#!/usr/bin/env bun
/**
 * sl0ppi entry point.
 *
 * FAIL OPEN. If anything here goes wrong — bad layout, unreadable root,
 * unexpected state, a bug — warn on stderr and hand over to plain sl0ppij with
 * the user's arguments. When your environment breaks, the terminal is the thing
 * you debug it with; an orchestrator must never stand between you and it.
 */

import { spawnSync } from "node:child_process";
import { UserError } from "./core/errors.ts";
import { formatCheck, gather, report, worstLevel } from "./commands/doctor.ts";
import { init, initMessage } from "./commands/init.ts";
import { close, ls, open, print, up, type Context } from "./commands/workspace.ts";
import { loadRegistry, resolveRoot } from "./core/root.ts";
import { DEFAULT_BIN, insideSession, Sl0ppij } from "./core/sl0ppij.ts";

const USAGE = `sl0ppi — orchestrates sl0ppij sessions (one root = one session, one project = one tab)

usage:
  sl0ppi [up]            create/attach the root session, one tab per project
  sl0ppi ls              list projects and their tabs
  sl0ppi open <project>  ensure and focus a project's tab
  sl0ppi close <project> close a project's tab
  sl0ppi init [dir]      make a directory a project (writes .sl0ppi/layout.kdl)
  sl0ppi print <project> show the layout sl0ppi would use for a project
  sl0ppi doctor          check the installation
  sl0ppi help

options:
  --root DIR   treat DIR as the root (default: cwd, or the parent of a project)
  --depth N    how deep to scan for .sl0ppi markers (default: 1)
  --force      with init, overwrite an existing layout
  --fresh      with up, discard a dead session instead of resurrecting it
  -n, --dry-run
`;

interface Args {
  command: string;
  rest: string[];
  rootFlag?: string;
  depth: number;
  dryRun: boolean;
  force: boolean;
  fresh: boolean;
}

export function parseArgs(argv: string[]): Args {
  const rest: string[] = [];
  let rootFlag: string | undefined;
  let depth = 1;
  let dryRun = false;
  let force = false;
  let fresh = false;

  for (let i = 0; i < argv.length; i++) {
    const arg = argv[i] as string;
    if (arg === "--root") rootFlag = argv[++i];
    else if (arg.startsWith("--root=")) rootFlag = arg.slice("--root=".length);
    else if (arg === "--depth") depth = Number.parseInt(argv[++i] ?? "1", 10);
    else if (arg.startsWith("--depth=")) depth = Number.parseInt(arg.slice("--depth=".length), 10);
    else if (arg === "-n" || arg === "--dry-run") dryRun = true;
    else if (arg === "--force") force = true;
    else if (arg === "--fresh") fresh = true;
    else rest.push(arg);
  }

  const command = rest.length > 0 && KNOWN_VERBS.has(rest[0] as string) ? (rest.shift() as string) : "up";
  return {
    command,
    rest,
    rootFlag,
    depth: Number.isFinite(depth) ? depth : 1,
    dryRun,
    force,
    fresh,
  };
}

/**
 * Hand over to sl0ppij, replacing this process's role entirely.
 *
 * sl0ppi's own verbs and flags are stripped first: passing `up` to sl0ppij just
 * produces "unrecognized subcommand" and still leaves the user without a
 * terminal, which defeats the whole point of failing open. What survives is
 * anything sl0ppij would itself understand; if nothing does, a bare sl0ppij
 * gets you a session.
 */
const KNOWN_VERBS = new Set([
  "up",
  "ls",
  "open",
  "close",
  "init",
  "print",
  "doctor",
  "help",
]);
const OUR_VERBS = KNOWN_VERBS;
const OUR_FLAGS = new Set(["--root", "--depth", "-n", "--dry-run", "--force", "--fresh"]);

export function passthroughArgs(argv: string[]): string[] {
  const out: string[] = [];
  for (let i = 0; i < argv.length; i++) {
    const arg = argv[i] as string;
    if (OUR_FLAGS.has(arg)) {
      if (arg === "--root" || arg === "--depth") i++; // also drop its value
      continue;
    }
    if (arg.startsWith("--root=") || arg.startsWith("--depth=")) continue;
    if (out.length === 0 && OUR_VERBS.has(arg)) continue; // only the leading verb
    out.push(arg);
  }
  return out;
}

function fallThrough(argv: string[], why?: string): never {
  if (why) process.stderr.write(`sl0ppi: ${why}\n`);
  const passthrough = passthroughArgs(argv);

