// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html#License
/*
 *******************************************************************************
 * Copyright (C) 1996-2015, International Business Machines
 * Corporation and others.  All Rights Reserved.
 *******************************************************************************
 * CollationCompare.java, ported from collationcompare.h/.cpp
 *
 * C++ version created on: 2012feb14 with new and old collation code
 * created by: Markus W. Scherer
 */

package com.ibm.icu.impl.coll;

import com.ibm.icu.text.Collator;

public final class CollationCompare /* all static */ {
    public static int compareUpToQuaternary(CollationIterator left, CollationIterator right,
            CollationSettings settings) {
        int options = settings.options;
        long variableTop;
        if ((options & CollationSettings.ALTERNATE_MASK) == 0) {
            variableTop = 0;
        } else {
            // +1 so that we can use "<" and primary ignorables test out early.
            variableTop = settings.variableTop + 1;
        }
        boolean anyVariable = false;

        // Fetch CEs, compare primaries, store secondary & tertiary weights.
        for (;;) {
            // We fetch CEs until we get a non-ignorable primary or reach the end.
            long leftPrimary;
            do {
                long ce = left.nextCE();
                leftPrimary = ce >>> 32;
                if (leftPrimary < variableTop && leftPrimary > Collation.MERGE_SEPARATOR_PRIMARY) {
                    // Variable CE, shift it to quaternary level.
                    // Ignore all following primary ignorables, and shift further variable CEs.
                    anyVariable = true;
                    do {
                        // Store only the primary of the variable CE.
                        left.setCurrentCE(ce & 0xffffffff00000000L);
                        for (;;) {
                            ce = left.nextCE();
                            leftPrimary = ce >>> 32;
                            if (leftPrimary == 0) {
                                left.setCurrentCE(0);
                            } else {
                                break;
                            }
                        }
                    } while (leftPrimary < variableTop && leftPrimary > Collation.MERGE_SEPARATOR_PRIMARY);
                }
            } while (leftPrimary == 0);

            long rightPrimary;
            do {
                long ce = right.nextCE();
                rightPrimary = ce >>> 32;
                if (rightPrimary < variableTop && rightPrimary > Collation.MERGE_SEPARATOR_PRIMARY) {
                    // Variable CE, shift it to quaternary level.
                    // Ignore all following primary ignorables, and shift further variable CEs.
                    anyVariable = true;
                    do {
                        // Store only the primary of the variable CE.
                        right.setCurrentCE(ce & 0xffffffff00000000L);
                        for (;;) {
                            ce = right.nextCE();
                            rightPrimary = ce >>> 32;
                            if (rightPrimary == 0) {
                                right.setCurrentCE(0);
                            } else {
                                break;
                            }
                        }
                    } while (rightPrimary < variableTop && rightPrimary > Collation.MERGE_SEPARATOR_PRIMARY);
                }
            } while (rightPrimary == 0);

            if (leftPrimary != rightPrimary) {
                // Return the primary difference, with script reordering.
                if (settings.hasReordering()) {
                    leftPrimary = settings.reorder(leftPrimary);
                    rightPrimary = settings.reorder(rightPrimary);
                }
                return (leftPrimary < rightPrimary) ? Collation.LESS : Collation.GREATER;
            }
            if (leftPrimary == Collation.NO_CE_PRIMARY) {
                break;
            }
        }

        // Compare the buffered secondary & tertiary weights.
        // We might skip the secondary level but continue with the case level
        // which is turned on separately.
        if (CollationSettings.getStrength(options) >= Collator.SECONDARY) {
            if ((options & CollationSettings.BACKWARD_SECONDARY) == 0) {
                int leftIndex = 0;
                int rightIndex = 0;
                for (;;) {
                    int leftSecondary;
                    do {
                        leftSecondary = ((int) left.getCE(leftIndex++)) >>> 16;
                    } while (leftSecondary == 0);

                    int rightSecondary;
                    do {
                        rightSecondary = ((int) right.getCE(rightIndex++)) >>> 16;
                    } while (rightSecondary == 0);

                    if (leftSecondary != rightSecondary) {
                        return (leftSecondary < rightSecondary) ? Collation.LESS : Collation.GREATER;
                    }
                    if (leftSecondary == Collation.NO_CE_WEIGHT16) {
                        break;
                    }
                }
            } else {
                // The backwards secondary level compares secondary weights backwards
                // within segments separated by the merge separator (U+FFFE, weight 02).
                int leftStart = 0;
                int rightStart = 0;
                for (;;) {
                    // Find the merge separator or the NO_CE terminator.
                    long p;
                    int leftLimit = leftStart;
                    while ((p = left.getCE(leftLimit) >>> 32) > Collation.MERGE_SEPARATOR_PRIMARY
                            || p == 0) {
                        ++leftLimit;
                    }
                    int rightLimit = rightStart;
                    while ((p = right.getCE(rightLimit) >>> 32) > Collation.MERGE_SEPARATOR_PRIMARY
                            || p == 0) {
                        ++rightLimit;
                    }

