package com.jsoniter;

import com.jsoniter.any.Any;

import java.io.IOException;

class IterImpl {

    public static final int readObjectFieldAsHash(JsonIterator iter) throws IOException {
        if (nextToken(iter) != '"') {
            throw iter.reportError("readObjectFieldAsHash", "expect \"");
        }
        long hash = 0x811c9dc5;
        for (int i = iter.head; i < iter.tail; i++) {
            byte c = iter.buf[i];
            if (c == '"') {
                iter.head = i + 1;
                if (nextToken(iter) != ':') {
                    throw iter.reportError("readObjectFieldAsHash", "expect :");
                }
                return (int) hash;
            }
            hash ^= c;
            hash *= 0x1000193;
        }
        throw iter.reportError("readObjectFieldAsHash", "unmatched quote");
    }

    public static final Slice readObjectFieldAsSlice(JsonIterator iter) throws IOException {
        Slice field = readSlice(iter);
        if (nextToken(iter) != ':') {
            throw iter.reportError("readObjectFieldAsSlice", "expect : after object field");
        }
        return field;
    }

    final static void skipArray(JsonIterator iter) throws IOException {
        int level = 1;
        for (int i = iter.head; i < iter.tail; i++) {
            switch (iter.buf[i]) {
                case '"': // If inside string, skip it
                    iter.head = i + 1;
                    skipString(iter);
                    i = iter.head - 1; // it will be i++ soon
                    break;
                case '[': // If open symbol, increase level
                    level++;
                    break;
                case ']': // If close symbol, increase level
                    level--;

                    // If we have returned to the original level, we're done
                    if (level == 0) {
                        iter.head = i + 1;
                        return;
                    }
                    break;
            }
        }
        throw iter.reportError("skipArray", "incomplete array");
    }

    final static void skipObject(JsonIterator iter) throws IOException {
        int level = 1;
        for (int i = iter.head; i < iter.tail; i++) {
            switch (iter.buf[i]) {
                case '"': // If inside string, skip it
                    iter.head = i + 1;
                    skipString(iter);
                    i = iter.head - 1; // it will be i++ soon
                    break;
                case '{': // If open symbol, increase level
                    level++;
                    break;
                case '}': // If close symbol, increase level
                    level--;

                    // If we have returned to the original level, we're done
                    if (level == 0) {
                        iter.head = i + 1;
                        return;
                    }
                    break;
            }
        }
        throw iter.reportError("skipObject", "incomplete object");
    }

    final static void skipString(JsonIterator iter) throws IOException {
        int end = IterImplSkip.findStringEnd(iter);
        if (end == -1) {
            throw iter.reportError("skipString", "incomplete string");
        } else {
            iter.head = end;
        }
    }

    final static void skipUntilBreak(JsonIterator iter) throws IOException {
        // true, false, null, number
        for (int i = iter.head; i < iter.tail; i++) {
            byte c = iter.buf[i];
            if (IterImplSkip.breaks[c]) {
                iter.head = i;
                return;
            }
        }
        iter.head = iter.tail;
    }

    final static boolean skipNumber(JsonIterator iter) throws IOException {
        // true, false, null, number
        boolean dotFound = false;
        for (int i = iter.head; i < iter.tail; i++) {
            byte c = iter.buf[i];
            if (c == '.') {
                dotFound = true;
                continue;
            }
            if (IterImplSkip.breaks[c]) {
                iter.head = i;
                return dotFound;
            }
        }
        iter.head = iter.tail;
        return dotFound;
    }

    // read the bytes between " "
    public final static Slice readSlice(JsonIterator iter) throws IOException {
        if (IterImpl.nextToken(iter) != '"') {
            throw iter.reportError("readSlice", "expect \" for string");
        }
        int end = IterImplString.findSliceEnd(iter);
        if (end == -1) {
            throw iter.reportError("readSlice", "incomplete string");
        } else {
            // reuse current buffer
            iter.reusableSlice.reset(iter.buf, iter.head, end - 1);
            iter.head = end;
            return iter.reusableSlice;
        }
    }

    final static byte nextToken(JsonIterator iter) throws IOException {
        int i = iter.head;
        try {
            for (; ; ) {
                byte c = iter.buf[i++];
                switch (c) {
                    case ' ':
                    case '\n':
                    case '\r':
                    case '\t':
                        continue;
                    default:
                        if (i > iter.tail) {
                            iter.head = iter.tail;
                            return 0;
                        }
                        iter.head = i;
                        return c;
                }
            }
        } catch (IndexOutOfBoundsException e) {
            iter.head = iter.tail;
            return 0;
        }
    }

