"""Load prompts from files instead of Python string constants.

Two reasons this is worth the indirection:

* Prompts are the main thing a fork for another parliament has to rewrite, and
  editing Markdown is a different job from editing Python.
* With PROMPTS_RELOAD=1 the files are re-read on every call, so prompt iteration
  no longer needs a server restart.

Placeholders use ``$name`` / ``${name}`` (:class:`string.Template`), **not**
``{name}``. Several prompts embed literal JSON braces, which ``str.format`` would
raise on; and ``safe_substitute`` leaves an unknown placeholder alone rather than
killing a live chat turn over a typo.

    from prompts_loader import load_prompt
    ORCHESTRATOR_SYSTEM = load_prompt("chat/orchestrator")
"""
from __future__ import annotations

import os
import re
from datetime import date
from functools import lru_cache
from pathlib import Path
from string import Template
from typing import Any

from parliament import PARLIAMENT

_ROOT = Path(__file__).resolve().parent
PROMPTS_DIR = Path(os.environ.get("PROMPTS_DIR") or _ROOT / "prompts")

# {{include:path/to/partial}} — expanded before substitution so a shared block
# (the schema reference, say) has exactly one source.
_INCLUDE_RE = re.compile(r"^[ \t]*\{\{include:([\w/\-.]+)\}\}[ \t]*$", re.MULTILINE)

_MAX_INCLUDE_DEPTH = 5


class PromptNotFound(FileNotFoundError):
    pass


def _reload_enabled() -> bool:
    return os.environ.get("PROMPTS_RELOAD", "").lower() in {"1", "true", "yes"}


def _candidates(name: str) -> list[Path]:
    """Language directory first, then the language-neutral and English fallbacks."""
    lang = PARLIAMENT.language.prompt_language
    return [
        PROMPTS_DIR / lang / f"{name}.md",
        PROMPTS_DIR / f"{name}.md",
        PROMPTS_DIR / "en" / f"{name}.md",
    ]


def _resolve(name: str) -> Path:
    for path in _candidates(name):
        if path.exists():
            return path
    tried = "\n  ".join(str(p) for p in _candidates(name))
    raise PromptNotFound(f"No prompt named {name!r}. Looked in:\n  {tried}")


def _expand_includes(text: str, depth: int = 0) -> str:
    if depth >= _MAX_INCLUDE_DEPTH:
        raise RecursionError(f"{{{{include:}}}} nested more than {_MAX_INCLUDE_DEPTH} deep")

    def replace(match: re.Match) -> str:
        return _expand_includes(_resolve(match.group(1)).read_text(encoding="utf-8"), depth + 1)

    return _INCLUDE_RE.sub(replace, text)


def base_context() -> dict[str, Any]:
    """Values available to every prompt without being passed explicitly.

    Domain words come from `vocabulary:` so a prompt can say "$speech_plural"
    and read naturally in any parliament's own language.
    """
    ids = PARLIAMENT.ids
    return {
        "parliament_name": PARLIAMENT.meta.get("name", ""),
        "parliament_name_en": PARLIAMENT.meta.get("name_en", ""),
        "country": PARLIAMENT.meta.get("country", ""),
        "data_start_year": PARLIAMENT.meta.get("data_start_year", ""),
        "fts_config": PARLIAMENT.language.fts_config,
        "answer_language": PARLIAMENT.language.name_en or PARLIAMENT.language.prompt_language,
        "answer_language_native": PARLIAMENT.language.name or PARLIAMENT.language.prompt_language,
        "preserve_characters": PARLIAMENT.language.preserve_characters,
        "party_codes": ", ".join(PARLIAMENT.party_codes),
        "date_today": date.today().isoformat(),
        "person_id_example": ids.get("person_id", {}).get("example", ""),
        "speech_id_example": ids.get("speech_id", {}).get("example", ""),
        "doc_id_example": ids.get("doc_id", {}).get("example", ""),
        "debate_id_example": ids.get("debate_id", {}).get("example", ""),
        **PARLIAMENT.vocabulary,
    }


@lru_cache(maxsize=None)
def _load_cached(name: str) -> str:
    return _expand_includes(_resolve(name).read_text(encoding="utf-8"))


def load_prompt(name: str, **extra: Any) -> str:
    """Return a prompt with placeholders filled in.

    Args:
        name: Path under prompts/ without the .md suffix, e.g. "chat/orchestrator".
        **extra: Additional placeholder values, overriding the base context.
    """
    raw = _expand_includes(_resolve(name).read_text(encoding="utf-8")) if _reload_enabled() \
        else _load_cached(name)
    return Template(raw).safe_substitute({**base_context(), **extra})


def tool_doc(name: str, **extra: Any) -> str:
    """Load a tool description from prompts/tools/<name>.md.

    Passed as ``@register_tool(description=...)``, which overrides the docstring
    description while leaving ``Args:`` parsing to the docstring — so the country-
    specific prose lives in a file without disturbing schema generation.
    """
    return load_prompt(f"tools/{name}", **extra)


def clear_cache() -> None:
    _load_cached.cache_clear()