/*
 * Anarres C Preprocessor
 * Copyright (c) 2007-2015, Shevek
 *
 * 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 org.anarres.cpp;

import java.io.Closeable;
import java.io.IOException;
import java.util.Iterator;
import javax.annotation.CheckForNull;
import javax.annotation.Nonnegative;
import javax.annotation.Nonnull;
import static org.anarres.cpp.Token.CCOMMENT;
import static org.anarres.cpp.Token.CPPCOMMENT;
import static org.anarres.cpp.Token.EOF;
import static org.anarres.cpp.Token.NL;
import static org.anarres.cpp.Token.WHITESPACE;

/**
 * An input to the Preprocessor.
 *
 * Inputs may come from Files, Strings or other sources. The
 * preprocessor maintains a stack of Sources. Operations such as
 * file inclusion or token pasting will push a new source onto
 * the Preprocessor stack. Sources pop from the stack when they
 * are exhausted; this may be transparent or explicit.
 *
 * BUG: Error messages are not handled properly.
 */
public abstract class Source implements Iterable<Token>, Closeable {

    private Source parent;
    private boolean autopop;
    private PreprocessorListener listener;
    private boolean active;
    private boolean werror;

    /* LineNumberReader */

    /*
     // We can't do this, since we would lose the LexerException
     private class Itr implements Iterator {
     private Token      next = null;
     private void advance() {
     try {
     if (next != null)
     next = token();
     }
     catch (IOException e) {
     throw new UnsupportedOperationException(
     "Failed to advance token iterator: " +
     e.getMessage()
     );
     }
     }
     public boolean hasNext() {
     return next.getType() != EOF;
     }
     public Token next() {
     advance();
     Token      t = next;
     next = null;
     return t;
     }
     public void remove() {
     throw new UnsupportedOperationException(
     "Cannot remove tokens from a Source."
     );
     }
     }
     */
    public Source() {
        this.parent = null;
        this.autopop = false;
        this.listener = null;
        this.active = true;
        this.werror = false;
    }

    /**
     * Sets the parent source of this source.
     *
     * Sources form a singly linked list.
     */
    /* pp */ void setParent(Source parent, boolean autopop) {
        this.parent = parent;
        this.autopop = autopop;
    }

    /**
     * Returns the parent source of this source.
     *
     * Sources form a singly linked list.
     */
    /* pp */ final Source getParent() {
        return parent;
    }


    // @OverrideMustInvoke
        /* pp */ void init(Preprocessor pp) {
        setListener(pp.getListener());
        this.werror = pp.getWarnings().contains(Warning.ERROR);
    }

    /**
     * Sets the listener for this Source.
     *
     * Normally this is set by the Preprocessor when a Source is
     * used, but if you are using a Source as a standalone object,
     * you may wish to call this.
     */
    public void setListener(PreprocessorListener pl) {
        this.listener = pl;
    }

    /**
     * Returns the File currently being lexed.
     *
     * If this Source is not a {@link FileLexerSource}, then
     * it will ask the parent Source, and so forth recursively.
     * If no Source on the stack is a FileLexerSource, returns null.
     */
    @CheckForNull
    public String getPath() {
        Source parent = getParent();
        if (parent != null)
            return parent.getPath();
        return null;
    }

    /**
     * Returns the human-readable name of the current Source.
     */
    @CheckForNull
    public String getName() {
        Source parent = getParent();
        if (parent != null)
            return parent.getName();
        return null;
    }

    /**
     * Returns the current line number within this Source.
     */
    @Nonnegative
    public int getLine() {
        Source parent = getParent();
        if (parent == null)
            return 0;
        return parent.getLine();
    }

    /**
     * Returns the current column number within this Source.
     */
    public int getColumn() {
        Source parent = getParent();
        if (parent == null)
            return 0;
        return parent.getColumn();
    }

    /**
     * Returns true if this Source is expanding the given macro.
     *
     * This is used to prevent macro recursion.
     */
    /* pp */ boolean isExpanding(@Nonnull Macro m) {
        Source parent = getParent();
        if (parent != null)
            return parent.isExpanding(m);
        return false;
    }

    /**
     * Returns true if this Source should be transparently popped
     * from the input stack.
     *
     * Examples of such sources are macro expansions.
     */
    /* pp */ boolean isAutopop() {
        return autopop;
    }

    /**
     * Returns true if this source has line numbers.
     */
    /* pp */ boolean isNumbered() {
        return false;
    }

    /* This is an incredibly lazy way of disabling warnings when
     * the source is not active. */
    /* pp */ void setActive(boolean b) {
        this.active = b;
    }

    /* pp */ boolean isActive() {
        return active;
    }

    /**
     * Returns the next Token parsed from this input stream.
     *
     * @see Token
     */
    @Nonnull
    public abstract Token token()
            throws IOException,
            LexerException;

    /**
     * Returns a token iterator for this Source.
     */
    @Override
    public Iterator<Token> iterator() {
        return new SourceIterator(this);
    }

    /**
     * Skips tokens until the end of line.
     *
     * @param white true if only whitespace is permitted on the
     *  remainder of the line.
     * @return the NL token.
     */
    @Nonnull
    public Token skipline(boolean white)
            throws IOException,
            LexerException {
        for (;;) {
            Token tok = token();
            switch (tok.getType()) {
                case EOF:
                    /* There ought to be a newline before EOF.
                     * At least, in any skipline context. */
                    /* XXX Are we sure about this? */
                    warning(tok.getLine(), tok.getColumn(),
                            "No newline before end of file");
                    return new Token(NL,
                            tok.getLine(), tok.getColumn(),
                            "\n");
                // return tok;
                case NL:
                    /* This may contain one or more newlines. */
                    return tok;
                case CCOMMENT:
                case CPPCOMMENT:
                case WHITESPACE:
                    break;
                default:
                    /* XXX Check white, if required. */
                    if (white)
                        warning(tok.getLine(), tok.getColumn(),
                                "Unexpected nonwhite token");
                    break;
            }
        }
    }

    protected void error(int line, int column, String msg)
            throws LexerException {
        if (listener != null)
            listener.handleError(this, line, column, msg);
        else
            throw new LexerException("Error at " + line + ":" + column + ": " + msg);
    }

    protected void warning(int line, int column, String msg)
            throws LexerException {
        if (werror)
            error(line, column, msg);
        else if (listener != null)
            listener.handleWarning(this, line, column, msg);
        else
            throw new LexerException("Warning at " + line + ":" + column + ": " + msg);
    }

    public void close()
            throws IOException {
    }

}