    final static byte readByte(JsonIterator iter) throws IOException {
        if (iter.head == iter.tail) {
            return 0;
        }
        return iter.buf[iter.head++];
    }

    public static Any readAny(JsonIterator iter) throws IOException {
        int start = iter.head;
        byte c = nextToken(iter);
        switch (c) {
            case '"':
                skipString(iter);
                return Any.lazyString(iter.buf, start, iter.head);
            case 't':
                skipFixedBytes(iter, 3);
                return Any.wrap(true);
            case 'f':
                skipFixedBytes(iter, 4);
                return Any.wrap(false);
            case 'n':
                skipFixedBytes(iter, 3);
                return Any.wrap((Object) null);
            case '[':
                skipArray(iter);
                return Any.lazyArray(iter.buf, start, iter.head);
            case '{':
                skipObject(iter);
                return Any.lazyObject(iter.buf, start, iter.head);
            default:
                if (skipNumber(iter)) {
                    return Any.lazyDouble(iter.buf, start, iter.head);
                } else {
                    return Any.lazyLong(iter.buf, start, iter.head);
                }
        }
    }

    public static void skipFixedBytes(JsonIterator iter, int n) throws IOException {
        iter.head += n;
    }

    public final static boolean loadMore(JsonIterator iter) throws IOException {
        return false;
    }

    public final static String readStringSlowPath(JsonIterator iter, int j) throws IOException {
        try {
            for (int i = iter.head; i < iter.tail; ) {
                int bc = iter.buf[i++];
                if (bc == '"') {
                    return new String(iter.reusableChars, 0, j);
                }
                if (bc == '\\') {
                    bc = iter.buf[i++];
                    switch (bc) {
                        case 'b':
                            bc = '\b';
                            break;
                        case 't':
                            bc = '\t';
                            break;
                        case 'n':
                            bc = '\n';
                            break;
                        case 'f':
                            bc = '\f';
                            break;
                        case 'r':
                            bc = '\r';
                            break;
                        case '"':
                        case '/':
                        case '\\':
                            break;
                        case 'u':
                            bc = (IterImplString.translateHex(iter.buf[i++]) << 12) +
                                    (IterImplString.translateHex(iter.buf[i++]) << 8) +
                                    (IterImplString.translateHex(iter.buf[i++]) << 4) +
                                    IterImplString.translateHex(iter.buf[i++]);
                            break;

                        default:
                            throw iter.reportError("readStringSlowPath", "invalid escape character: " + bc);
                    }
                } else if ((bc & 0x80) != 0) {
                    final int u2 = iter.buf[i++];
                    if ((bc & 0xE0) == 0xC0) {
                        bc = ((bc & 0x1F) << 6) + (u2 & 0x3F);
                    } else {
                        final int u3 = iter.buf[i++];
                        if ((bc & 0xF0) == 0xE0) {
                            bc = ((bc & 0x0F) << 12) + ((u2 & 0x3F) << 6) + (u3 & 0x3F);
                        } else {
                            final int u4 = iter.buf[i++];
                            if ((bc & 0xF8) == 0xF0) {
                                bc = ((bc & 0x07) << 18) + ((u2 & 0x3F) << 12) + ((u3 & 0x3F) << 6) + (u4 & 0x3F);
                            } else {
                                throw iter.reportError("readStringSlowPath", "invalid unicode character");
                            }

                            if (bc >= 0x10000) {
                                // check if valid unicode
                                if (bc >= 0x110000)
                                    throw iter.reportError("readStringSlowPath", "invalid unicode character");

                                // split surrogates
                                final int sup = bc - 0x10000;
                                iter.reusableChars[j++] = (char) ((sup >>> 10) + 0xd800);
                                iter.reusableChars[j++] = (char) ((sup & 0x3ff) + 0xdc00);
                                continue;
                            }
                        }
                    }
                }
                iter.reusableChars[j++] = (char) bc;
            }
            throw iter.reportError("readStringSlowPath", "incomplete string");
        } catch (IndexOutOfBoundsException e) {
            throw iter.reportError("readString", "incomplete string");
        }
    }
}