/*
 * Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
 * Use of this file is governed by the BSD 3-clause license that
 * can be found in the LICENSE.txt file in the project root.
 */
package org.antlr.v4.runtime;

import org.antlr.v4.runtime.misc.Interval;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

Useful for rewriting out a buffered input token stream after doing some
augmentation or other manipulations on it.
 You can insert stuff, replace, and delete chunks. Note that the operations are done lazily--only if you convert the buffer to a String with TokenStream.getText(). This is very efficient because you are not moving data around all the time. As the buffer of tokens is converted to strings, the getText() method(s) scan the input token stream and check to see if there is an operation at the current index. If so, the operation is done and then normal String rendering continues on the buffer. This is like having multiple Turing machine instruction streams (programs) operating on a single input tape. :)
 This rewriter makes no modifications to the token stream. It does not ask the stream to fill itself up nor does it advance the input cursor. The token stream IntStream.index() will return the same value before and after any getText() call.
 The rewriter only works on tokens that you have in the buffer and ignores the current input cursor. If you are buffering tokens on-demand, calling getText() halfway through the input will only do rewrites for those tokens in the first half of the file.
 Since the operations are done lazily at getText-time, operations do not screw up the token index values. That is, an insert operation at token index i does not change the index values for tokens i+1..n-1.

Because operations never actually alter the buffer, you may always get the
original token stream back without undoing anything. Since the instructions
are queued up, you can easily simulate transactions and roll back any changes
if there is an error just by removing instructions. For example,
CharStream input = new ANTLRFileStream("input");
TLexer lex = new TLexer(input);
CommonTokenStream tokens = new CommonTokenStream(lex);
T parser = new T(tokens);
TokenStreamRewriter rewriter = new TokenStreamRewriter(tokens);
parser.startRule();


Then in the rules, you can execute (assuming rewriter is visible):
Token t,u;
...
rewriter.insertAfter(t, "text to put after t");}
rewriter.insertAfter(u, "text after u");}
System.out.println(rewriter.getText());


You can also have multiple "instruction streams" and get multiple rewrites
from a single pass over the input. Just name the instruction streams and use
that name again when printing the buffer. This could be useful for generating
a C file and also its header file--all from the same buffer:
rewriter.insertAfter("pass1", t, "text to put after t");}
rewriter.insertAfter("pass2", u, "text after u");}
System.out.println(rewriter.getText("pass1"));
System.out.println(rewriter.getText("pass2"));


