from __future__ import annotations

from collections.abc import Awaitable, Callable

from .render import build_segments

# Text types that get the rendered viewer; anything else is served untouched.
VIEWABLE_CONTENT_TYPES = {'text/plain', 'text/markdown'}

_TRUTHY = {'1', 'true', 'yes'}

def _base_content_type(content_type: str) -> str:
  return (content_type or '').split(';')[0].strip().lower()

def wants_text_view(content_type: str, accept_header: str, raw_param: str | None, force_download: bool) -> bool:
  """Only real browser navigations get HTML; curl, wget and the CLI keep the raw bytes."""
  if force_download or (raw_param or '').lower() in _TRUTHY:
    return False
  if _base_content_type(content_type) not in VIEWABLE_CONTENT_TYPES:
    return False
  # Accept: */* (curl, wget, CLI clients) must not trigger the viewer.
  return 'text/html' in (accept_header or '').lower()

def decode_text(raw: bytes) -> str:
  """Decode the full document; invalid bytes become replacement characters."""
  return raw.decode('utf-8', errors='replace')

async def build_view_context(
  raw: bytes,
  file_name: str,
  host: str,
  root_path: str,
  raw_url: str,
  lookup: Callable[[str], Awaitable[dict | None]] | None,
) -> dict:
  text = decode_text(raw)
  segments = await build_segments(text, host=host, root_path=root_path, lookup=lookup)
  return {
    'file_name': file_name,
    'segments': segments,
    'raw_url': raw_url,
  }