"""Align optional time-spent-with-patient to specialty duration rules.

Paediatrics (26) has hard Schedule minima for special / extended /
neurodevelopmental consults and developmental K-units. Family Practice (00)
assessments are content-defined (not hard minute floors); time spent only
steers BM25 toward the matching office ladder rung.

When time spent is omitted, no duration filtering is applied.
"""
from __future__ import annotations

import re
from dataclasses import dataclass

from .specialty_registry import normalize_specialty_code

# Hard minimum direct-contact minutes from PAEDIATRICS (26) / GENERAL LISTINGS.
_MIN_MINUTES_BY_CODE: dict[str, int] = {
    # Special paediatric consultation
    "A260": 75,
    "C260": 75,
    "W260": 75,
    # Extended special paediatric consultation
    "A662": 90,
    "C662": 90,
    "W662": 90,
    # Neurodevelopmental consultation
    "A667": 90,
    "A695": 90,
    "C667": 90,
    "C695": 90,
    "W667": 90,
    "W695": 90,
    # Developmental / behavioural care — first unit (≥ 20 min of a 30-min unit)
    "K122": 20,
    "K123": 20,
}

# Description cues for codes whose indexed text mentions a minute floor but
# may not be in the allowlist above (future SoB additions).
_DESC_MIN_PATTERNS: list[tuple[re.Pattern[str], int]] = [
    (
        re.compile(
            r"minimum\s+of\s+ninety\s+minutes|minimum\s+of\s+90\s+minutes|"
            r"spends?\s+a\s+minimum\s+of\s+90\s+minutes",
            re.I,
        ),
        90,
    ),
    (
        re.compile(
            r"minimum\s+of\s+seventy[- ]?five\s+minutes|"
            r"minimum\s+of\s+75\s+minutes|"
            r"spends?\s+a\s+minimum\s+of\s+75\s+minutes",
            re.I,
        ),
        75,
    ),
    (
        re.compile(
            r"minimum\s+of\s+fifty\s+minutes|minimum\s+of\s+50\s+minutes",
            re.I,
        ),
        50,
    ),
    (
        re.compile(r"\bper\s+unit\b", re.I),
        20,  # GP ½-hour unit services: first unit needs ≥ 20 minutes
    ),
]


@dataclass(frozen=True)
class DurationAlignment:
    minutes: int
    label: str
    keywords: str


def align_time_spent(
    minutes: int | None,
    specialty_code: str | None = None,
) -> DurationAlignment | None:
    """Build steering keywords / label for clinician-reported time with patient."""
    if minutes is None or minutes < 0:
        return None
    specialty = normalize_specialty_code(specialty_code)
    if specialty == "00":
        return _align_time_spent_family_practice(minutes)
    return _align_time_spent_paediatrics(minutes)


def _align_time_spent_family_practice(minutes: int) -> DurationAlignment:
    """Soft ladder steer for FP — no invented hard minute floors."""
    if minutes < 15:
        label = f"{minutes} minutes with patient (brief)"
        keywords = (
            f"brief minor assessment A001 mini assessment A008 "
            f"Family Practice {minutes} minutes"
        )
    elif minutes < 35:
        label = f"{minutes} minutes with patient"
        keywords = (
            f"intermediate assessment A007 minor assessment A001 "
            f"Family Practice {minutes} minutes"
        )
    else:
        label = f"{minutes} minutes with patient"
        keywords = (
            f"general assessment A003 intermediate assessment A007 "
            f"periodic health K017 Family Practice {minutes} minutes"
        )
    return DurationAlignment(minutes=minutes, label=label, keywords=keywords)


def _align_time_spent_paediatrics(minutes: int) -> DurationAlignment:
    if minutes < 20:
        label = f"{minutes} minutes with patient (brief)"
        keywords = (
            "brief level 1 paediatric assessment short visit "
            f"{minutes} minutes"
        )
    elif minutes < 75:
        label = f"{minutes} minutes with patient"
        keywords = (
            "level 1 level 2 paediatric assessment medical specific "
            f"consultation {minutes} minutes direct contact"
        )
    elif minutes < 90:
        label = f"{minutes} minutes with patient (special consult eligible)"
        keywords = (
            "special paediatric consultation minimum 75 minutes "
            f"level 2 medical specific {minutes} minutes direct contact"
        )
    else:
        label = f"{minutes} minutes with patient (extended/neurodevelopmental eligible)"
        keywords = (
            "extended special paediatric consultation neurodevelopmental "
            "consultation minimum 90 minutes developmental behavioural care "
            f"{minutes} minutes direct contact"
        )
    return DurationAlignment(minutes=minutes, label=label, keywords=keywords)