If you don't use named rewrite streams, a "default" stream is used as the
first example shows.
/**
 * Useful for rewriting out a buffered input token stream after doing some
 * augmentation or other manipulations on it.
 *
 * <p>
 * You can insert stuff, replace, and delete chunks. Note that the operations
 * are done lazily--only if you convert the buffer to a {@link String} with
 * {@link TokenStream#getText()}. This is very efficient because you are not
 * moving data around all the time. As the buffer of tokens is converted to
 * strings, the {@link #getText()} method(s) scan the input token stream and
 * check to see if there is an operation at the current index. If so, the
 * operation is done and then normal {@link String} rendering continues on the
 * buffer. This is like having multiple Turing machine instruction streams
 * (programs) operating on a single input tape. :)</p>
 *
 * <p>
 * This rewriter makes no modifications to the token stream. It does not ask the
 * stream to fill itself up nor does it advance the input cursor. The token
 * stream {@link TokenStream#index()} will return the same value before and
 * after any {@link #getText()} call.</p>
 *
 * <p>
 * The rewriter only works on tokens that you have in the buffer and ignores the
 * current input cursor. If you are buffering tokens on-demand, calling
 * {@link #getText()} halfway through the input will only do rewrites for those
 * tokens in the first half of the file.</p>
 *
 * <p>
 * Since the operations are done lazily at {@link #getText}-time, operations do
 * not screw up the token index values. That is, an insert operation at token
 * index {@code i} does not change the index values for tokens
 * {@code i}+1..n-1.</p>
 *
 * <p>
 * Because operations never actually alter the buffer, you may always get the
 * original token stream back without undoing anything. Since the instructions
 * are queued up, you can easily simulate transactions and roll back any changes
 * if there is an error just by removing instructions. For example,</p>
 *
 * <pre>
 * CharStream input = new ANTLRFileStream("input");
 * TLexer lex = new TLexer(input);
 * CommonTokenStream tokens = new CommonTokenStream(lex);
 * T parser = new T(tokens);
 * TokenStreamRewriter rewriter = new TokenStreamRewriter(tokens);
 * parser.startRule();
 * </pre>
 *
 * <p>
 * Then in the rules, you can execute (assuming rewriter is visible):</p>
 *
 * <pre>
 * Token t,u;
 * ...
 * rewriter.insertAfter(t, "text to put after t");}
 * rewriter.insertAfter(u, "text after u");}
 * System.out.println(rewriter.getText());
 * </pre>
 *
 * <p>
 * You can also have multiple "instruction streams" and get multiple rewrites
 * from a single pass over the input. Just name the instruction streams and use
 * that name again when printing the buffer. This could be useful for generating
 * a C file and also its header file--all from the same buffer:</p>
 *
 * <pre>
 * rewriter.insertAfter("pass1", t, "text to put after t");}
 * rewriter.insertAfter("pass2", u, "text after u");}
 * System.out.println(rewriter.getText("pass1"));
 * System.out.println(rewriter.getText("pass2"));
 * </pre>
 *
 * <p>
 * If you don't use named rewrite streams, a "default" stream is used as the
 * first example shows.</p>
 */
public class TokenStreamRewriter {
	public static final String DEFAULT_PROGRAM_NAME = "default";
	public static final int PROGRAM_INIT_SIZE = 100;
	public static final int MIN_TOKEN_INDEX = 0;

	// Define the rewrite operation hierarchy

	public class RewriteOperation {
		
What index into rewrites List are we? /** What index into rewrites List are we? */
		protected int instructionIndex;
		
Token buffer index. /** Token buffer index. */
		protected int index;
		protected Object text;

		protected RewriteOperation(int index) {
			this.index = index;
		}

		protected RewriteOperation(int index, Object text) {
			this.index = index;
			this.text = text;
		}
		
Execute the rewrite operation by possibly adding to the buffer.
 Return the index of the next token to operate on.
/** Execute the rewrite operation by possibly adding to the buffer.
		 *  Return the index of the next token to operate on.
		 */
		public int execute(StringBuilder buf) {
			return index;
		}

		@Override
		public String toString() {
			String opName = getClass().getName();
			int $index = opName.indexOf('$');
			opName = opName.substring($index+1, opName.length());
			return "<"+opName+"@"+tokens.get(index)+
					":\""+text+"\">";
		}
	}

	class InsertBeforeOp extends RewriteOperation {
		public InsertBeforeOp(int index, Object text) {
			super(index,text);
		}

		@Override
		public int execute(StringBuilder buf) {
			buf.append(text);
			if ( tokens.get(index).getType()!=Token.EOF ) {
				buf.append(tokens.get(index).getText());
			}
			return index+1;
		}
	}

	
Distinguish between insert after/before to do the "insert afters"
 first and then the "insert befores" at same index. Implementation
 of "insert after" is "insert before index+1".
/** Distinguish between insert after/before to do the "insert afters"
	 *  first and then the "insert befores" at same index. Implementation
	 *  of "insert after" is "insert before index+1".
	 */
    class InsertAfterOp extends InsertBeforeOp {
        public InsertAfterOp(int index, Object text) {
            super(index+1, text); // insert after is insert before index+1
        }
    }

