"""Minimal HTTP file server with Range support, for local verification only.

Python's stdlib SimpleHTTPRequestHandler does not honor `Range:` requests, but
cdx_toolkit fetches WARC records by byte range, so we need one. Serves files under
a root directory; supports single-range `bytes=start-end` requests (206) which is
all cdx_toolkit issues.

Usage: python scripts/range_server.py <root_dir> <port>
"""
from __future__ import annotations

import os
import sys
from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer


def make_handler(root: str):
    root = os.path.abspath(root)

    class RangeHandler(BaseHTTPRequestHandler):
        def log_message(self, *args):  # quiet
            pass

        def _resolve(self):
            path = self.path.split("?", 1)[0].lstrip("/")
            full = os.path.abspath(os.path.join(root, path))
            if not full.startswith(root) or not os.path.isfile(full):
                return None
            return full

        def do_HEAD(self):
            full = self._resolve()
            if full is None:
                self.send_error(404)
                return
            size = os.path.getsize(full)
            self.send_response(200)
            self.send_header("Content-Length", str(size))
            self.send_header("Accept-Ranges", "bytes")
            self.end_headers()

        def do_GET(self):
            full = self._resolve()
            if full is None:
                self.send_error(404)
                return
            size = os.path.getsize(full)
            rng = self.headers.get("Range")
            if rng and rng.startswith("bytes="):
                start_s, _, end_s = rng[len("bytes="):].partition("-")
                start = int(start_s) if start_s else 0
                end = int(end_s) if end_s else size - 1
                end = min(end, size - 1)
                length = end - start + 1
                with open(full, "rb") as f:
                    f.seek(start)
                    data = f.read(length)
                self.send_response(206)
                self.send_header("Content-Range", f"bytes {start}-{end}/{size}")
                self.send_header("Content-Length", str(len(data)))
                self.send_header("Accept-Ranges", "bytes")
                self.end_headers()
                self.wfile.write(data)
            else:
                with open(full, "rb") as f:
                    data = f.read()
                self.send_response(200)
                self.send_header("Content-Length", str(len(data)))
                self.send_header("Accept-Ranges", "bytes")
                self.end_headers()
                self.wfile.write(data)

    return RangeHandler


if __name__ == "__main__":
    root = sys.argv[1] if len(sys.argv) > 1 else "tests/fixtures/cc"
    port = int(sys.argv[2]) if len(sys.argv) > 2 else 8080
    server = ThreadingHTTPServer(("0.0.0.0", port), make_handler(root))
    print(f"serving {os.path.abspath(root)} on :{port} (Range-capable)", flush=True)
    server.serve_forever()