Write job summary in post action

- Save build results in file encoded as JSON
- Read all build results in post action and render as table in job summary

src/job-summary.ts

@@ -0,0 +1,59 @@
+import * as core from '@actions/core'
+import fs from 'fs'
+import path from 'path'
+
+interface BuildResult {
+    get rootProject(): string
+    get requestedTasks(): string
+    get gradleVersion(): string
+    get buildFailed(): boolean
+    get buildScanUri(): string
+}
+
+export function writeJobSummary(): void {
+    const buildResults = loadBuildResults()
+    if (buildResults.length === 0) {
+        core.debug('No Gradle build results found. Summary table will not be generated.')
+    } else {
+        writeSummaryTable(buildResults)
+    }
+}
+
+function loadBuildResults(): BuildResult[] {
+    const buildResultsDir = path.resolve(process.env['RUNNER_TEMP']!, '.build-results')
+    if (!fs.existsSync(buildResultsDir)) {
+        return []
+    }
+
+    return fs.readdirSync(buildResultsDir).map(file => {
+        // Every file in the .build-results dir should be a BuildResults JSON
+        const filePath = path.join(buildResultsDir, file)
+        const content = fs.readFileSync(filePath, 'utf8')
+        return JSON.parse(content) as BuildResult
+    })
+}
+
+function writeSummaryTable(results: BuildResult[]): void {
+    core.summary.addRaw(`| Root Project | Tasks | Gradle Version | Outcome |\n| - | - | - | - |\n`)
+    for (const result of results) {
+        const tableRow = `| ${result.rootProject} \
+                          | ${result.requestedTasks} \
+                          | ${result.gradleVersion} \
+                          | ${renderOutcome(result)} \
+                          |\n`
+        core.summary.addRaw(tableRow)
+    }
+    core.summary.write()
+}
+
+function renderOutcome(result: BuildResult): string {
+    if (result.buildScanUri) {
+        return `[![Gradle Build](https://img.shields.io/badge/Build%20Scan%E2%84%A2-${
+            result.buildFailed ? 'FAILED-red' : 'SUCCESS-brightgreen'
+        }?logo=Gradle)](${result.buildScanUri})`
+    }
+
+    return `![Gradle Build](https://img.shields.io/badge/${
+        result.buildFailed ? 'FAILED-red' : 'SUCCESS-brightgreen'
+    }?logo=Gradle)`
+}