	
I'm going to try replacing range from x..y with (y-x)+1 ReplaceOp
 instructions.
/** I'm going to try replacing range from x..y with (y-x)+1 ReplaceOp
	 *  instructions.
	 */
	class ReplaceOp extends RewriteOperation {
		protected int lastIndex;
		public ReplaceOp(int from, int to, Object text) {
			super(from,text);
			lastIndex = to;
		}
		@Override
		public int execute(StringBuilder buf) {
			if ( text!=null ) {
				buf.append(text);
			}
			return lastIndex+1;
		}
		@Override
		public String toString() {
			if ( text==null ) {
				return "<DeleteOp@"+tokens.get(index)+
						".."+tokens.get(lastIndex)+">";
			}
			return "<ReplaceOp@"+tokens.get(index)+
					".."+tokens.get(lastIndex)+":\""+text+"\">";
		}
	}

	
Our source stream /** Our source stream */
	protected final TokenStream tokens;

	
You may have multiple, named streams of rewrite operations.
 I'm calling these things "programs."
 Maps String (name) → rewrite (List)
/** You may have multiple, named streams of rewrite operations.
	 *  I'm calling these things "programs."
	 *  Maps String (name) &rarr; rewrite (List)
	 */
	protected final Map<String, List<RewriteOperation>> programs;

	
Map String (program name) → Integer index /** Map String (program name) &rarr; Integer index */
	protected final Map<String, Integer> lastRewriteTokenIndexes;

	public TokenStreamRewriter(TokenStream tokens) {
		this.tokens = tokens;
		programs = new HashMap<String, List<RewriteOperation>>();
		programs.put(DEFAULT_PROGRAM_NAME,
					 new ArrayList<RewriteOperation>(PROGRAM_INIT_SIZE));
		lastRewriteTokenIndexes = new HashMap<String, Integer>();
	}

	public final TokenStream getTokenStream() {
		return tokens;
	}

	public void rollback(int instructionIndex) {
		rollback(DEFAULT_PROGRAM_NAME, instructionIndex);
	}

	
Rollback the instruction stream for a program so that
 the indicated instruction (via instructionIndex) is no
 longer in the stream. UNTESTED!
/** Rollback the instruction stream for a program so that
	 *  the indicated instruction (via instructionIndex) is no
	 *  longer in the stream. UNTESTED!
	 */
	public void rollback(String programName, int instructionIndex) {
		List<RewriteOperation> is = programs.get(programName);
		if ( is!=null ) {
			programs.put(programName, is.subList(MIN_TOKEN_INDEX,instructionIndex));
		}
	}

	public void deleteProgram() {
		deleteProgram(DEFAULT_PROGRAM_NAME);
	}

	
Reset the program so that no instructions exist /** Reset the program so that no instructions exist */
	public void deleteProgram(String programName) {
		rollback(programName, MIN_TOKEN_INDEX);
	}

	public void insertAfter(Token t, Object text) {
		insertAfter(DEFAULT_PROGRAM_NAME, t, text);
	}

	public void insertAfter(int index, Object text) {
		insertAfter(DEFAULT_PROGRAM_NAME, index, text);
	}

	public void insertAfter(String programName, Token t, Object text) {
		insertAfter(programName,t.getTokenIndex(), text);
	}

	public void insertAfter(String programName, int index, Object text) {
		// to insert after, just insert before next index (even if past end)
        RewriteOperation op = new InsertAfterOp(index, text);
        List<RewriteOperation> rewrites = getProgram(programName);
        op.instructionIndex = rewrites.size();
        rewrites.add(op);
	}

	public void insertBefore(Token t, Object text) {
		insertBefore(DEFAULT_PROGRAM_NAME, t, text);
	}

	public void insertBefore(int index, Object text) {
		insertBefore(DEFAULT_PROGRAM_NAME, index, text);
	}

	public void insertBefore(String programName, Token t, Object text) {
		insertBefore(programName, t.getTokenIndex(), text);
	}

	public void insertBefore(String programName, int index, Object text) {
		RewriteOperation op = new InsertBeforeOp(index,text);
		List<RewriteOperation> rewrites = getProgram(programName);
		op.instructionIndex = rewrites.size();
		rewrites.add(op);
	}

