restore ArchiveUtils for import scripts (#2314)

import/asana/importAsana.ts

@@ -3,7 +3,7 @@
 import * as fs from 'fs'
 import minimist from 'minimist'
 import {exit} from 'process'
-import {ArchiveUtils} from '../../webapp/src/blocks/archive'
+import {ArchiveUtils} from '../util/archive'
 import {Block} from '../../webapp/src/blocks/block'
 import {IPropertyOption, IPropertyTemplate, createBoard} from '../../webapp/src/blocks/board'
 import {createBoardView} from '../../webapp/src/blocks/boardView'

import/jira/jiraImporter.ts

@@ -2,7 +2,7 @@
 // See LICENSE.txt for license information.
 import * as fs from 'fs'
 import {exit} from 'process'
-import {ArchiveUtils} from '../../webapp/src/blocks/archive'
+import {ArchiveUtils} from '../util/archive'
 import {Block} from '../../webapp/src/blocks/block'
 import {IPropertyOption, IPropertyTemplate, createBoard} from '../../webapp/src/blocks/board'
 import {createBoardView} from '../../webapp/src/blocks/boardView'

import/notion/importNotion.ts

@@ -3,7 +3,7 @@ import * as fs from 'fs'
 import minimist from 'minimist'
 import path from 'path'
 import {exit} from 'process'
-import {ArchiveUtils} from '../../webapp/src/blocks/archive'
+import {ArchiveUtils} from '../util/archive'
 import {Block} from '../../webapp/src/blocks/block'
 import {IPropertyTemplate, createBoard} from '../../webapp/src/blocks/board'
 import {createBoardView} from '../../webapp/src/blocks/boardView'

import/todoist/importTodoist.ts

@@ -3,7 +3,7 @@
 import * as fs from 'fs'
 import minimist from 'minimist'
 import {exit} from 'process'
-import {ArchiveUtils} from '../../webapp/src/blocks/archive'
+import {ArchiveUtils} from '../util/archive'
 import {Block} from '../../webapp/src/blocks/block'
 import {IPropertyOption, IPropertyTemplate, createBoard} from '../../webapp/src/blocks/board'
 import {createBoardView} from '../../webapp/src/blocks/boardView'

import/trello/importTrello.ts

@@ -3,7 +3,7 @@
 import * as fs from 'fs'
 import minimist from 'minimist'
 import {exit} from 'process'
-import {ArchiveUtils} from '../../webapp/src/blocks/archive'
+import {ArchiveUtils} from '../util/archive'
 import {Block} from '../../webapp/src/blocks/block'
 import {IPropertyOption, IPropertyTemplate, createBoard} from '../../webapp/src/blocks/board'
 import {createBoardView} from '../../webapp/src/blocks/boardView'

import/util/archive.ts

@@ -0,0 +1,81 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+import {Block} from '../../webapp/src/blocks/block'
+
+interface ArchiveHeader {
+    version: number
+    date: number
+}
+
+interface ArchiveLine {
+    type: string,
+    data: unknown,
+}
+
+// This schema allows the expansion of additional line types in the future
+interface BlockArchiveLine extends ArchiveLine {
+    type: 'block',
+    data: Block
+}
+
+class ArchiveUtils {
+    static buildBlockArchive(blocks: readonly Block[]): string {
+        const header: ArchiveHeader = {
+            version: 1,
+            date: Date.now(),
+        }
+
+        const headerString = JSON.stringify(header)
+        let content = headerString + '\n'
+        for (const block of blocks) {
+            const line: BlockArchiveLine = {
+                type: 'block',
+                data: block,
+            }
+            const lineString = JSON.stringify(line)
+            content += lineString
+            content += '\n'
+        }
+
+        return content
+    }
+
+    static parseBlockArchive(contents: string): Block[] {
+        const blocks: Block[] = []
+        const allLineStrings = contents.split('\n')
+        if (allLineStrings.length >= 2) {
+            const headerString = allLineStrings[0]
+            const header = JSON.parse(headerString) as ArchiveHeader
+            if (header.date && header.version >= 1) {
+                const lineStrings = allLineStrings.slice(1)
+                let lineNum = 2
+                for (const lineString of lineStrings) {
+                    if (!lineString) {
+                        // Ignore empty lines, e.g. last line
+                        continue
+                    }
+                    const line = JSON.parse(lineString) as ArchiveLine
+                    if (!line || !line.type || !line.data) {
+                        throw new Error(`ERROR parsing line ${lineNum}`)
+                    }
+                    switch (line.type) {
+                    case 'block': {
+                        const blockLine = line as BlockArchiveLine
+                        const block = blockLine.data
+                        blocks.push(block)
+                        break
+                    }
+                    }
+
+                    lineNum += 1
+                }
+            } else {
+                throw new Error('ERROR parsing header')
+            }
+        }
+
+        return blocks
+    }
+}
+
+export {ArchiveHeader, ArchiveLine, BlockArchiveLine, ArchiveUtils}