package com.github.liblevenshtein.transducer;
/**
* Transitions a transposition, Levenshtein position to all possible positions,
* given a set of parameters.
* @author Dylon Edwards
* @since 2.1.0
*/
public class TranspositionPositionTransitionFunction extends PositionTransitionFunction {
private static final long serialVersionUID = 1L;
/**
* {@inheritDoc}
*/
@Override
@SuppressWarnings("checkstyle:methodlength")
public State of(
final int n,
final Position position,
final boolean[] characteristicVector,
final int offset) {
final int i = position.termIndex();
final int e = position.numErrors();
final boolean t = position.isSpecial();
final int h = i - offset;
final int w = characteristicVector.length;
if (e == 0 && 0 < n) {
if (h <= w - 2) {
final int a = n - e < Integer.MAX_VALUE
? n - e + 1
: Integer.MAX_VALUE;
final int b = w - h;
final int k = a < b ? a : b;
final int j = indexOf(characteristicVector, k, h);
switch (j) {
case 0:
return stateFactory.build(
// [No Error]: Increment the index by one; leave the error and
// special state alone
positionFactory.build(i + 1, 0, false)
);
case 1:
return stateFactory.build(
// [Insertion]: Leave index alone; increment the error by one.
positionFactory.build(i, 1, false),
// [Transposition]: Leave index alone; increment error by one.
positionFactory.build(i, 1, true),
// [Substitution]: Replace the current character; increment the
// index by one; increment the error by one.
positionFactory.build(i + 1, 1, false),
// [Deletion]: Increment the index by one-more than a single
// deletion; increment the error by one.
positionFactory.build(i + 2, 1, false)
);
case -1:
return stateFactory.build(
// [Insertion]: Leave index alone; increment the error by one.
positionFactory.build(i, 1, false),
// [Substitution]: Replace the current character; increment the
// index by one; increment the error by one.
positionFactory.build(i + 1, 1, false)
);
default: // j > 1
return stateFactory.build(
// [Insertion]: Leave index alone; increment the error by one.
positionFactory.build(i, 1, false),
// [Substitution]: Replace the current character; increment the
// index by one; increment the error by one.
positionFactory.build(i + 1, 1, false),
// [Deletion]: Increment index by one-more than the number of
// deletions; increment error by the number of deletions.
positionFactory.build(i + j + 1, j, false)
);
}
}
if (h == w - 1) {
if (characteristicVector[h]) {
return stateFactory.build(
// [No Error]: Increment index by one; leave error alone
positionFactory.build(i + 1, 0, false)
);
}
return stateFactory.build(
// [Insertion]: Leave index alone; increment error by one.
positionFactory.build(i, 1, false),
// [Substitution]: Increment index by one; increment error by one.
positionFactory.build(i + 1, 1, false)
);
}
// else, h == 2
return stateFactory.build(
// [Insertion]: Leave index alone; increment error by one.
positionFactory.build(i, 1, false)
);
}
if (1 <= e && e < n) {
if (h <= w - 2) {
if (!t) {
final int a = n - e < Integer.MAX_VALUE
? n - e + 1
: Integer.MAX_VALUE;
final int b = w - h;
final int k = a < b ? a : b;
final int j = indexOf(characteristicVector, k, h);
switch (j) {
case 0:
return stateFactory.build(
// [No Error]: Increment index by one; leave error alone.
positionFactory.build(i + 1, e, false)
);
case 1:
return stateFactory.build(
// [Insertion]: Leave index alone; increment error by one.
positionFactory.build(i, e + 1, false),
// [Transposition]: Leave index alone; increment error by one.
positionFactory.build(i, e + 1, true),
// [Substitution]: Increment index by one; increment error by
// one.
positionFactory.build(i + 1, e + 1, false),
// [Deletion]: Increment index by one-more than one deletion;
// increment error by one.
positionFactory.build(i + 2, e + 1, false)
);
case -1:
return stateFactory.build(
// [Insertion]: Leave index alone; increment error by one.
positionFactory.build(i, e + 1, false),
// [Substitution]: Increment index by one; increment error by
// one.
positionFactory.build(i + 1, e + 1, false)
);
default: // j > 1
return stateFactory.build(
// [Insertion]: Leave index alone; increment error by one.
positionFactory.build(i, e + 1, false),
// [Substitution]: Increment index by one; increment error by
// one.
positionFactory.build(i + 1, e + 1, false),
// [Deletion]: Increment index by one-more than number of
// deletions; increment error by number of deletions.
positionFactory.build(i + j + 1, e + j, false)
);
}
}
if (characteristicVector[h]) {
return stateFactory.build(
// [No Error]: Increment index by two; leave error alone.
positionFactory.build(i + 2, e, false)
);
}
// [Too Many Errors]: The edit distance has exceeded the max distance
// for the candidate term.
return null;
}
if (h == w - 1) {
if (characteristicVector[h]) {
return stateFactory.build(
// [No Error]: Increment index by one; leave error alone.
positionFactory.build(i + 1, e, false)
);
}
return stateFactory.build(
// [Insertion]: Leave index alone; increment error by one.
positionFactory.build(i, e + 1, false),
// [Substitution]: Increment index by one; leave error alone.
positionFactory.build(i + 1, e + 1, false)
);
}
// else, h == w
return stateFactory.build(
// [Insertion]: Leave index alone; increment error by one.
positionFactory.build(i, e + 1, false)
);
}
if (h <= w - 1 && !t) {
if (characteristicVector[h]) {
return stateFactory.build(
// [No Error]: Increment index by one; leave error alone.
positionFactory.build(i + 1, n, false)
);
}
// [Too Many Errors]: The edit distance has exceeded the max distance for
// the candidate term.
return null;
}
if (h <= w - 2 && t) {
if (characteristicVector[h]) {
return stateFactory.build(
// [No Error]: Increment index by two; leave error alone.
positionFactory.build(i + 2, n, false)
);
}
// [Too Many Errors]: The edit distance has exceeded the max distance for
// the candidate term.
return null;
}
// else, h == w
// ------------
// [Too Many Errors]: The edit distance has exceeded the max distance for
// the candidate term.
return null;
}
}