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/*
 * Copyright (c) 2024 Matthew Nelson
 *
 * 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
 *
 *     https://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.
 **/
@file:Suppress("EXPECT_ACTUAL_CLASSIFIERS_ARE_IN_BETA_WARNING")

package io.matthewnelson.kmp.process

/**
 * For internal usage only.
 *
 * Wrapper class for buffering data to utilize in platform specific
 * implementations along with [LineOutputFeed], primarily in order
 * to mitigate unnecessarily copying a `Node.js` Buffer to a ByteArray.
 *
 * @see [LineOutputFeed]
 * */
public expect value class ReadBuffer private constructor(private val _buf: Any) {

    internal fun capacity(): Int

    @Throws(IndexOutOfBoundsException::class)
    internal operator fun get(index: Int): Byte

    @Throws(IllegalArgumentException::class, IndexOutOfBoundsException::class)
    internal fun decodeToUtf8(startIndex: Int, endIndex: Int): String

    /**
     * Scans buffered input and dispatches lines, disregarding
     * line breaks CR (`\r`), LF (`\n`), & CRLF (`\r\n`).
     *
     * After reading operations are exhausted, calling [close] will
     * assume any buffered input remaining is terminating and dispatch
     * it as a line, and then dispatch `null` to indicate End Of Stream.
     *
     * This is **NOT** thread safe.
     *
     * e.g. (Jvm)
     *
     *     val feed = ReadBuffer.lineOutputFeed { line ->
     *         println(line ?: "--EOS--")
     *     }
     *
     *     myInputStream.use { iStream ->
     *         val buf = ReadBuffer.allocate()
     *
     *         try {
     *             while(true) {
     *                 val read = iStream.read(buf.buf)
     *                 if (read == -1) break
     *                 feed.onData(buf, read)
     *             }
     *         } finally {
     *
     *             // done reading, dispatch last line
     *             // (if buffered), and dispatch null
     *             // to indicate EOS
     *             feed.close()
     *         }
     *     }
     *
     * @see [lineOutputFeed]
     * */
    public abstract class LineOutputFeed internal constructor() {

        @Throws(IllegalArgumentException::class, IndexOutOfBoundsException::class, IllegalStateException::class)
        public abstract fun onData(buf: ReadBuffer, len: Int)

        public abstract fun close()
    }

    public companion object {

        /**
         * Allocates a new buffer with capacity of (8 * 1024) bytes
         * */
        @InternalProcessApi
        public fun allocate(): ReadBuffer

        /**
         * Creates a new [LineOutputFeed]
         *
         * **NOTE:** [dispatch] should not throw exception
         * */
        @InternalProcessApi
        public fun lineOutputFeed(dispatch: (line: String?) -> Unit): LineOutputFeed
    }
}