chore: organize code

Author: phaux

lib/index.js

@@ -1,5 +1,6 @@
-import { spawn } from "node:child_process"
 import debug from "debug"
+import assert from "node:assert"
+import { spawn } from "node:child_process"
 import { createReadStream, createWriteStream } from "node:fs"
 import { unlink } from "node:fs/promises"
 import { tmpdir } from "node:os"
@@ -9,93 +10,6 @@ import { PassThrough } from "node:stream"
 const dbg = debug("ffmpeg-stream")
 const EXIT_CODES = [0, 255]
 
-/**
- * @param {import("node:stream").Readable | import("node:stream").Writable} stream
- * @param {string} name
- */
-function debugStream(stream, name) {
-  stream.on("error", err => {
-    dbg(`${name} error: ${err.message}`)
-  })
-  stream.on(
-    "data",
-    /** @type {(data: Buffer | string) => void} */ data => {
-      dbg(`${name} data: ${data.length} bytes`)
-    },
-  )
-  stream.on("finish", () => {
-    dbg(`${name} finish`)
-  })
-}
-
-/**
- * @param {string} [prefix]
- * @param {string} [suffix]
- */
-function getTmpPath(prefix = "", suffix = "") {
-  const dir = tmpdir()
-  const id = Math.random().toString(32).substr(2, 10)
-  return join(dir, `${prefix}${id}${suffix}`)
-}
-
-/**
- * FFmpeg options object.
- *
- * These are the same options that you normally pass to the ffmpeg command in the terminal.
- * Documentation for individual options can be found in the [ffmpeg docs](https://ffmpeg.org/ffmpeg.html#Main-options).
- *
- * To specify a boolean option, set it to `true`.
- * To specify an option multiple times, use an array.
- * Options with nullish or `false` values are ignored.
- *
- * @example
- *
- * ```js
- * const options = { f: "image2", vcodec: "png" }
- * ```
- *
- * @typedef {Record<string, string | number | boolean | Array<string | null | undefined> | null | undefined>} ConverterOptions
- */
-
-/**
- * @ignore
- * @internal
- * @typedef {Object} ConverterPipe
- * @property {"input" | "output"} type
- * @property {ConverterOptions} options
- * @property {string} file
- * @property {() => Promise<void>} [onBegin]
- * @property {(process: import("node:child_process").ChildProcess) => void} [onSpawn]
- * @property {() => Promise<void>} [onFinish]
- */
-
-/**
- * @param {ConverterOptions} options
- * @returns {string[]}
- */
-function getArgs(options) {
-  /** @type {string[]} */
-  const args = []
-
-  for (const [option, value] of Object.entries(options)) {
-    if (Array.isArray(value)) {
-      for (const element of value) {
-        if (element != null) {
-          args.push(`-${option}`)
-          args.push(String(element))
-        }
-      }
-    } else if (value != null && value !== false) {
-      args.push(`-${option}`)
-      if (typeof value != "boolean") {
-        args.push(String(value))
-      }
-    }
-  }
-
-  return args
-}
-
 /**
  * A class which wraps a FFmpeg process.
  *
@@ -154,7 +68,7 @@ export class Converter {
    * This builds a command like the one you would normally use in the terminal.
    *
    * @param {string} file Path to the input file.
-   * @param {ConverterOptions} [options] FFmpeg options for this input.
+   * @param {ConverterPipeOptions} [options] FFmpeg options for this input.
    *
    * @example
    *
@@ -183,7 +97,7 @@ export class Converter {
    * This builds a command like the one you would normally use in the terminal.
    *
    * @param {string} file Path to the output file.
-   * @param {ConverterOptions} [options] FFmpeg options for this output.
+   * @param {ConverterPipeOptions} [options] FFmpeg options for this output.
    *
    * @example
    *
@@ -211,9 +125,10 @@ export class Converter {
    *
    * Internally, it adds a special `pipe:<number>` input argument to the FFmpeg command.
    *
-   * Remember to specify the [`f` option](https://ffmpeg.org/ffmpeg.html#Main-options), which specifies the format of the input data.
+   * Remember to specify the [`f` option](https://ffmpeg.org/ffmpeg.html#Main-options),
+   * which specifies the format of the input data.
    *
-   * @param {ConverterOptions} options FFmpeg options for this input.
+   * @param {ConverterPipeOptions} options FFmpeg options for this input.
    * @returns {import("node:stream").Writable} A stream which will be written to the FFmpeg process' stdio.
    *
    * @example
@@ -255,9 +170,10 @@ export class Converter {
    *
    * Internally, it adds a special `pipe:<number>` output argument to the FFmpeg command.
    *
-   * Remember to specify the [`f` option](https://ffmpeg.org/ffmpeg.html#Main-options), which specifies the format of the output data.
+   * Remember to specify the [`f` option](https://ffmpeg.org/ffmpeg.html#Main-options),
+   * which specifies the format of the output data.
    *
-   * @param {ConverterOptions} options FFmpeg options for this output.
+   * @param {ConverterPipeOptions} options FFmpeg options for this output.
    * @returns {import("node:stream").Readable} A stream which will be read from the FFmpeg process' stdio.
    *
    * @example
@@ -299,7 +215,7 @@ export class Converter {
    *
    * Use this method if the format you want to read doesn't support non-seekable input.
    *
-   * @param {ConverterOptions} options FFmpeg options for this input.
+   * @param {ConverterPipeOptions} options FFmpeg options for this input.
    * @returns {import("node:stream").Writable} A stream which will be written to the temporary file.
    */
   createBufferedInputStream(options) {
@@ -338,7 +254,7 @@ export class Converter {
    *
    * Use this method if the format you want to write doesn't support non-seekable output.
    *
-   * @param {ConverterOptions} options FFmpeg options for this output.
+   * @param {ConverterPipeOptions} options FFmpeg options for this output.
    * @returns {import("node:stream").Readable} A stream which will be read from the temporary file.
    */
   createBufferedOutputStream(options) {
@@ -384,11 +300,11 @@ export class Converter {
         pipes.push(pipe)
       }
 