	public void replace(int index, Object text) {
		replace(DEFAULT_PROGRAM_NAME, index, index, text);
	}

	public void replace(int from, int to, Object text) {
		replace(DEFAULT_PROGRAM_NAME, from, to, text);
	}

	public void replace(Token indexT, Object text) {
		replace(DEFAULT_PROGRAM_NAME, indexT, indexT, text);
	}

	public void replace(Token from, Token to, Object text) {
		replace(DEFAULT_PROGRAM_NAME, from, to, text);
	}

	public void replace(String programName, int from, int to, Object text) {
		if ( from > to || from<0 || to<0 || to >= tokens.size() ) {
			throw new IllegalArgumentException("replace: range invalid: "+from+".."+to+"(size="+tokens.size()+")");
		}
		RewriteOperation op = new ReplaceOp(from, to, text);
		List<RewriteOperation> rewrites = getProgram(programName);
		op.instructionIndex = rewrites.size();
		rewrites.add(op);
	}

	public void replace(String programName, Token from, Token to, Object text) {
		replace(programName,
				from.getTokenIndex(),
				to.getTokenIndex(),
				text);
	}

	public void delete(int index) {
		delete(DEFAULT_PROGRAM_NAME, index, index);
	}

	public void delete(int from, int to) {
		delete(DEFAULT_PROGRAM_NAME, from, to);
	}

	public void delete(Token indexT) {
		delete(DEFAULT_PROGRAM_NAME, indexT, indexT);
	}

	public void delete(Token from, Token to) {
		delete(DEFAULT_PROGRAM_NAME, from, to);
	}

	public void delete(String programName, int from, int to) {
		replace(programName,from,to,null);
	}

	public void delete(String programName, Token from, Token to) {
		replace(programName,from,to,null);
	}

	public int getLastRewriteTokenIndex() {
		return getLastRewriteTokenIndex(DEFAULT_PROGRAM_NAME);
	}

	protected int getLastRewriteTokenIndex(String programName) {
		Integer I = lastRewriteTokenIndexes.get(programName);
		if ( I==null ) {
			return -1;
		}
		return I;
	}

	protected void setLastRewriteTokenIndex(String programName, int i) {
		lastRewriteTokenIndexes.put(programName, i);
	}

	protected List<RewriteOperation> getProgram(String name) {
		List<RewriteOperation> is = programs.get(name);
		if ( is==null ) {
			is = initializeProgram(name);
		}
		return is;
	}

	private List<RewriteOperation> initializeProgram(String name) {
		List<RewriteOperation> is = new ArrayList<RewriteOperation>(PROGRAM_INIT_SIZE);
		programs.put(name, is);
		return is;
	}

	
Return the text from the original tokens altered per the
 instructions given to this rewriter.
/** Return the text from the original tokens altered per the
	 *  instructions given to this rewriter.
 	 */
	public String getText() {
		return getText(DEFAULT_PROGRAM_NAME, Interval.of(0,tokens.size()-1));
	}

	
Return the text from the original tokens altered per the
 instructions given to this rewriter in programName.
/** Return the text from the original tokens altered per the
	 *  instructions given to this rewriter in programName.
 	 */
	public String getText(String programName) {
		return getText(programName, Interval.of(0,tokens.size()-1));
	}

	
Return the text associated with the tokens in the interval from the
 original token stream but with the alterations given to this rewriter.
 The interval refers to the indexes in the original token stream.
 We do not alter the token stream in any way, so the indexes
 and intervals are still consistent. Includes any operations done
 to the first and last token in the interval. So, if you did an
 insertBefore on the first token, you would get that insertion.
 The same is true if you do an insertAfter the stop token.
/** Return the text associated with the tokens in the interval from the
	 *  original token stream but with the alterations given to this rewriter.
	 *  The interval refers to the indexes in the original token stream.
	 *  We do not alter the token stream in any way, so the indexes
	 *  and intervals are still consistent. Includes any operations done
	 *  to the first and last token in the interval. So, if you did an
	 *  insertBefore on the first token, you would get that insertion.
	 *  The same is true if you do an insertAfter the stop token.
 	 */
	public String getText(Interval interval) {
		return getText(DEFAULT_PROGRAM_NAME, interval);
	}

	public String getText(String programName, Interval interval) {
		List<RewriteOperation> rewrites = programs.get(programName);
		int start = interval.a;
		int stop = interval.b;

