/*
 * Copyright (C) 2013 The Android Open Source Project
 *
 * 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 com.android.inputmethod.latin;

import android.text.InputType;
import android.text.TextUtils;

import java.util.Locale;

public final class CapsModeUtils {
    private CapsModeUtils() {
        // This utility class is not publicly instantiable.
    }

    /**
     * Apply an auto-caps mode to a string.
     *
     * This intentionally does NOT apply manual caps mode. It only changes the capitalization if
     * the mode is one of the auto-caps modes.
     * @param s The string to capitalize.
     * @param capitalizeMode The mode in which to capitalize.
     * @param locale The locale for capitalizing.
     * @return The capitalized string.
     */
    public static String applyAutoCapsMode(final String s, final int capitalizeMode,
            final Locale locale) {
        if (WordComposer.CAPS_MODE_AUTO_SHIFT_LOCKED == capitalizeMode) {
            return s.toUpperCase(locale);
        } else if (WordComposer.CAPS_MODE_AUTO_SHIFTED == capitalizeMode) {
            return StringUtils.capitalizeFirstCodePoint(s, locale);
        } else {
            return s;
        }
    }

    /**
     * Return whether a constant represents an auto-caps mode (either auto-shift or auto-shift-lock)
     * @param mode The mode to test for
     * @return true if this represents an auto-caps mode, false otherwise
     */
    public static boolean isAutoCapsMode(final int mode) {
        return WordComposer.CAPS_MODE_AUTO_SHIFTED == mode
                || WordComposer.CAPS_MODE_AUTO_SHIFT_LOCKED == mode;
    }

    /**
     * Determine what caps mode should be in effect at the current offset in
     * the text. Only the mode bits set in <var>reqModes</var> will be
     * checked. Note that the caps mode flags here are explicitly defined
     * to match those in {@link InputType}.
     *
     * This code is a straight copy of TextUtils.getCapsMode (modulo namespace and formatting
     * issues). This will change in the future as we simplify the code for our use and fix bugs.
     *
     * @param cs The text that should be checked for caps modes.
     * @param reqModes The modes to be checked: may be any combination of
     * {@link TextUtils#CAP_MODE_CHARACTERS}, {@link TextUtils#CAP_MODE_WORDS}, and
     * {@link TextUtils#CAP_MODE_SENTENCES}.
     * @param locale The locale to consider for capitalization rules
     * @param hasSpaceBefore Whether we should consider there is a space inserted at the end of cs
     *
     * @return Returns the actual capitalization modes that can be in effect
     * at the current position, which is any combination of
     * {@link TextUtils#CAP_MODE_CHARACTERS}, {@link TextUtils#CAP_MODE_WORDS}, and
     * {@link TextUtils#CAP_MODE_SENTENCES}.
     */
    public static int getCapsMode(final CharSequence cs, final int reqModes, final Locale locale,
            final boolean hasSpaceBefore) {
        // Quick description of what we want to do:
        // CAP_MODE_CHARACTERS is always on.
        // CAP_MODE_WORDS is on if there is some whitespace before the cursor.
        // CAP_MODE_SENTENCES is on if there is some whitespace before the cursor, and the end
        //   of a sentence just before that.
        // We ignore opening parentheses and the like just before the cursor for purposes of
        // finding whitespace for WORDS and SENTENCES modes.
        // The end of a sentence ends with a period, question mark or exclamation mark. If it's
        // a period, it also needs not to be an abbreviation, which means it also needs to either
        // be immediately preceded by punctuation, or by a string of only letters with single
        // periods interleaved.

        // Step 1 : check for cap MODE_CHARACTERS. If it's looked for, it's always on.
        if ((reqModes & (TextUtils.CAP_MODE_WORDS | TextUtils.CAP_MODE_SENTENCES)) == 0) {
            // Here we are not looking for MODE_WORDS or MODE_SENTENCES, so since we already
            // evaluated MODE_CHARACTERS, we can return.
            return TextUtils.CAP_MODE_CHARACTERS & reqModes;
        }

        // Step 2 : Skip (ignore at the end of input) any opening punctuation. This includes
        // opening parentheses, brackets, opening quotes, everything that *opens* a span of
        // text in the linguistic sense. In RTL languages, this is still an opening sign, although
        // it may look like a right parenthesis for example. We also include double quote and
        // single quote since they aren't start punctuation in the unicode sense, but should still
        // be skipped for English. TODO: does this depend on the language?
        int i;
        if (hasSpaceBefore) {
            i = cs.length() + 1;
        } else {
            for (i = cs.length(); i > 0; i--) {
                final char c = cs.charAt(i - 1);
                if (c != Constants.CODE_DOUBLE_QUOTE && c != Constants.CODE_SINGLE_QUOTE
                        && Character.getType(c) != Character.START_PUNCTUATION) {
                    break;
                }
            }
        }

        // We are now on the character that precedes any starting punctuation, so in the most
        // frequent case this will be whitespace or a letter, although it may occasionally be a
        // start of line, or some symbol.

