1 files changed, 102 insertions, 0 deletions
diff --git a/src/misc/generate-docs.ts b/src/misc/generate-docs.ts
new file mode 100644
index 0000000..c882c55
--- /dev/null
+++ b/src/misc/generate-docs.ts
@@ -0,0 +1,102 @@
+import * as fs from 'fs'
+import * as os from 'os'
+import * as path from 'path'
+import * as yaml from 'js-yaml'
+
+//
+// SUMMARY
+//
+// This script rebuilds the usage section in the README.md to be consistent with the action.yml
+
+function updateUsage(
+  actionReference: string,
+  actionYamlPath: string = 'action.yml',
+  readmePath: string = 'README.md',
+  startToken: string = '<!-- start usage -->',
+  endToken: string = '<!-- end usage -->'
+): void {
+  if (!actionReference) {
+    throw new Error('Parameter actionReference must not be empty')
+  }
+
+  // Load the action.yml
+  const actionYaml = yaml.safeLoad(fs.readFileSync(actionYamlPath).toString())
+
+  // Load the README
+  const originalReadme = fs.readFileSync(readmePath).toString()
+
+  // Find the start token
+  const startTokenIndex = originalReadme.indexOf(startToken)
+  if (startTokenIndex < 0) {
+    throw new Error(`Start token '${startToken}' not found`)
+  }
+
+  // Find the end token
+  const endTokenIndex = originalReadme.indexOf(endToken)
+  if (endTokenIndex < 0) {
+    throw new Error(`End token '${endToken}' not found`)
+  } else if (endTokenIndex < startTokenIndex) {
+    throw new Error('Start token must appear before end token')
+  }
+
+  // Build the new README
+  const newReadme: string[] = []
+
+  // Append the beginning
+  newReadme.push(originalReadme.substr(0, startTokenIndex + startToken.length))
+
+  // Build the new usage section
+  newReadme.push('```yaml', `- uses: ${actionReference}`, '  with:')
+  const inputs = actionYaml.inputs
+  let firstInput = true
+  for (const key of Object.keys(inputs)) {
+    const input = inputs[key]
+
+    // Line break between inputs
+    if (!firstInput) {
+      newReadme.push('')
+    }
+
+    // Constrain the width of the description
+    const width = 80
+    let description = input.description as string
+    while (description) {
+      // Longer than width? Find a space to break apart
+      let segment: string = description
+      if (description.length > width) {
+        segment = description.substr(0, width + 1)
+        while (!segment.endsWith(' ')) {
+          segment = segment.substr(0, segment.length - 1)
+        }
+      } else {
+        segment = description
+      }
+
+      description = description.substr(segment.length) // Remaining
+      segment = segment.trimRight() // Trim the trailing space
+      newReadme.push(`    # ${segment}`)
+    }
+
+    // Input and default
+    if (input.default !== undefined) {
+      newReadme.push(`    # Default: ${input.default}`)
+    }
+    newReadme.push(`    ${key}: ''`)
+
+    firstInput = false
+  }
+
+  newReadme.push('```')
+
+  // Append the end
+  newReadme.push(originalReadme.substr(endTokenIndex))
+
+  // Write the new README
+  fs.writeFileSync(readmePath, newReadme.join(os.EOL))
+}
+
+updateUsage(
+  'actions/checkout@preview',
+  path.join(__dirname, '..', '..', 'action.yml'),
+  path.join(__dirname, '..', '..', 'README.md')
+)