		// ensure start/end are in range
		if ( stop>tokens.size()-1 ) stop = tokens.size()-1;
		if ( start<0 ) start = 0;

		if ( rewrites==null || rewrites.isEmpty() ) {
			return tokens.getText(interval); // no instructions to execute
		}
		StringBuilder buf = new StringBuilder();

		// First, optimize instruction stream
		Map<Integer, RewriteOperation> indexToOp = reduceToSingleOperationPerIndex(rewrites);

		// Walk buffer, executing instructions and emitting tokens
		int i = start;
		while ( i <= stop && i < tokens.size() ) {
			RewriteOperation op = indexToOp.get(i);
			indexToOp.remove(i); // remove so any left have index size-1
			Token t = tokens.get(i);
			if ( op==null ) {
				// no operation at that index, just dump token
				if ( t.getType()!=Token.EOF ) buf.append(t.getText());
				i++; // move to next token
			}
			else {
				i = op.execute(buf); // execute operation and skip
			}
		}

		// include stuff after end if it's last index in buffer
		// So, if they did an insertAfter(lastValidIndex, "foo"), include
		// foo if end==lastValidIndex.
		if ( stop==tokens.size()-1 ) {
			// Scan any remaining operations after last token
			// should be included (they will be inserts).
			for (RewriteOperation op : indexToOp.values()) {
				if ( op.index >= tokens.size()-1 ) buf.append(op.text);
			}
		}
		return buf.toString();
	}

