First version

github-game-of-life.js

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+// GitHub Game of Life - 1.0.1
+// Chris Johnson
+// @defaced / defaced.dev / github.com/workeffortwaste
+(function () {
+  const startGgol = () => {
+    // Settings
+    const cols = 53
+    const rows = 7
+
+    // Pull down the contributions from the graph.
+    const contributions = document.getElementsByClassName('js-calendar-graph-svg')[0].children[0].getElementsByTagName('g')
+
+    // Read contributions as columns from the contribution frame.
+    const readContributions = (contributions) => {
+      // Init output Arr.
+      const output = []
+
+      for (const contribution of contributions) {
+        const days = contribution.getElementsByTagName('rect')
+        const lifeRow = []
+        for (const day of days) {
+          // Convert to live or dead cells.
+          lifeRow.push(day.getAttribute('data-count') > 0 ? 1 : 0)
+        }
+        // Add column to output.
+        output.push(lifeRow)
+      }
+
+      // Fill in any blanks in the first and last rows.
+      for (let i = 0; i < 7; i++) {
+        if (!output[0][i]) {
+          output[0][i] = 0
+        }
+        if (!output[output.length - 1][i]) {
+          output[output.length - 1][i] = 0
+        }
+      }
+
+      return output
+    }
+
+    // Our initial game of life state.
+    let lifeArray = readContributions(contributions)
+
+    // Write to the contributions graphic.
+    const writeContributions = (contributions, nextGenerationArray) => {
+      for (let i = 0; i < contributions.length; i++) {
+        const days = contributions[i].getElementsByTagName('rect')
+        for (let d = 0; d < 7; d++) { // Magic number - 7 days of the week.
+          try { days[d].setAttribute('fill', nextGenerationArray[i][d] ? '#40c463' : '#ebedf0') } catch {}
+        }
+      }
+    }
+
+    const countNeighbors = (grid, x, y) => {
+      let sum = 0
+
+      for (let i = -1; i < 2; i++) {
+        for (let j = -1; j < 2; j++) {
+          const col = (x + i + cols) % cols
+          const row = (y + j + rows) % rows
+          sum += grid[col][row]
+        }
+      }
+
+      sum -= grid[x][y]
+      return sum
+    }
+
+    const generateNextIteration = (grid) => {
+      // Make empty array
+      const next = [...Array(53)].map(e => Array(7))
+
+      for (let i = 0; i < cols; i++) {
+        for (let j = 0; j < rows; j++) {
+          const state = grid[i][j]
+          const neighbors = countNeighbors(grid, i, j)
+
+          if (state === 0 && neighbors === 3) {
+            next[i][j] = 1
+          } else if (state === 1 && (neighbors < 2 || neighbors > 3)) {
+            next[i][j] = 0
+          } else {
+            next[i][j] = state
+          }
+        }
+      }
+
+      return next
+    }
+
+    const update = () => {
+      // Generate the next iteration.
+      const next = generateNextIteration(lifeArray)
+
+      // If the output is the same as the input we've reached a stable state so kill the interval.
+      if (JSON.stringify(next) === JSON.stringify(lifeArray)) {
+        clearInterval(timer)
+      }
+
+      // Update the lifeArray with the next generation.
+      lifeArray = next
+      writeContributions(contributions, lifeArray)
+    }
+
+    // Update every 500 ms.
+    const timer = setInterval(function () { update() }, 500)
+  }
+
+  const observerGgol = (entry) => {
+    if (entry[0].intersectionRatio > 0) {
+      // Kill the observer.
+      observer.disconnect()
+      // Start the game of life.
+      startGgol()
+    }
+  }
+
+  const observer = new IntersectionObserver(observerGgol)
+  try { observer.observe(document.getElementsByClassName('js-calendar-graph-svg')[0]) } catch {}
+})()

manifest.json

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+{
+  "name": "GitHub Game of Life",
+  "description": "Replace the GitHub contributions graph with Conway's Game of Life.",
+  "version": "1.0.1",
+  "icons": {
+    "16": "icon16.png",
+    "48": "icon48.png",
+    "128": "icon128.png"
+  },
+  "content_scripts": [
+    {
+      "matches": [
+        "https://github.com/*"
+      ],
+      "exclude_globs": ["https://github.com/*/*"],
+      "js": ["github-game-of-life.js"],
+      "run_at": "document_end"
+    }
+  ],
+  "manifest_version": 2
+}