"""Locked system-prompt builder (PLAN §6).

The persona + HONESTY GATE text is **locked verbatim** — change it through
the plan, not here. Two modes:

* ``HIGH`` — grounded turn: full top-document texts under ``<documents>``.
* ``LOW``  — deflection turn: weak-hit *titles only* plus the
  ``DEFLECT_MODE`` marker (the E2E mock LLM keys on that marker).
"""
from __future__ import annotations

from collections.abc import Sequence

from app.models import Document

#: PLAN §6 verbatim (line wrapping included); ``{relevance}`` is filled by
#: :func:`_base`.
PERSONA: str = (
    'You are "Brain of Reese" — the digital brain of Reese, a self-hoster and\n'
    "homelab tinkerer. Personality: chippy, upbeat, warm, and genuinely\n"
    'optimistic about the user\'s ability to do things ("you\'ve got this").\n'
    "\n"
    "Rules:\n"
    "1. Answer ONLY from the provided document context. Cite which document(s)\n"
    "   you used, by path.\n"
    "2. Be concrete: names, versions, ports, hosts, schedules — the specifics in\n"
    "   the docs are the value.\n"
    '3. HONESTY GATE: if <relevance> is "LOW", you must NOT pretend to know.\n'
    '   Start your answer with a variant of: "I haven\'t done anything like that."\n'
    "   Then offer 2-3 alternative questions about things you DO have notes on.\n"
    "4. Never invent facts, hosts, or steps that are not in the context.\n"
    "5. Keep answers tight: short paragraphs, bullets where helpful.\n"
    "\n"
    "<relevance>{relevance}</relevance>"
)


def _base(relevance: str) -> str:
    if relevance not in ("HIGH", "LOW"):
        raise ValueError(f"relevance must be HIGH or LOW, got {relevance!r}")
    return PERSONA.replace("{relevance}", relevance)


def build_high_prompt(documents: Sequence[Document]) -> str:
    """Grounded turn: locked persona + full texts of the top documents."""
    blocks = [
        f'<document source="{doc.source}" path="{doc.path}" title="{doc.title}">\n'
        f"{doc.content}\n"
        "</document>"
        for doc in documents
    ]
    body = "\n\n".join(blocks) if blocks else (
        "(no documents matched — do not invent specifics)"
    )
    return _base("HIGH") + "\n<documents>\n" + body + "\n</documents>"


def build_deflect_prompt(titles: Sequence[str]) -> str:
    """Deflection turn: weak-hit titles only (no document content)."""
    weak = "\n".join(f"- {t}" for t in titles) if titles else "(nothing close at all)"
    return (
        _base("LOW")
        + "\nDEFLECT_MODE: retrieval was weak — the titles below are the closest "
        "your notes come to the question. They are titles only; do not pretend "
        "they answer it. Use them to propose 2-3 alternative questions.\n"
        + weak
    )