	
We need to combine operations and report invalid operations (like
 overlapping replaces that are not completed nested). Inserts to
 same index need to be combined etc...  Here are the cases:
 I.i.u I.j.v								leave alone, nonoverlapping
 I.i.u I.i.v								combine: Iivu
 R.i-j.u R.x-y.v	| i-j in x-y			delete first R
 R.i-j.u R.i-j.v							delete first R
 R.i-j.u R.x-y.v	| x-y in i-j			ERROR
 R.i-j.u R.x-y.v	| boundaries overlap	ERROR
 Delete special case of replace (text==null):
 D.i-j.u D.x-y.v	| boundaries overlap	combine to max(min)..max(right)
 I.i.u R.x-y.v | i in (x+1)-y			delete I (since insert before
										we're not deleting i)
 I.i.u R.x-y.v | i not in (x+1)-y		leave alone, nonoverlapping
 R.x-y.v I.i.u | i in x-y				ERROR
 R.x-y.v I.x.u 							R.x-y.uv (combine, delete I)
 R.x-y.v I.i.u | i not in x-y			leave alone, nonoverlapping
 I.i.u = insert u before op @ index i
 R.x-y.u = replace x-y indexed tokens with u
 First we need to examine replaces. For any replace op:
		1. wipe out any insertions before op within that range.
	2. Drop any replace op before that is contained completely within
 that range.
	3. Throw exception upon boundary overlap with any previous replace.
 Then we can deal with inserts:
		1. for any inserts to same index, combine even if not adjacent.
		2. for any prior replace with same left boundary, combine this
 insert with replace and delete this replace.
		3. throw exception if index in same range as previous replace
 Don't actually delete; make op null in list. Easier to walk list.
 Later we can throw as we add to index → op map.
 Note that I.2 R.2-2 will wipe out I.2 even though, technically, the
 inserted stuff would be before the replace range. But, if you
 add tokens in front of a method body '{' and then delete the method
 body, I think the stuff before the '{' you added should disappear too.
 Return a map from token index to operation.
/** We need to combine operations and report invalid operations (like
	 *  overlapping replaces that are not completed nested). Inserts to
	 *  same index need to be combined etc...  Here are the cases:
	 *
	 *  I.i.u I.j.v								leave alone, nonoverlapping
	 *  I.i.u I.i.v								combine: Iivu
	 *
	 *  R.i-j.u R.x-y.v	| i-j in x-y			delete first R
	 *  R.i-j.u R.i-j.v							delete first R
	 *  R.i-j.u R.x-y.v	| x-y in i-j			ERROR
	 *  R.i-j.u R.x-y.v	| boundaries overlap	ERROR
	 *
	 *  Delete special case of replace (text==null):
	 *  D.i-j.u D.x-y.v	| boundaries overlap	combine to max(min)..max(right)
	 *
	 *  I.i.u R.x-y.v | i in (x+1)-y			delete I (since insert before
	 *											we're not deleting i)
	 *  I.i.u R.x-y.v | i not in (x+1)-y		leave alone, nonoverlapping
	 *  R.x-y.v I.i.u | i in x-y				ERROR
	 *  R.x-y.v I.x.u 							R.x-y.uv (combine, delete I)
	 *  R.x-y.v I.i.u | i not in x-y			leave alone, nonoverlapping
	 *
	 *  I.i.u = insert u before op @ index i
	 *  R.x-y.u = replace x-y indexed tokens with u
	 *
	 *  First we need to examine replaces. For any replace op:
	 *
	 * 		1. wipe out any insertions before op within that range.
	 *		2. Drop any replace op before that is contained completely within
	 *	 that range.
	 *		3. Throw exception upon boundary overlap with any previous replace.
	 *
	 *  Then we can deal with inserts:
	 *
	 * 		1. for any inserts to same index, combine even if not adjacent.
	 * 		2. for any prior replace with same left boundary, combine this
	 *	 insert with replace and delete this replace.
	 * 		3. throw exception if index in same range as previous replace
	 *
	 *  Don't actually delete; make op null in list. Easier to walk list.
	 *  Later we can throw as we add to index &rarr; op map.
	 *
	 *  Note that I.2 R.2-2 will wipe out I.2 even though, technically, the
	 *  inserted stuff would be before the replace range. But, if you
	 *  add tokens in front of a method body '{' and then delete the method
	 *  body, I think the stuff before the '{' you added should disappear too.
	 *
	 *  Return a map from token index to operation.
	 */
	protected Map<Integer, RewriteOperation> reduceToSingleOperationPerIndex(List<RewriteOperation> rewrites) {
//		System.out.println("rewrites="+rewrites);

		// WALK REPLACES
		for (int i = 0; i < rewrites.size(); i++) {
			RewriteOperation op = rewrites.get(i);
			if ( op==null ) continue;
			if ( !(op instanceof ReplaceOp) ) continue;
			ReplaceOp rop = (ReplaceOp)rewrites.get(i);
			// Wipe prior inserts within range
			List<? extends InsertBeforeOp> inserts = getKindOfOps(rewrites, InsertBeforeOp.class, i);
			for (InsertBeforeOp iop : inserts) {
				if ( iop.index == rop.index ) {
					// E.g., insert before 2, delete 2..2; update replace
					// text to include insert before, kill insert
					rewrites.set(iop.instructionIndex, null);
					rop.text = iop.text.toString() + (rop.text!=null?rop.text.toString():"");
				}
				else if ( iop.index > rop.index && iop.index <= rop.lastIndex ) {
					// delete insert as it's a no-op.
					rewrites.set(iop.instructionIndex, null);
				}
			}
			// Drop any prior replaces contained within
			List<? extends ReplaceOp> prevReplaces = getKindOfOps(rewrites, ReplaceOp.class, i);
			for (ReplaceOp prevRop : prevReplaces) {
				if ( prevRop.index>=rop.index && prevRop.lastIndex <= rop.lastIndex ) {
					// delete replace as it's a no-op.
					rewrites.set(prevRop.instructionIndex, null);
					continue;
				}
				// throw exception unless disjoint or identical
				boolean disjoint =
					prevRop.lastIndex<rop.index || prevRop.index > rop.lastIndex;
				// Delete special case of replace (text==null):
				// D.i-j.u D.x-y.v	| boundaries overlap	combine to max(min)..max(right)
				if ( prevRop.text==null && rop.text==null && !disjoint ) {
					//System.out.println("overlapping deletes: "+prevRop+", "+rop);
					rewrites.set(prevRop.instructionIndex, null); // kill first delete
					rop.index = Math.min(prevRop.index, rop.index);
					rop.lastIndex = Math.max(prevRop.lastIndex, rop.lastIndex);
					System.out.println("new rop "+rop);
				}
				else if ( !disjoint ) {
					throw new IllegalArgumentException("replace op boundaries of "+rop+" overlap with previous "+prevRop);
				}
			}
		}