  // Falling open means "you still get your terminal", which only makes sense at
  // a terminal. Without a tty, a bare sl0ppij would silently CREATE a session
  // (that is how a handful of randomly-named junk sessions appeared during
  // testing), so report and exit instead.
  if (passthrough.length === 0 && (!process.stdin.isTTY || !process.stdout.isTTY)) {
    process.stderr.write("sl0ppi: not a tty; not starting sl0ppij\n");
    process.exit(1);
  }

  process.stderr.write("sl0ppi: falling through to sl0ppij\n");
  const bin = process.env.SL0PPI_BIN ?? DEFAULT_BIN;
  const proc = spawnSync(bin, passthrough, { stdio: "inherit" });
  process.exit(proc.status ?? 1);
}

export function main(argv: string[] = process.argv.slice(2)): void {
  let args: Args;
  try {
    args = parseArgs(argv);
  } catch (error) {
    fallThrough(argv, String(error));
  }

  if (args.command === "help" || argv.includes("-h") || argv.includes("--help")) {
    process.stdout.write(USAGE);
    return;
  }

  const client = new Sl0ppij();
  const sessionEnv = insideSession();

  let ctx: Context;
  try {
    ctx = {
      resolved: resolveRoot({
        rootFlag: args.rootFlag,
        cwd: process.cwd(),
        sessionEnv,
        registry: loadRegistry(),
      }),
      client,
      depth: args.depth,
      dryRun: args.dryRun,
      fresh: args.fresh,
      log: (message) => process.stdout.write(`${message}\n`),
    };
  } catch (error) {
    fallThrough(argv, `could not resolve a root: ${describe(error)}`);
  }

  try {
    switch (args.command) {
      case "ls": {
        const { projects, stale } = ls(ctx);
        if (projects.length === 0) {
          process.stdout.write(`no projects under ${ctx.resolved.root}\n`);
        }
        for (const p of projects) {
          const state = p.tab ? `tab ${p.tab.position}  ${p.panes} pane(s)  agent:${p.agent}` : "—";
          process.stdout.write(`  ${p.relPath.padEnd(24)} ${state}\n`);
        }
        for (const tab of stale) {
          process.stdout.write(`  ${tab.name.padEnd(24)} STALE (project gone)\n`);
        }
        return;
      }
      case "open": {
        const name = args.rest[0];
        if (!name) throw new Error("open needs a project name");
        open(ctx, name);
        return;
      }
      case "close": {
        const name = args.rest[0];
        if (!name) throw new Error("close needs a project name");
        close(ctx, name);
        return;
      }
      case "print": {
        const name = args.rest[0];
        if (!name) throw new Error("print needs a project name");
        process.stdout.write(print(ctx, name));
        return;
      }
      case "init": {
        const dir = args.rest[0] ?? process.cwd();
        process.stdout.write(`${initMessage(init(dir, { force: args.force }), dir)}\n`);
        return;
      }
      case "doctor": {
        const checks = report(gather({ client, depth: args.depth }));
        for (const check of checks) process.stdout.write(`${formatCheck(check)}\n`);
        const worst = worstLevel(checks);
        process.stdout.write(
          worst === "ok"
            ? "\nall good\n"
            : `\n${checks.filter((c) => c.level !== "ok").length} thing(s) to look at\n`,
        );
        process.exitCode = worst === "fail" ? 1 : 0;
        return;
      }
      default: {
        // Attaching needs a terminal. Without this guard the client panics in
        // os_input_output when stdin is a pipe, which is what happens whenever
        // `sl0ppi up` runs from a script or a CI step.
        const interactive = Boolean(process.stdin.isTTY && process.stdout.isTTY);
        const willAttach = interactive && !args.dryRun && sessionEnv !== ctx.resolved.session;

        // When we are going to attach anyway, create the session BY attaching:
        // background creation leaves a phantom client behind for the life of the
        // session (see UpResult.createWith).
        const result = up({ ...ctx, deferCreate: willAttach });

        // Inside the session already? Focusing beats nesting a second client.
        if (sessionEnv === ctx.resolved.session) {
          if (ctx.resolved.project) open(ctx, ctx.resolved.project);
          return;
        }
        if (args.dryRun) return;
        if (!willAttach) {
          process.stdout.write(`session ${ctx.resolved.session} ready (not a tty; not attaching)\n`);
          return;
        }

        const bin = process.env.SL0PPI_BIN ?? DEFAULT_BIN;
        const attachArgs = result.createWith
          ? ["--layout", result.createWith, "attach", "--create", ctx.resolved.session]
          : ["attach", ctx.resolved.session];
        const proc = spawnSync(bin, attachArgs, { stdio: "inherit" });
        process.exit(proc.status ?? 0);
      }
    }
  } catch (error) {
    // A UserError is an answer, not a malfunction: print it and stop. Handing
    // over to sl0ppij here would bury the explanation and start a session the
    // user never asked for.
    if (error instanceof UserError) {
      process.stderr.write(`sl0ppi: ${error.message}\n`);
      process.exit(1);
    }
    fallThrough(argv, describe(error));
  }
}

function describe(error: unknown): string {
  return error instanceof Error ? error.message : String(error);
}

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