[Artifacts] Name validation + zip specification creation (#1482)

* Artifact name validation + zip specification creation

* Fix linting issues

* Grammar fix

* Update test description

packages/artifact/src/internal/upload/upload-zip-specification.ts

@@ -0,0 +1,111 @@
+import * as fs from 'fs'
+import {info} from '@actions/core'
+import {normalize, resolve} from 'path'
+import {validateFilePath} from './path-and-artifact-name-validation'
+
+export interface UploadZipSpecification {
+  /**
+   * An absolute source path that points to a file that will be added to a zip. Null if creating a new directory
+   */
+  sourcePath: string | null
+
+  /**
+   * The destination path in a zip for a file
+   */
+  destinationPath: string
+}
+
+/**
+ * Checks if a root directory exists and is valid
+ * @param rootDirectory an absolute root directory path common to all input files that that will be trimmed from the final zip structure
+ */
+export function validateRootDirectory(rootDirectory: string): void {
+  if (!fs.existsSync(rootDirectory)) {
+    throw new Error(
+      `The provided rootDirectory ${rootDirectory} does not exist`
+    )
+  }
+  if (!fs.statSync(rootDirectory).isDirectory()) {
+    throw new Error(
+      `The provided rootDirectory ${rootDirectory} is not a valid directory`
+    )
+  }
+  info(`Root directory input is valid!`)
+}
+
+/**
+ * Creates a specification that describes how a zip file will be created for a set of input files
+ * @param filesToZip a list of file that should be included in the zip
+ * @param rootDirectory an absolute root directory path common to all input files that that will be trimmed from the final zip structure
+ */
+export function getUploadZipSpecification(
+  filesToZip: string[],
+  rootDirectory: string
+): UploadZipSpecification[] {
+  const specification: UploadZipSpecification[] = []
+
+  // Normalize and resolve, this allows for either absolute or relative paths to be used
+  rootDirectory = normalize(rootDirectory)
+  rootDirectory = resolve(rootDirectory)
+
+  /*
+     Example
+     
+     Input:
+       rootDirectory: '/home/user/files/plz-upload'
+       artifactFiles: [
+         '/home/user/files/plz-upload/file1.txt',
+         '/home/user/files/plz-upload/file2.txt',
+         '/home/user/files/plz-upload/dir/file3.txt'
+       ]
+     
+     Output:
+       specifications: [
+         ['/home/user/files/plz-upload/file1.txt', '/file1.txt'],
+         ['/home/user/files/plz-upload/file1.txt', '/file2.txt'],
+         ['/home/user/files/plz-upload/file1.txt', '/dir/file3.txt']
+       ]
+
+      The final zip that is later uploaded will look like this:
+
+      my-artifact.zip
+        - file.txt
+        - file2.txt
+        - dir/
+          - file3.txt
+  */
+  for (let file of filesToZip) {
+    if (!fs.existsSync(file)) {
+      throw new Error(`File ${file} does not exist`)
+    }
+    if (!fs.statSync(file).isDirectory()) {
+      // Normalize and resolve, this allows for either absolute or relative paths to be used
+      file = normalize(file)
+      file = resolve(file)
+      if (!file.startsWith(rootDirectory)) {
+        throw new Error(
+          `The rootDirectory: ${rootDirectory} is not a parent directory of the file: ${file}`
+        )
+      }
+
+      // Check for forbidden characters in file paths that may cause ambiguous behavior if downloaded on different file systems
+      const uploadPath = file.replace(rootDirectory, '')
+      validateFilePath(uploadPath)
+
+      specification.push({
+        sourcePath: file,
+        destinationPath: uploadPath
+      })
+    } else {
+      // Empty directory
+      const directoryPath = file.replace(rootDirectory, '')
+      validateFilePath(directoryPath)
+
+      specification.push({
+        sourcePath: null,
+        destinationPath: directoryPath
+      })
+    }
+  }
+  return specification
+}