                    // Compare the segments.
                    int leftIndex = leftLimit;
                    int rightIndex = rightLimit;
                    for (;;) {
                        int leftSecondary = 0;
                        while (leftSecondary == 0 && leftIndex > leftStart) {
                            leftSecondary = ((int) left.getCE(--leftIndex)) >>> 16;
                        }

                        int rightSecondary = 0;
                        while (rightSecondary == 0 && rightIndex > rightStart) {
                            rightSecondary = ((int) right.getCE(--rightIndex)) >>> 16;
                        }

                        if (leftSecondary != rightSecondary) {
                            return (leftSecondary < rightSecondary) ? Collation.LESS : Collation.GREATER;
                        }
                        if (leftSecondary == 0) {
                            break;
                        }
                    }

                    // Did we reach the end of either string?
                    // Both strings have the same number of merge separators,
                    // or else there would have been a primary-level difference.
                    assert (left.getCE(leftLimit) == right.getCE(rightLimit));
                    if (p == Collation.NO_CE_PRIMARY) {
                        break;
                    }
                    // Skip both merge separators and continue.
                    leftStart = leftLimit + 1;
                    rightStart = rightLimit + 1;
                }
            }
        }

        if ((options & CollationSettings.CASE_LEVEL) != 0) {
            int strength = CollationSettings.getStrength(options);
            int leftIndex = 0;
            int rightIndex = 0;
            for (;;) {
                int leftCase, leftLower32, rightCase;
                if (strength == Collator.PRIMARY) {
                    // Primary+caseLevel: Ignore case level weights of primary ignorables.
                    // Otherwise we would get a-umlaut > a
                    // which is not desirable for accent-insensitive sorting.
                    // Check for (lower 32 bits) == 0 as well because variable CEs are stored
                    // with only primary weights.
                    long ce;
                    do {
                        ce = left.getCE(leftIndex++);
                        leftCase = (int) ce;
                    } while ((ce >>> 32) == 0 || leftCase == 0);
                    leftLower32 = leftCase;
                    leftCase &= 0xc000;

                    do {
                        ce = right.getCE(rightIndex++);
                        rightCase = (int) ce;
                    } while ((ce >>> 32) == 0 || rightCase == 0);
                    rightCase &= 0xc000;
                } else {
                    // Secondary+caseLevel: By analogy with the above,
                    // ignore case level weights of secondary ignorables.
                    //
                    // Note: A tertiary CE has uppercase case bits (0.0.ut)
                    // to keep tertiary+caseFirst well-formed.
                    //
                    // Tertiary+caseLevel: Also ignore case level weights of secondary ignorables.
                    // Otherwise a tertiary CE's uppercase would be no greater than
                    // a primary/secondary CE's uppercase.
                    // (See UCA well-formedness condition 2.)
                    // We could construct a special case weight higher than uppercase,
                    // but it's simpler to always ignore case weights of secondary ignorables,
                    // turning 0.0.ut into 0.0.0.t.
                    // (See LDML Collation, Case Parameters.)
                    do {
                        leftCase = (int) left.getCE(leftIndex++);
                    } while ((leftCase & 0xffff0000) == 0);
                    leftLower32 = leftCase;
                    leftCase &= 0xc000;

                    do {
                        rightCase = (int) right.getCE(rightIndex++);
                    } while ((rightCase & 0xffff0000) == 0);
                    rightCase &= 0xc000;
                }