        // Step 3 : Search for the start of a paragraph. From the starting point computed in step 2,
        // we go back over any space or tab char sitting there. We find the start of a paragraph
        // if the first char that's not a space or tab is a start of line (as in \n, start of text,
        // or some other similar characters).
        int j = i;
        char prevChar = Constants.CODE_SPACE;
        if (hasSpaceBefore) --j;
        while (j > 0) {
            prevChar = cs.charAt(j - 1);
            if (!Character.isSpaceChar(prevChar) && prevChar != Constants.CODE_TAB) break;
            j--;
        }
        if (j <= 0 || Character.isWhitespace(prevChar)) {
            // There are only spacing chars between the start of the paragraph and the cursor,
            // defined as a isWhitespace() char that is neither a isSpaceChar() nor a tab. Both
            // MODE_WORDS and MODE_SENTENCES should be active.
            return (TextUtils.CAP_MODE_CHARACTERS | TextUtils.CAP_MODE_WORDS
                    | TextUtils.CAP_MODE_SENTENCES) & reqModes;
        }
        if (i == j) {
            // If we don't have whitespace before index i, it means neither MODE_WORDS
            // nor mode sentences should be on so we can return right away.
            return TextUtils.CAP_MODE_CHARACTERS & reqModes;
        }
        if ((reqModes & TextUtils.CAP_MODE_SENTENCES) == 0) {
            // Here we know we have whitespace before the cursor (if not, we returned in the above
            // if i == j clause), so we need MODE_WORDS to be on. And we don't need to evaluate
            // MODE_SENTENCES so we can return right away.
            return (TextUtils.CAP_MODE_CHARACTERS | TextUtils.CAP_MODE_WORDS) & reqModes;
        }
        // Please note that because of the reqModes & CAP_MODE_SENTENCES test a few lines above,
        // we know that MODE_SENTENCES is being requested.

        // Step 4 : Search for MODE_SENTENCES.
        // English is a special case in that "American typography" rules, which are the most common
        // in English, state that a sentence terminator immediately following a quotation mark
        // should be swapped with it and de-duplicated (included in the quotation mark),
        // e.g. <<Did he say, "let's go home?">>
        // No other language has such a rule as far as I know, instead putting inside the quotation
        // mark as the exact thing quoted and handling the surrounding punctuation independently,
        // e.g. <<Did he say, "let's go home"?>>
        // Hence, specifically for English, we treat this special case here.
        if (Locale.ENGLISH.getLanguage().equals(locale.getLanguage())) {
            for (; j > 0; j--) {
                // Here we look to go over any closing punctuation. This is because in dominant
                // variants of English, the final period is placed within double quotes and maybe
                // other closing punctuation signs. This is generally not true in other languages.
                final char c = cs.charAt(j - 1);
                if (c != Constants.CODE_DOUBLE_QUOTE && c != Constants.CODE_SINGLE_QUOTE
                        && Character.getType(c) != Character.END_PUNCTUATION) {
                    break;
                }
            }
        }

        if (j <= 0) return TextUtils.CAP_MODE_CHARACTERS & reqModes;
        char c = cs.charAt(--j);

        // We found the next interesting chunk of text ; next we need to determine if it's the
        // end of a sentence. If we have a question mark or an exclamation mark, it's the end of
        // a sentence. If it's neither, the only remaining case is the period so we get the opposite
        // case out of the way.
        if (c == Constants.CODE_QUESTION_MARK || c == Constants.CODE_EXCLAMATION_MARK) {
            return (TextUtils.CAP_MODE_CHARACTERS | TextUtils.CAP_MODE_SENTENCES) & reqModes;
        }
        if (c != Constants.CODE_PERIOD || j <= 0) {
            return (TextUtils.CAP_MODE_CHARACTERS | TextUtils.CAP_MODE_WORDS) & reqModes;
        }

        // We found out that we have a period. We need to determine if this is a full stop or
        // otherwise sentence-ending period, or an abbreviation like "e.g.". An abbreviation
        // looks like (\w\.){2,}
        // To find out, we will have a simple state machine with the following states :
        // START, WORD, PERIOD, ABBREVIATION
        // On START : (just before the first period)
        //           letter => WORD
        //           whitespace => end with no caps (it was a stand-alone period)
        //           otherwise => end with caps (several periods/symbols in a row)
        // On WORD : (within the word just before the first period)
        //           letter => WORD
        //           period => PERIOD
        //           otherwise => end with caps (it was a word with a full stop at the end)
        // On PERIOD : (period within a potential abbreviation)
        //           letter => LETTER
        //           otherwise => end with caps (it was not an abbreviation)
        // On LETTER : (letter within a potential abbreviation)
        //           letter => LETTER
        //           period => PERIOD
        //           otherwise => end with no caps (it was an abbreviation)
        // "Not an abbreviation" in the above chart essentially covers cases like "...yes.". This
        // should capitalize.

        final int START = 0;
        final int WORD = 1;
        final int PERIOD = 2;
        final int LETTER = 3;
        final int caps = (TextUtils.CAP_MODE_CHARACTERS | TextUtils.CAP_MODE_WORDS
                | TextUtils.CAP_MODE_SENTENCES) & reqModes;
        final int noCaps = (TextUtils.CAP_MODE_CHARACTERS | TextUtils.CAP_MODE_WORDS) & reqModes;
        int state = START;
        while (j > 0) {
            c = cs.charAt(--j);
            switch (state) {
            case START:
                if (Character.isLetter(c)) {
                    state = WORD;
                } else if (Character.isWhitespace(c)) {
                    return noCaps;
                } else {
                    return caps;
                }
                break;
            case WORD:
                if (Character.isLetter(c)) {
                    state = WORD;
                } else if (c == Constants.CODE_PERIOD) {
                    state = PERIOD;
                } else {
                    return caps;
                }
                break;
            case PERIOD:
                if (Character.isLetter(c)) {
                    state = LETTER;
                } else {
                    return caps;
                }
                break;
            case LETTER:
                if (Character.isLetter(c)) {
                    state = LETTER;
                } else if (c == Constants.CODE_PERIOD) {
                    state = PERIOD;
                } else {
                    return noCaps;
                }
            }
        }
        // Here we arrived at the start of the line. This should behave exactly like whitespace.
        return (START == state || LETTER == state) ? noCaps : caps;
    }
}