def code_min_minutes(doc: dict) -> int | None:
    """Return the Schedule minimum direct-contact minutes for this code, if any."""
    code = (doc.get("billing_code") or "").upper()
    if code in _MIN_MINUTES_BY_CODE:
        return _MIN_MINUTES_BY_CODE[code]
    text = " ".join(
        [
            doc.get("description_text") or "",
            doc.get("description") or "",
            doc.get("rules_and_constraints") or "",
        ]
    )
    if not text.strip():
        return None
    for pattern, mins in _DESC_MIN_PATTERNS:
        if pattern.search(text):
            return mins
    return None


def code_applies_to_duration(doc: dict, minutes: int) -> bool:
    """True if this code is eligible given time spent with the patient.

    Codes without a Schedule minimum always apply. Minimum-time services are
    eligible only when ``minutes`` meets or exceeds their floor.
    """
    required = code_min_minutes(doc)
    if required is None:
        return True
    return minutes >= required


def filter_docs_for_duration(docs: list[dict], minutes: int) -> list[dict]:
    """Drop minimum-time codes the reported duration cannot support."""
    return [d for d in docs if code_applies_to_duration(d, minutes)]


def k_units_for_minutes(minutes: int) -> int:
    """How many ½-hour developmental/behavioural units the time supports.

    General Preamble table (30-minute units, major part thereof):
      1→20, 2→46, 3→76, 4→106, 5→136, 6→166, 7→196, 8→226 minutes.
    """
    thresholds = (20, 46, 76, 106, 136, 166, 196, 226)
    units = 0
    for i, need in enumerate(thresholds, start=1):
        if minutes >= need:
            units = i
        else:
            break
    return units


def duration_hint_for_llm(
    align: DurationAlignment,
    specialty_code: str | None = None,
) -> str:
    """Clinician-facing / LLM hint describing duration eligibility."""
    specialty = normalize_specialty_code(specialty_code)
    if specialty == "00":
        return _duration_hint_family_practice(align)
    return _duration_hint_paediatrics(align)


def _duration_hint_family_practice(align: DurationAlignment) -> str:
    mins = align.minutes
    lines = [
        f"{align.label}.",
        "Family Practice office assessments are content-defined (not hard "
        "minute floors). Prefer the ladder rung that matches the documented "
        "service: mini A008 → minor A001 → intermediate A007 → general A003 "
        "→ re-assessment A004 / periodic health K017.",
    ]
    if mins < 15:
        lines.append(
            "Brief contact — prefer minor A001 or mini A008 unless the note "
            "documents a fuller intermediate or general assessment."
        )
    elif mins < 35:
        lines.append(
            "Prefer intermediate A007 or minor A001; do not recommend general "
            "assessment A003 / periodic K017 unless the note documents those "
            "elements."
        )
    else:
        lines.append(
            "Longer visit — general assessment A003 or periodic health K017 "
            "may apply when the note documents those elements."
        )
    return " ".join(lines)


def _duration_hint_paediatrics(align: DurationAlignment) -> str:
    mins = align.minutes
    lines = [
        f"{align.label}.",
        "Only recommend Paediatrics codes whose Schedule minimum direct-contact "
        "time is met (or that have no minimum-time requirement).",
        "Hard floors from the current Schedule:",
        "  • Special paediatric consultation (A260/C260/W260): ≥ 75 minutes",
        "  • Extended special paediatric consultation (A662/C662/W662): ≥ 90 minutes",
        "  • Neurodevelopmental consultation (A667/A695 and setting mirrors): ≥ 90 minutes",
        "  • Developmental/behavioural care (K122/K123): ≥ 20 minutes for 1 unit",
    ]
    units = k_units_for_minutes(mins)
    if units:
        lines.append(
            f"Reported time supports up to {units} K122/K123 unit(s) "
            "(½ hour or major part thereof)."
        )
    else:
        lines.append(
            "Reported time is below 20 minutes — do not recommend K122/K123 "
            "unit services."
        )
    if mins < 75:
        lines.append(
            "Do not recommend special / extended / neurodevelopmental "
            "consultations — time spent is below their Schedule minima."
        )
    elif mins < 90:
        lines.append(
            "Special paediatric consultation (≥ 75 min) may apply; extended "
            "special and neurodevelopmental consultations still require ≥ 90 min."
        )
    else:
        lines.append(
            "Time spent meets minima for special, extended special, and "
            "neurodevelopmental consultations when other elements are met."
        )
    if mins < 20:
        lines.append(
            "Prefer Level 1 paediatric assessment (A261) for brief encounters "
            "unless the note clearly documents a more extensive Level 2 exam."
        )
    return " ".join(lines)