import { execFileSync } from "node:child_process";
import { resolve } from "node:path";
import type { LibSQLDatabase } from "drizzle-orm/libsql";
import { snapshots } from "./schema.ts";

const GIT_TIMEOUT_MS = 15_000;

function workspaceRoot(): string {
  const raw = process.env.GIT_WORKSPACE_ROOT;
  return raw ? resolve(raw) : resolve(process.cwd());
}

function gitErrorMessage(err: unknown): string {
  if (err instanceof Error) {
    const m = err.message.trim();
    return m.length > 200 ? `${m.slice(0, 197)}...` : m;
  }
  return String(err);
}

function runGit(cwd: string, args: string[]): string {
  return execFileSync("git", args, {
    cwd,
    encoding: "utf8",
    timeout: GIT_TIMEOUT_MS,
    maxBuffer: 2 * 1024 * 1024,
  }).trimEnd();
}

function countPorcelainLines(output: string): number {
  if (!output) return 0;
  return output.split("\n").filter((line) => line.length > 0).length;
}

export async function compute(db: LibSQLDatabase, _peers: unknown) {
  const root = workspaceRoot();
  const ts = Date.now();

  let branch = "";
  let headShort = "";
  let porcelainLines = 0;
  let hasUpstream = 0;
  let aheadCount = 0;
  let behindCount = 0;
  let gitError = "";

  try {
    const inside = runGit(root, ["rev-parse", "--is-inside-work-tree"]).trim();
    if (inside !== "true") {
      gitError = "not a git work tree";
      await db.insert(snapshots).values({
        ts,
        branch,
        headShort,
        porcelainLines,
        hasUpstream,
        aheadCount,
        behindCount,
        gitError,
      });
      return {
        workspaceRoot: root,
        branch,
        headShort,
        porcelainLines,
        hasUpstream: false,
        aheadCount,
        behindCount,
        gitError,
      };
    }

    branch = runGit(root, ["rev-parse", "--abbrev-ref", "HEAD"]);
    headShort = runGit(root, ["rev-parse", "--short", "HEAD"]);
    porcelainLines = countPorcelainLines(runGit(root, ["status", "--porcelain"]));

    try {
      runGit(root, ["rev-parse", "--abbrev-ref", "@{upstream}"]);
      hasUpstream = 1;
      const lb = runGit(root, ["rev-list", "--left-right", "--count", "HEAD...@{upstream}"]);
      const parts = lb.split(/[\t\s]+/).filter(Boolean);
      if (parts.length >= 2) {
        aheadCount = Number.parseInt(parts[0], 10) || 0;
        behindCount = Number.parseInt(parts[1], 10) || 0;
      }
    } catch {
      hasUpstream = 0;
      aheadCount = 0;
      behindCount = 0;
    }
  } catch (e) {
    gitError = gitErrorMessage(e);
  }

  await db.insert(snapshots).values({
    ts,
    branch,
    headShort,
    porcelainLines,
    hasUpstream,
    aheadCount,
    behindCount,
    gitError,
  });

  return {
    workspaceRoot: root,
    branch,
    headShort,
    porcelainLines,
    hasUpstream: hasUpstream === 1,
    aheadCount,
    behindCount,
    gitError: gitError || undefined,
  };
}