#!/usr/bin/env bash

# Requests reviews for a PR after verifying that the base branch is correct

set -euo pipefail
tmp=$(mktemp -d)
trap 'rm -rf "$tmp"' exit
SCRIPT_DIR=$(dirname "$0")

log() {
    echo "$@" >&2
}

effect() {
    if [[ -n "${DRY_MODE:-}" ]]; then
        log "Skipping in dry mode:" "${@@Q}"
    else
        "$@"
    fi
}

if (( $# < 3 )); then
    log "Usage: $0 GITHUB_REPO PR_NUMBER OWNERS_FILE"
    exit 1
fi
baseRepo=$1
prNumber=$2
ownersFile=$3

log "Fetching PR info"
prInfo=$(gh api \
  -H "Accept: application/vnd.github+json" \
  -H "X-GitHub-Api-Version: 2022-11-28" \
  "/repos/$baseRepo/pulls/$prNumber")

baseBranch=$(jq -r .base.ref <<< "$prInfo")
log "Base branch: $baseBranch"
prRepo=$(jq -r .head.repo.full_name <<< "$prInfo")
log "PR repo: $prRepo"
prBranch=$(jq -r .head.ref <<< "$prInfo")
log "PR branch: $prBranch"
prAuthor=$(jq -r .user.login <<< "$prInfo")
log "PR author: $prAuthor"

extraArgs=()
if pwdRepo=$(git rev-parse --show-toplevel 2>/dev/null); then
    # Speedup for local runs
    extraArgs+=(--reference-if-able "$pwdRepo")
fi

log "Fetching Nixpkgs commit history"
# We only need the commit history, not the contents, so we can do a tree-less clone using tree:0
# https://github.blog/open-source/git/get-up-to-speed-with-partial-clone-and-shallow-clone/#user-content-quick-summary
git clone --bare --filter=tree:0 --no-tags --origin upstream "${extraArgs[@]}" https://github.com/"$baseRepo".git "$tmp"/nixpkgs.git

log "Fetching the PR commit history"
# Fetch the PR
git -C "$tmp/nixpkgs.git" remote add fork https://github.com/"$prRepo".git
# This remote config is the same as --filter=tree:0 when cloning
git -C "$tmp/nixpkgs.git" config remote.fork.partialclonefilter tree:0
git -C "$tmp/nixpkgs.git" config remote.fork.promisor true

# This should not conflict with any refs in Nixpkgs
headRef=refs/remotes/fork/pr
# Only fetch into a remote ref, because the local ref namespace is used by Nixpkgs, don't want any conflicts
git -C "$tmp/nixpkgs.git" fetch --no-tags fork "$prBranch":"$headRef"

log "Checking correctness of the base branch"
if ! "$SCRIPT_DIR"/verify-base-branch.sh "$tmp/nixpkgs.git" "$headRef" "$baseRepo" "$baseBranch" "$prRepo" "$prBranch" | tee "$tmp/invalid-base-error" >&2; then
    log "Posting error as comment"
    if ! response=$(effect gh api \
        --method POST \
        -H "Accept: application/vnd.github+json" \
        -H "X-GitHub-Api-Version: 2022-11-28" \
        "/repos/$baseRepo/issues/$prNumber/comments" \
        -F "body=@$tmp/invalid-base-error"); then
        log "Failed to post the comment: $response"
    fi
    exit 1
fi

log "Getting code owners to request reviews from"
"$SCRIPT_DIR"/get-reviewers.sh "$tmp/nixpkgs.git" "$baseBranch" "$headRef" "$ownersFile" "$prAuthor" > "$tmp/reviewers.json"

log "Requesting reviews from: $(<"$tmp/reviewers.json")"

if ! response=$(effect gh api \
    --method POST \
    -H "Accept: application/vnd.github+json" \
    -H "X-GitHub-Api-Version: 2022-11-28" \
    "/repos/$baseRepo/pulls/$prNumber/requested_reviewers" \
    --input "$tmp/reviewers.json"); then
    log "Failed to request reviews: $response"
    exit 1
fi

log "Successfully requested reviews"