		// WALK INSERTS
		for (int i = 0; i < rewrites.size(); i++) {
			RewriteOperation op = rewrites.get(i);
			if ( op==null ) continue;
			if ( !(op instanceof InsertBeforeOp) ) continue;
			InsertBeforeOp iop = (InsertBeforeOp)rewrites.get(i);
			// combine current insert with prior if any at same index
			List<? extends InsertBeforeOp> prevInserts = getKindOfOps(rewrites, InsertBeforeOp.class, i);
			for (InsertBeforeOp prevIop : prevInserts) {
				if ( prevIop.index==iop.index ) {
					if ( InsertAfterOp.class.isInstance(prevIop) ) {
						iop.text = catOpText(prevIop.text, iop.text);
						rewrites.set(prevIop.instructionIndex, null);
					}
					else if ( InsertBeforeOp.class.isInstance(prevIop) ) { // combine objects
						// convert to strings...we're in process of toString'ing
						// whole token buffer so no lazy eval issue with any templates
						iop.text = catOpText(iop.text, prevIop.text);
						// delete redundant prior insert
						rewrites.set(prevIop.instructionIndex, null);
					}
				}
			}
			// look for replaces where iop.index is in range; error
			List<? extends ReplaceOp> prevReplaces = getKindOfOps(rewrites, ReplaceOp.class, i);
			for (ReplaceOp rop : prevReplaces) {
				if ( iop.index == rop.index ) {
					rop.text = catOpText(iop.text,rop.text);
					rewrites.set(i, null);	// delete current insert
					continue;
				}
				if ( iop.index >= rop.index && iop.index <= rop.lastIndex ) {
					throw new IllegalArgumentException("insert op "+iop+" within boundaries of previous "+rop);
				}
			}
		}
		// System.out.println("rewrites after="+rewrites);
		Map<Integer, RewriteOperation> m = new HashMap<Integer, RewriteOperation>();
		for (int i = 0; i < rewrites.size(); i++) {
			RewriteOperation op = rewrites.get(i);
			if ( op==null ) continue; // ignore deleted ops
			if ( m.get(op.index)!=null ) {
				throw new Error("should only be one op per index");
			}
			m.put(op.index, op);
		}
		//System.out.println("index to op: "+m);
		return m;
	}

	protected String catOpText(Object a, Object b) {
		String x = "";
		String y = "";
		if ( a!=null ) x = a.toString();
		if ( b!=null ) y = b.toString();
		return x+y;
	}

	
Get all operations before an index of a particular kind /** Get all operations before an index of a particular kind */
	protected <T extends RewriteOperation> List<? extends T> getKindOfOps(List<? extends RewriteOperation> rewrites, Class<T> kind, int before) {
		List<T> ops = new ArrayList<T>();
		for (int i=0; i<before && i<rewrites.size(); i++) {
			RewriteOperation op = rewrites.get(i);
			if ( op==null ) continue; // ignore deleted
			if ( kind.isInstance(op) ) {
				ops.add(kind.cast(op));
			}
		}
		return ops;
	}
}