name: Comment with mypy_primer diff

on:
  workflow_run:
    workflows:
      - Run mypy_primer
    types:
      - completed

permissions:
  contents: read
  pull-requests: write

jobs:
  comment:
    name: Comment PR from mypy_primer
    runs-on: ubuntu-latest
    if: ${{ github.event.workflow_run.conclusion == 'success' }}
    steps:
      - name: Download diffs
        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3  # v9.0.0
        with:
          script: |
            const fs = require('fs');
            const artifacts = await github.rest.actions.listWorkflowRunArtifacts({
               owner: context.repo.owner,
               repo: context.repo.repo,
               run_id: ${{ github.event.workflow_run.id }},
            });
            const [matchArtifact] = artifacts.data.artifacts.filter((artifact) =>
              artifact.name == "mypy_primer_diffs");

            const download = await github.rest.actions.downloadArtifact({
               owner: context.repo.owner,
               repo: context.repo.repo,
               artifact_id: matchArtifact.id,
               archive_format: "zip",
            });
            fs.writeFileSync("diff.zip", Buffer.from(download.data));

      - run: unzip diff.zip

      - name: Get PR number
        id: get-pr-number
        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3  # v9.0.0
        with:
          script: |
            const fs = require('fs');
            return parseInt(fs.readFileSync("pr_number.txt", { encoding: "utf8" }))

      - name: Hide old comments
        uses: int128/hide-comment-action@392bc214093dafaebdf99c7d6298245262832d15  # v1.58.0
        with:
          token: ${{ secrets.GITHUB_TOKEN }}
          issue-number: ${{ steps.get-pr-number.outputs.result }}

      - run: cat diff_*.txt | tee fulldiff.txt

      - name: Post comment
        id: post-comment
        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3  # v9.0.0
        with:
          github-token: ${{ secrets.GITHUB_TOKEN }}
          script: |
            const MAX_CHARACTERS = 50000
            const MAX_CHARACTERS_PER_PROJECT = MAX_CHARACTERS / 3

            const fs = require('fs')
            let data = fs.readFileSync('fulldiff.txt', { encoding: 'utf8' })

            function truncateIfNeeded(original, maxLength) {
              if (original.length <= maxLength) {
                return original
              }
              let truncated = original.substring(0, maxLength)
              // further, remove last line that might be truncated
              truncated = truncated.substring(0, truncated.lastIndexOf('\n'))
              let lines_truncated = original.split('\n').length - truncated.split('\n').length
              return `${truncated}\n\n... (truncated ${lines_truncated} lines) ...`
            }

            const projects = data.split('\n\n')
            // don't let one project dominate
            data = projects.map(project => truncateIfNeeded(project, MAX_CHARACTERS_PER_PROJECT)).join('\n\n')
            // posting comment fails if too long, so truncate
            data = truncateIfNeeded(data, MAX_CHARACTERS)

            console.log("Diff from mypy_primer:")
            console.log(data)

            let body
            if (data.trim()) {
              body = 'Diff from [mypy_primer](https://github.com/hauntsaninja/mypy_primer), '
              body += 'showing the effect of this PR on type check results on a corpus of open source code:\n```diff\n'
              body += data + '```'
              const prNumber = parseInt(fs.readFileSync("pr_number.txt", { encoding: "utf8" }))
              await github.rest.issues.createComment({
                issue_number: prNumber,
                owner: context.repo.owner,
                repo: context.repo.repo,
                body
              })
            }
