function requireEnv(key: string): string {
  const value = process.env[key];
  if (!value) throw new Error(`Missing required env var: ${key}`);
  return value;
}

const config = {
  githubApiKey: requireEnv("GH_API_KEY"),
  forgejoApiKey: requireEnv("FJ_API_KEY"),
  forgejoUsername: requireEnv("FJ_USER"),
  forgejoURL: requireEnv("FJ_URL"),
};

const now = new Date();
const oneYearAgo = new Date();
oneYearAgo.setFullYear(oneYearAgo.getFullYear() - 1);
const formattedOneYearAgo = oneYearAgo.toISOString().replace("Z", "+00:00");

function buildGhQuery(from: string, to: string): string {
  return `{
    viewer {
      contributionsCollection(from: "${from}", to: "${to}") {
        contributionCalendar {
          weeks {
            contributionDays {
              date
              contributionCount
            }
          }
        }
        commitContributionsByRepository(maxRepositories: 100) {
          repository {
            nameWithOwner
            isMirror
          }
          contributions(first: 100) {
            nodes {
              occurredAt
              commitCount
            }
          }
        }
      }
    }
  }`;
}

type DayContributions = {
  [repo: string]: number;
};

type ActivityMap = {
  [day: string]: DayContributions;
};

function mergeInto(target: ActivityMap, source: ActivityMap): void {
  for (const [day, repos] of Object.entries(source)) {
    if (!target[day]) target[day] = {};
    for (const [repo, count] of Object.entries(repos)) {
      target[day]![repo] = (target[day]![repo] ?? 0) + count;
    }
  }
}

function repoBaseName(fullName: string): string {
  return fullName.split("/")[1]?.toLowerCase() ?? fullName.toLowerCase();
}

function deduplicateAcrossPlatforms(
  ghMap: ActivityMap,
  fjMap: ActivityMap,
): ActivityMap {
  const ghBaseNames = new Set<string>();
  for (const repos of Object.values(ghMap)) {
    for (const repo of Object.keys(repos)) {
      if (repo !== "private") ghBaseNames.add(repoBaseName(repo));
    }
  }

  const sharedBaseNames = new Set<string>();
  for (const repos of Object.values(fjMap)) {
    for (const repo of Object.keys(repos)) {
      if (repo !== "private" && ghBaseNames.has(repoBaseName(repo))) {
        sharedBaseNames.add(repoBaseName(repo));
      }
    }
  }

  const result: ActivityMap = {};
  const allDays = new Set([...Object.keys(ghMap), ...Object.keys(fjMap)]);

  for (const day of allDays) {
    result[day] = {};
    const ghDay = ghMap[day] ?? {};
    const fjDay = fjMap[day] ?? {};

    for (const [repo, count] of Object.entries(ghDay)) {
      const base = repoBaseName(repo);
      if (repo !== "private" && sharedBaseNames.has(base)) {
        const fjRepo = Object.keys(fjDay).find((r) => repoBaseName(r) === base);
        const fjCount = fjRepo ? (fjDay[fjRepo] ?? 0) : 0;
        if (count >= fjCount) {
          result[day]![repo] = count;
        }
        // else: Forgejo wins, added below
      } else {
        result[day]![repo] = (result[day]![repo] ?? 0) + count;
      }
    }

    for (const [repo, count] of Object.entries(fjDay)) {
      const base = repoBaseName(repo);
      if (repo !== "private" && sharedBaseNames.has(base)) {
        const ghRepo = Object.keys(ghDay).find((r) => repoBaseName(r) === base);
        const ghCount = ghRepo ? (ghDay[ghRepo] ?? 0) : 0;
        if (count > ghCount) {
          if (ghRepo) delete result[day]![ghRepo];
          result[day]![repo] = count;
        }
        // else: GitHub already won
      } else {
        result[day]![repo] = (result[day]![repo] ?? 0) + count;
      }
    }

    if (Object.keys(result[day]!).length === 0) {
      delete result[day];
    }
  }

  return result;
}

function parseGitHubContributions(data: any): ActivityMap {
  const result: ActivityMap = {};

  const collection = data?.data?.viewer?.contributionsCollection;

  const calendarMap: { [day: string]: number } = {};
  for (const week of collection?.contributionCalendar?.weeks ?? []) {
    for (const day of week.contributionDays) {
      if (day.contributionCount > 0) calendarMap[day.date] = day.contributionCount;
    }
  }