                // No need to handle NO_CE and MERGE_SEPARATOR specially:
                // There is one case weight for each previous-level weight,
                // so level length differences were handled there.
                if (leftCase != rightCase) {
                    if ((options & CollationSettings.UPPER_FIRST) == 0) {
                        return (leftCase < rightCase) ? Collation.LESS : Collation.GREATER;
                    } else {
                        return (leftCase < rightCase) ? Collation.GREATER : Collation.LESS;
                    }
                }
                if ((leftLower32 >>> 16) == Collation.NO_CE_WEIGHT16) {
                    break;
                }
            }
        }
        if (CollationSettings.getStrength(options) <= Collator.SECONDARY) {
            return Collation.EQUAL;
        }

        int tertiaryMask = CollationSettings.getTertiaryMask(options);

        int leftIndex = 0;
        int rightIndex = 0;
        int anyQuaternaries = 0;
        for (;;) {
            int leftLower32, leftTertiary;
            do {
                leftLower32 = (int) left.getCE(leftIndex++);
                anyQuaternaries |= leftLower32;
                assert ((leftLower32 & Collation.ONLY_TERTIARY_MASK) != 0 || (leftLower32 & 0xc0c0) == 0);
                leftTertiary = leftLower32 & tertiaryMask;
            } while (leftTertiary == 0);

            int rightLower32, rightTertiary;
            do {
                rightLower32 = (int) right.getCE(rightIndex++);
                anyQuaternaries |= rightLower32;
                assert ((rightLower32 & Collation.ONLY_TERTIARY_MASK) != 0 || (rightLower32 & 0xc0c0) == 0);
                rightTertiary = rightLower32 & tertiaryMask;
            } while (rightTertiary == 0);

            if (leftTertiary != rightTertiary) {
                if (CollationSettings.sortsTertiaryUpperCaseFirst(options)) {
                    // Pass through NO_CE and keep real tertiary weights larger than that.
                    // Do not change the artificial uppercase weight of a tertiary CE (0.0.ut),
                    // to keep tertiary CEs well-formed.
                    // Their case+tertiary weights must be greater than those of
                    // primary and secondary CEs.
                    if (leftTertiary > Collation.NO_CE_WEIGHT16) {
                        if ((leftLower32 & 0xffff0000) != 0) {
                            leftTertiary ^= 0xc000;
                        } else {
                            leftTertiary += 0x4000;
                        }
                    }
                    if (rightTertiary > Collation.NO_CE_WEIGHT16) {
                        if ((rightLower32 & 0xffff0000) != 0) {
                            rightTertiary ^= 0xc000;
                        } else {
                            rightTertiary += 0x4000;
                        }
                    }
                }
                return (leftTertiary < rightTertiary) ? Collation.LESS : Collation.GREATER;
            }
            if (leftTertiary == Collation.NO_CE_WEIGHT16) {
                break;
            }
        }
        if (CollationSettings.getStrength(options) <= Collator.TERTIARY) {
            return Collation.EQUAL;
        }

        if (!anyVariable && (anyQuaternaries & 0xc0) == 0) {
            // If there are no "variable" CEs and no non-zero quaternary weights,
            // then there are no quaternary differences.
            return Collation.EQUAL;
        }

        leftIndex = 0;
        rightIndex = 0;
        for (;;) {
            long leftQuaternary;
            do {
                long ce = left.getCE(leftIndex++);
                leftQuaternary = ce & 0xffff;
                if (leftQuaternary <= Collation.NO_CE_WEIGHT16) {
                    // Variable primary or completely ignorable or NO_CE.
                    leftQuaternary = ce >>> 32;
                } else {
                    // Regular CE, not tertiary ignorable.
                    // Preserve the quaternary weight in bits 7..6.
                    leftQuaternary |= 0xffffff3fL;
                }
            } while (leftQuaternary == 0);

            long rightQuaternary;
            do {
                long ce = right.getCE(rightIndex++);
                rightQuaternary = ce & 0xffff;
                if (rightQuaternary <= Collation.NO_CE_WEIGHT16) {
                    // Variable primary or completely ignorable or NO_CE.
                    rightQuaternary = ce >>> 32;
                } else {
                    // Regular CE, not tertiary ignorable.
                    // Preserve the quaternary weight in bits 7..6.
                    rightQuaternary |= 0xffffff3fL;
                }
            } while (rightQuaternary == 0);

            if (leftQuaternary != rightQuaternary) {
                // Return the difference, with script reordering.
                if (settings.hasReordering()) {
                    leftQuaternary = settings.reorder(leftQuaternary);
                    rightQuaternary = settings.reorder(rightQuaternary);
                }
                return (leftQuaternary < rightQuaternary) ? Collation.LESS : Collation.GREATER;
            }
            if (leftQuaternary == Collation.NO_CE_PRIMARY) {
                break;
            }
        }
        return Collation.EQUAL;
    }
}