"""Field-assist entrypoint — llm_setup.llm_call only.

Pure module: no FastAPI imports and no HTTPException.
Called from job.app's POST /job/assist-field route; no HTTP surface of its own.

ValueError means the request itself is bad (unknown field/action, nothing to
fix) and maps to 422 at the route. RuntimeError means the model could not be
consulted or returned something unusable and maps to 503 — the route must not
echo its message to the client, since it can carry provider detail.
"""

from __future__ import annotations

import logging

from job_assist.decorators import parse_assist_response
from job_assist.prompt import ACTIONS, FIELD_RULES, SYSTEM_PROMPT, user_prompt
from llm_setup import llm_call

logger = logging.getLogger("job_assist")

# A suggestion is only writable once these context fields exist — without the
# role and its seniority the model can only produce generic filler.
# "experience" is satisfied by either end of the range.
SUGGEST_ANCHORS = {
    "department": ("title",),
    "location": ("title",),
    "salary": ("title", "experience"),
    "requirements": ("title", "experience"),
    "optional_skills": ("title", "experience"),
    "description": ("title", "experience"),
}

_ANCHOR_LABELS = {"title": "job title", "experience": "experience range"}


def _has_anchor(context, key) -> bool:
    ctx = context or {}
    if key == "experience":
        return any(str(ctx.get(k) or "").strip() for k in ("experience_min", "experience_max"))
    return bool(str(ctx.get(key) or "").strip())


async def run_field_assist(*, field, action, text="", context=None) -> str:
    if field not in FIELD_RULES:
        raise ValueError(f"unsupported field: {field}")
    if action not in ACTIONS:
        raise ValueError(f"unsupported action: {action}")
    if action == "fix" and not (text or "").strip():
        raise ValueError("nothing to fix: the field is empty")
    if action == "suggest":
        if field == "title":
            ctx_values = (context or {}).values()
            if not (text or "").strip() and not any(str(v or "").strip() for v in ctx_values):
                raise ValueError("type a draft title or fill in another field first")
        else:
            missing = [a for a in SUGGEST_ANCHORS[field] if not _has_anchor(context, a)]
            if missing:
                names = " and ".join(_ANCHOR_LABELS[a] for a in missing)
                raise ValueError(f"fill in the {names} first")

    try:
        data = await llm_call(
            SYSTEM_PROMPT,
            user_prompt(field, action, text, context),
            json_mode=True,
        )
        return parse_assist_response(data, field)
    except Exception as e:
        # Log the type only — the message can carry prompt or form content.
        logger.warning("field assist failed: field=%s action=%s exc=%s", field, action, type(e).__name__)
        raise RuntimeError("field assist failed") from e