  for (const repoEntry of collection?.commitContributionsByRepository ?? []) {
    const repoName: string = repoEntry.repository.nameWithOwner;
    if (repoEntry.repository.isMirror) continue;

    for (const contribution of repoEntry.contributions.nodes) {
      const day: string = contribution.occurredAt.split("T")[0];
      const count: number = contribution.commitCount;
      if (!result[day]) result[day] = {};
      result[day]![repoName] = (result[day]![repoName] ?? 0) + count;
    }
  }

  for (const [day, total] of Object.entries(calendarMap)) {
    const known = Object.values(result[day] ?? {}).reduce((a, b) => a + b, 0);
    const hidden = total - known;
    if (hidden > 0) {
      if (!result[day]) result[day] = {};
      result[day]!["private"] = (result[day]!["private"] ?? 0) + hidden;
    }
  }

  return result;
}

function parseForgejoActivity(activities: any[]): ActivityMap {
  const result: ActivityMap = {};

  for (const activity of activities) {
    if (activity.repo?.mirror) continue;
    if (activity.op_type !== "commit_repo") continue;

    const isPrivate: boolean = activity.repo?.private ?? false;
    const repoFullName: string = activity.repo?.full_name ?? "unknown";
    const displayName = isPrivate ? "private" : repoFullName;

    let content: { Commits?: { Timestamp: string | number }[] };
    try {
      content = JSON.parse(activity.content);
    } catch {
      continue;
    }

    for (const commit of content.Commits ?? []) {
      let day: string;
      if (typeof commit.Timestamp === "number") {
        day = new Date(commit.Timestamp * 1000).toISOString().split("T")[0]!;
      } else {
        day = commit.Timestamp.split("T")[0]!;
      }

      if (!result[day]) result[day] = {};
      result[day]![displayName] = (result[day]![displayName] ?? 0) + 1;
    }
  }

  return result;
}

async function getForgejoActivityMap(): Promise<ActivityMap> {
  const pageLimit = 50;
  let page = 1;
  const map: ActivityMap = {};

  while (true) {
    const response = await fetch(
      `${config.forgejoURL}/api/v1/users/${config.forgejoUsername}/activities/feeds?limit=${pageLimit}&page=${page}&after=${formattedOneYearAgo}`,
      { headers: { Authorization: `Bearer ${config.forgejoApiKey}` } },
    );

    if (!response.ok) {
      throw new Error(
        `Forgejo API error: ${response.status} ${response.statusText}`,
      );
    }

    const activities: any[] = await response.json();
    if (activities.length === 0) break;

    const pageMap = parseForgejoActivity(activities);
    mergeInto(map, pageMap);

    if (activities.length < pageLimit) break;
    page++;
  }

  return map;
}

async function ghFetch(query: string): Promise<any> {
  const response = await fetch("https://api.github.com/graphql", {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      Authorization: `Bearer ${config.githubApiKey}`,
    },
    body: JSON.stringify({ query }),
  });
  if (!response.ok) {
    throw new Error(
      `GitHub API error: ${response.status} ${response.statusText}`,
    );
  }
  return response.json();
}

async function getGitHubActivityMap(): Promise<ActivityMap> {
  const ranges = Array.from({ length: 12 }, (_, i) => {
    const to = new Date(now);
    to.setMonth(to.getMonth() - i);
    const from = new Date(to);
    from.setMonth(from.getMonth() - 1);
    return { from: from.toISOString(), to: to.toISOString() };
  });

  const results = await Promise.all(
    ranges.map(({ from, to }) => ghFetch(buildGhQuery(from, to))),
  );

  const map: ActivityMap = {};
  for (const data of results) {
    mergeInto(map, parseGitHubContributions(data));
  }

  return map;
}

async function makeActivityMap(): Promise<ActivityMap> {
  const [ghMap, fjMap] = await Promise.all([
    getGitHubActivityMap(),
    getForgejoActivityMap(),
  ]);

  return deduplicateAcrossPlatforms(ghMap, fjMap);
}

const activityMap = await makeActivityMap();
await Bun.write(
  "../static/activity.json",
  JSON.stringify(activityMap, null, 2),
);
console.log(
  `Wrote ${Object.keys(activityMap).length} days of activity to out/activity.json`,
);