/*

 * AboutOss is an utility library to retrieve and display

 * opensource licenses in Android applications.

 *

 * Copyright (C) 2023 by Frederic-Charles Barthelery.

 *

 * This file is part of AboutOss.

 *

 * AboutOss is free software: you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation, either version 3 of the License, or

 * (at your option) any later version.

 *

 * AboutOss is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with AboutOss.  If not, see <http://www.gnu.org/licenses/>.

 */

package com.geekorum.aboutoss.core.gms

import okio.ByteString

import okio.Source

import okio.buffer

import okio.use

/**

 * Parse licences data generated by the "com.google.android.gms.oss-licenses-plugin" gradle plugin.

 */

class OssLicenseParser {

    /**

     * Parse licenses

     * @param [thirdPartyLicensesInput] is usually res/raw/third_party_licenses file

     * @param [thirdPartyLicensesMetadataInput] is usually res/raw/third_party_license_metadata file

     */

    fun parseLicenses(

        thirdPartyLicensesInput: Source, thirdPartyLicensesMetadataInput: Source

    ): Map<String, String> {

        val licenses = readLicensesFile(thirdPartyLicensesInput)

        return buildLicenseInfo(licenses, thirdPartyLicensesMetadataInput)

    }

    private fun readLicensesFile(thirdPartyLicensesInput: Source): ByteString {

        return thirdPartyLicensesInput.buffer().use {

            it.readByteString()

        }

    }

    private fun buildLicenseInfo(license: ByteString, thirdPartyLicensesMetadataInput: Source): Map<String, String> {

        return thirdPartyLicensesMetadataInput.buffer().use {

            buildMap {

                while (true) {

                    val line = it.readUtf8Line() ?: break

                    if (line.isNotBlank()) {

                        with(line.toLineParser()) {

                            val start = readStartIdx()

                            val length = readLength()

                            val dependency = readName()

                            val licenseTxt = license.substring(

                                beginIndex = start,

                                endIndex = start + length + 1

                            ).utf8()

                            put(dependency, licenseTxt)

                        }

                    }

                }

            }

        }

    }

    companion object

}

private class LicenseMetadataLineParser(

    private val line: String

) {

    private var idx = 0

    fun readStartIdx(): Int {

        val end = line.indexOf(':', startIndex = idx)

        val result = line.substring(idx, end).toInt()

        idx = end + 1

        return result

    }

    fun readLength(): Int {

        val end = line.indexOf(' ', startIndex = idx)

        val result = line.substring(idx, end).toInt()

        idx = end + 1

        return result

    }

    fun readName(): String {

        val result = line.substring(idx)

        idx = line.length + 1

        return result

    }

}

private fun String.toLineParser() = LicenseMetadataLineParser(this)