-      const command = this.getSpawnArgs()
+      const args = this.getSpawnArgs()
       const stdio = this.getStdioArg()
-      dbg(`spawn: ${this.ffmpegPath} ${command.join(" ")}`)
+      dbg(`spawn: ${this.ffmpegPath} ${args.join(" ")}`)
       dbg(`spawn stdio: ${stdio.join(" ")}`)
-      this.process = spawn(this.ffmpegPath, command, { stdio })
+      this.process = spawn(this.ffmpegPath, args, { stdio })
       const finished = this.handleProcess()
 
       for (const pipe of this.pipes) {
@@ -427,6 +343,7 @@ export class Converter {
   }
 
   /**
+   * Returns stdio pipes which can be passed to {@link spawn}.
    * @private
    * @returns {Array<"ignore" | "pipe">}
    */
@@ -440,25 +357,26 @@ export class Converter {
   }
 
   /**
+   * Returns arguments which can be passed to {@link spawn}.
    * @private
    * @returns {string[]}
    */
   getSpawnArgs() {
     /** @type {string[]} */
-    const command = []
+    const args = []
 
     for (const pipe of this.pipes) {
       if (pipe.type !== "input") continue
-      command.push(...getArgs(pipe.options))
-      command.push("-i", pipe.file)
+      args.push(...stringifyArgs(pipe.options))
+      args.push("-i", pipe.file)
     }
     for (const pipe of this.pipes) {
       if (pipe.type !== "output") continue
-      command.push(...getArgs(pipe.options))
-      command.push(pipe.file)
+      args.push(...stringifyArgs(pipe.options))
+      args.push(pipe.file)
     }
 
-    return command
+    return args
   }
 
   /**
@@ -470,7 +388,7 @@ export class Converter {
       /** @type {string[]} */
       const logLines = []
 
-      if (this.process == null) return reject(Error(`Converter not started`))
+      assert(this.process != null, "process should be initialized")
 
       if (this.process.stderr != null) {
         this.process.stderr.setEncoding("utf8")
@@ -509,3 +427,96 @@ export class Converter {
     })
   }
 }
+
+/**
+ * Stringifies FFmpeg options object into command line arguments array.
+ *
+ * @param {ConverterPipeOptions} options
+ * @returns {string[]}
+ */
+function stringifyArgs(options) {
+  /** @type {string[]} */
+  const args = []
+
+  for (const [option, value] of Object.entries(options)) {
+    if (Array.isArray(value)) {
+      for (const element of value) {
+        if (element != null) {
+          args.push(`-${option}`)
+          args.push(String(element))
+        }
+      }
+    } else if (value != null && value !== false) {
+      args.push(`-${option}`)
+      if (typeof value != "boolean") {
+        args.push(String(value))
+      }
+    }
+  }
+
+  return args
+}
+
+/**
+ * Returns a random file path in the system's temporary directory.
+ *
+ * @param {string} [prefix]
+ * @param {string} [suffix]
+ */
+function getTmpPath(prefix = "", suffix = "") {
+  const dir = tmpdir()
+  const id = Math.random().toString(32).substr(2, 10)
+  return join(dir, `${prefix}${id}${suffix}`)
+}
+
+/**
+ * @param {import("node:stream").Readable | import("node:stream").Writable} stream
+ * @param {string} name
+ */
+function debugStream(stream, name) {
+  stream.on("error", err => {
+    dbg(`${name} error: ${err.message}`)
+  })
+  stream.on(
+    "data",
+    /** @type {(data: Buffer | string) => void} */ data => {
+      dbg(`${name} data: ${data.length} bytes`)
+    },
+  )
+  stream.on("finish", () => {
+    dbg(`${name} finish`)
+  })
+}
+
+/**
+ * Options object for a single input or output of a {@link Converter}.
+ *
+ * These are the same options that you normally pass to the ffmpeg command in the terminal.
+ * Documentation for individual options can be found in the [ffmpeg docs](https://ffmpeg.org/ffmpeg.html#Main-options).
+ *
+ * To specify a boolean option, set it to `true`.
+ * To specify an option multiple times, use an array.
+ * Options with nullish or `false` values are ignored.
+ *
+ * @example
+ *
+ * ```js
+ * const options = { f: "image2", vcodec: "png" }
+ * ```
+ *
+ * @typedef {Record<string, string | number | boolean | Array<string | null | undefined> | null | undefined>} ConverterPipeOptions
+ */
+
+/**
+ * Data about a single input or output of a {@link Converter}.
+ *
+ * @ignore
+ * @internal
+ * @typedef {Object} ConverterPipe
+ * @property {"input" | "output"} type
+ * @property {ConverterPipeOptions} options
+ * @property {string} file
+ * @property {() => Promise<void>} [onBegin]
+ * @property {(process: import("node:child_process").ChildProcess) => void} [onSpawn]
+ * @property {() => Promise<void>} [onFinish]
+ */