbol);

        if (constantIndex != null) {
            encode(constantIndex.intValue());
        } else {
            int index = constantMap.size();
            constantMap.put(symbol, index);
            encode(index);
        }
    }

    public void encodeRaw(RubySymbol symbol) {
        if (symbol == null) {
            encode(NULL_STRING);
        } else {
            encode(symbol.getBytes());
        }
    }

    @Override
    public void encode(String value) {
        if (value == null) {
            encode(NULL_STRING);
        } else {
            byte[] bytes = value.getBytes();
            encode(bytes.length);
            buf.put(bytes);
        }
    }

    // This cannot tell difference between null and [] which is ok.  Possibly we should even allow
    // encoding null.
    @Override
    public void encode(String[] values) {
        if (values == null) {
            encode((int) 0);
            return;
        }

        encode(values.length);
        for (String value : values) {
            encode(value.length());
            buf.put(value.getBytes());
        }
    }

    @Override
    public void encode(Operand operand) {
        operand.encode(this);
    }

    @Override
    public void encode(Operand[] operands) {
        encode(operands.length);
        for(Operand arg: operands) {
            encode(arg);
        }
    }

    @Override
    public void encode(Instr instr) {
        instr.encode(this);
    }

    @Override
    public void encode(IRScope value) {
        encode(analyzer.getScopeID(value));
    }

    @Override
    public void encode(IRScopeType value) {
        encode((byte) value.ordinal());
    }

    @Override
    public void encode(Signature signature) {
        // Non-method/block scopes still have this field so we set it to no-arg by convention.
        if (signature == null) signature = Signature.NO_ARGUMENTS;
        encode(signature.encode());
    }

    @Override
    public void encode(RubyEvent event) {
        encode((byte) event.ordinal());
    }

    @Override
    public void encode(StaticScope.Type value) {
        encode((byte) value.ordinal());
    }

    @Override
    public void encode(Operation value) {
        encode(value.ordinal());
    }

    @Override
    public void encode(OperandType value) {
        encode((byte) value.ordinal());
    }

    @Override
    public void startEncodingScopeHeader(IRScope scope) {
    }

    @Override
    public void endEncodingScopeHeader(IRScope scope) {
        encode(getScopeInstructionOffset(scope)); // Write out offset to where this scopes instrs are
        encode(scopePoolOffsets.get(scope));
    }

    @Override
    public void startEncodingScopeInstrs(IRScope scope) {
        constantMap.clear();
        addScopeInstructionOffset(scope); // Record offset so we add this value to scope headers entry
        encode(scope.getInterpreterContext().getInstructions().length); // Allows us to right-size when reconstructing instr list.
    }

    @Override
    public void endEncodingScopeInstrs(IRScope scope) {
        scopePoolOffsets.put(scope, offset());

        List<Entry<RubySymbol, Integer> > list = new LinkedList(constantMap.entrySet());
        Collections.sort(list, Comparator.comparing(Entry::getValue));

        encode(list.size());    // How many entries are within pool
        for (Entry<RubySymbol, Integer> entry: list) {
            encodeRaw(entry.getKey());
        }
    }

    @Override
    public void startEncodingScopeHeaders(IRScope script) {
        headersOffset = offset();
        encode(analyzer.getScopeCount());
    }

    @Override
    public void endEncodingScopeHeaders(IRScope script) {
    }

    @Override
    public void startEncoding(IRScope script) {
        try {
            IRWriter.persist(analyzer, script);
        } catch (IOException ex) {
            // No IO so no exception possible for analyzer.
        }
    }

    @Override
    public void endEncoding(IRScope script) {
        try {
            stream.write(ByteBuffer.allocate(4).putInt(VERSION).array());
            stream.write(ByteBuffer.allocate(4).putInt(headersOffset).array());
            flipBuffer(buf);
            stream.write(buf.array(), buf.position(), buf.limit());
            stream.close();
        } catch (IOException e) {
            try { if (stream != null) stream.close(); } catch (IOException e1) {}
        }
    }
}
