/*
 * Copyright (C) 2015 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.
 */

#include <cstdlib>
#include <string>
#include <vector>

#include <cutils/log.h>
#include <unicode/utf.h>
#include <unicode/utf8.h>

#include "minikin/U16StringPiece.h"

namespace minikin {

// src is of the form "U+1F431 | 'h' 'i'". Position of "|" gets saved to offset if non-null.
// Size is returned in an out parameter because gtest needs a void return for ASSERT to work.
void ParseUnicode(uint16_t* buf, size_t buf_size, const char* src, size_t* result_size,
                  size_t* offset) {
    size_t input_ix = 0;
    size_t output_ix = 0;
    bool seen_offset = false;

    while (src[input_ix] != 0) {
        switch (src[input_ix]) {
            case '\'':
                // single ASCII char
                LOG_ALWAYS_FATAL_IF(static_cast<uint8_t>(src[input_ix]) >= 0x80);
                input_ix++;
                LOG_ALWAYS_FATAL_IF(src[input_ix] == 0);
                LOG_ALWAYS_FATAL_IF(output_ix >= buf_size);
                buf[output_ix++] = (uint16_t)src[input_ix++];
                LOG_ALWAYS_FATAL_IF(src[input_ix] != '\'');
                input_ix++;
                break;
            case 'u':
            case 'U': {
                // Unicode codepoint in hex syntax
                input_ix++;
                LOG_ALWAYS_FATAL_IF(src[input_ix] != '+');
                input_ix++;
                char* endptr = (char*)src + input_ix;
                unsigned long int codepoint = strtoul(src + input_ix, &endptr, 16);
                size_t num_hex_digits = endptr - (src + input_ix);

                // also triggers on invalid number syntax, digits = 0
                LOG_ALWAYS_FATAL_IF(num_hex_digits < 4u);
                LOG_ALWAYS_FATAL_IF(num_hex_digits > 6u);
                LOG_ALWAYS_FATAL_IF(codepoint > 0x10FFFFu);
                input_ix += num_hex_digits;
                if (U16_LENGTH(codepoint) == 1) {
                    LOG_ALWAYS_FATAL_IF(output_ix + 1 > buf_size);
                    buf[output_ix++] = codepoint;
                } else {
                    // UTF-16 encoding
                    LOG_ALWAYS_FATAL_IF(output_ix + 2 > buf_size);
                    buf[output_ix++] = U16_LEAD(codepoint);
                    buf[output_ix++] = U16_TRAIL(codepoint);
                }
                break;
            }
            case ' ':
                input_ix++;
                break;
            case '|':
                LOG_ALWAYS_FATAL_IF(seen_offset);
                LOG_ALWAYS_FATAL_IF(offset == nullptr);
                *offset = output_ix;
                seen_offset = true;
                input_ix++;
                break;
            default:
                LOG_ALWAYS_FATAL("Unexpected Character");
        }
    }
    LOG_ALWAYS_FATAL_IF(result_size == nullptr);
    *result_size = output_ix;
    LOG_ALWAYS_FATAL_IF(!seen_offset && offset != nullptr);
}

std::vector<uint16_t> parseUnicodeStringWithOffset(const std::string& in, size_t* offset) {
    std::unique_ptr<uint16_t[]> buffer(new uint16_t[in.size()]);
    size_t result_size = 0;
    ParseUnicode(buffer.get(), in.size(), in.c_str(), &result_size, offset);
    return std::vector<uint16_t>(buffer.get(), buffer.get() + result_size);
}

std::vector<uint16_t> parseUnicodeString(const std::string& in) {
    return parseUnicodeStringWithOffset(in, nullptr);
}

std::vector<uint16_t> utf8ToUtf16(const std::string& text) {
    std::vector<uint16_t> result;
    int32_t i = 0;
    const int32_t textLength = static_cast<int32_t>(text.size());
    uint32_t c = 0;
    while (i < textLength) {
        U8_NEXT(text.c_str(), i, textLength, c);
        if (U16_LENGTH(c) == 1) {
            result.push_back(c);
        } else {
            result.push_back(U16_LEAD(c));
            result.push_back(U16_TRAIL(c));
        }
    }
    return result;
}

std::string utf16ToUtf8(const U16StringPiece& u16String) {
    const uint32_t textLength = u16String.size();
    uint32_t i = 0;
    uint32_t c = 0;

    std::string out;
    out.reserve(textLength * 4);

    while (i < textLength) {
        U16_NEXT(u16String.data(), i, textLength, c);

        char buf[U8_MAX_LENGTH] = {};
        uint32_t outIndex = 0;
        U8_APPEND_UNSAFE(buf, outIndex, c);
        out.append(buf, outIndex);
    }
    return out;
}

}  // namespace minikin