From 7fffb151c57d5a1feebac8f09ac56afcb6d84e34 Mon Sep 17 00:00:00 2001
From: Simon Lecoq <22963968+lowlighter@users.noreply.github.com>
Date: Tue, 26 Oct 2021 00:11:06 -0400
Subject: [PATCH] feat(core): add output_condition option  (#620) [skip ci]

---
 source/app/action/index.mjs      | 25 ++++++++++++++++++++++++-
 source/app/metrics/utils.mjs     | 24 ++++++++++++++++++++++++
 source/plugins/core/README.md    |  4 ++++
 source/plugins/core/metadata.yml |  9 +++++++++
 4 files changed, 61 insertions(+), 1 deletion(-)

diff --git a/source/app/action/index.mjs b/source/app/action/index.mjs
index 1dd59940..aeaca919 100644
--- a/source/app/action/index.mjs
+++ b/source/app/action/index.mjs
@@ -93,6 +93,7 @@ async function wait(seconds) {
       retries,
       "retries.delay":retries_delay,
       "output.action":_action,
+      "output.condition":_output_condition,
       delay,
       ...config
     } = metadata.plugins.core.inputs.action({core})
@@ -321,9 +322,31 @@ async function wait(seconds) {
       throw error ?? new Error("Could not render metrics")
     info("Status", "complete")
 
-    //Save output to renders output folder
+    //Output condition
     info.break()
     info.section("Saving")
+    info("Output condition", _output_condition)
+    if ((_output_condition === "skip-if-only-metadata-changed")&&((committer.commit) || (committer.pr))) {
+      const {svg} = await import("../metrics/utils.mjs")
+      let data = ""
+      try {
+        data = `${Buffer.from((await committer.rest.repos.getContent({...github.context.repo, ref:`heads/${committer.head}`, path:filename})).data.content, "base64")}`
+      }
+      catch (error) {
+        if (error.response.status !== 404)
+          throw error
+      }
+      const previous = await svg.hash(data)
+      info("Previous hash", previous)
+      const current = await svg.hash(rendered)
+      info("Current hash", current)
+      const changed = (previous !== current)
+      info("Content changed", changed)
+      if (!changed)
+        committer.commit = false
+    }
+
+    //Save output to renders output folder
     if (dryrun)
       info("Actions to perform", "(none)")
     else {
diff --git a/source/app/metrics/utils.mjs b/source/app/metrics/utils.mjs
index c5c7f873..86969818 100644
--- a/source/app/metrics/utils.mjs
+++ b/source/app/metrics/utils.mjs
@@ -24,6 +24,7 @@ import fetch from "node-fetch"
 import readline from "readline"
 import emoji from "emoji-name-map"
 import minimatch from "minimatch"
+import crypto from "crypto"
 prism_lang()
 
 //Exports
@@ -413,6 +414,29 @@ export const svg = {
     console.debug("metrics/svg/resize > rendering complete")
     return {resized, mime}
   },
+  /**Hash a SVG (removing its metadata first)*/
+  async hash(rendered) {
+    //Handle empty case
+    if (!rendered)
+      return null
+    //Instantiate browser if needed
+    if (!svg.resize.browser) {
+      svg.resize.browser = await puppeteer.launch()
+      console.debug(`metrics/svg/hash > started ${await svg.resize.browser.version()}`)
+    }
+    //Compute hash
+    const page = await svg.resize.browser.newPage()
+    await page.setContent(rendered, {waitUntil:["load", "domcontentloaded", "networkidle2"]})
+    const data = await page.evaluate(async () => {
+      document.querySelector("footer")?.remove()
+      return document.querySelector("svg").outerHTML
+    })
+    const hash = crypto.createHash("md5").update(data).digest("hex")
+    //Result
+    await page.close()
+    console.debug(`metrics/svg/hash > MD5=${hash}`)
+    return hash
+  },
   /**Render twemojis */
   async twemojis(rendered, {custom = true} = {}) {
     //Load emojis
diff --git a/source/plugins/core/README.md b/source/plugins/core/README.md
index b8b189c4..540875e3 100644
--- a/source/plugins/core/README.md
+++ b/source/plugins/core/README.md
@@ -203,6 +203,10 @@ It is possible to configure output behaviour using `output_action` option, which
 - `gist`, where output will be stored an already existing gist
   - To use this feature, a `gists` scope must be granted to your `token` and `committer_gist` identifier must be provided
 
+It also possible to alter output condition using `output_action` option, which can be set to:
+- `always`, to always push changes (provided that git sha changed)
+- `skip-if-only-metadata-changed`, to skip changes if only metadata contained in footer changed
+
 #### ℹ️ Examples workflows
 
 ```yaml
diff --git a/source/plugins/core/metadata.yml b/source/plugins/core/metadata.yml
index 33ce4854..c896d716 100644
--- a/source/plugins/core/metadata.yml
+++ b/source/plugins/core/metadata.yml
@@ -94,6 +94,15 @@ inputs:
       - pull-request-rebase # Same as "pull-request" and additionaly rebase and merge pull request
       - gist                # Save output to "committer_gist"
 
+  # Output condition
+  output_condition:
+    description: Output condition
+    type: string
+    default: always
+    values:
+      - always                        # Always push changes
+      - skip-if-only-metadata-changed # Skip changes if only metadata contained in footer changed
+
   # Optimize SVG image to reduce its filesize
   # Some templates may not support this option
   optimize: