"""
Mustache-aehnliche Platzhalter {{schluessel}} fuer KI-Templates aus ai_prompts.

Kein Vereinsbezug — reine Textersetzung; Aufrufe aus exercise_ai und Admin-Vorschau.
"""
from __future__ import annotations

import re
from dataclasses import dataclass
from typing import Dict, List, Mapping

_PLACEHOLDER_RE = re.compile(r"\{\{\s*([a-zA-Z0-9_]+)\s*\}\}")


def _placeholder_pattern_for_key(key: str) -> re.Pattern[str]:
    return re.compile(r"\{\{\s*" + re.escape(str(key).strip()) + r"\s*\}\}")


@dataclass(frozen=True)
class MustacheRenderResult:
    """Ergebnis von render_mustache_template."""

    text: str
    keys_in_template: List[str]
    keys_substituted: List[str]
    keys_missing_variables: List[str]
    placeholders_remaining: List[str]


def extract_mustache_keys(template: str) -> List[str]:
    """Platzhalter-Namen in Vorkommensreihenfolge, ohne erstes Duplikat."""
    seen: set[str] = set()
    ordered: List[str] = []
    for m in _PLACEHOLDER_RE.finditer(template or ""):
        k = str(m.group(1) or "").strip()
        if not k or k in seen:
            continue
        seen.add(k)
        ordered.append(k)
    return ordered


def render_mustache_template(template: str, variables: Mapping[str, str]) -> MustacheRenderResult:
    """
    Ersetzt {{keys}} durch die passenden Strings.
    Variablen, die fuer einen im Template genutzten Key fehlen, werden als Leerstring ersetzt.

    Rueckgabe-liste keys_missing_variables: Keys, die im Template vorkommen, aber nicht als Map-Keys
    uebergeben wurden (oder None-Wert entsprachen Leerung).
    """
    tpl_in = template or ""
    vars_norm: Dict[str, str] = {}
    for k, v in variables.items():
        vars_norm[str(k)] = "" if v is None else str(v)
    keys_in = extract_mustache_keys(tpl_in)
    missing_known: List[str] = []
    out = tpl_in
    substituted: List[str] = []

    for key in keys_in:
        pat = _placeholder_pattern_for_key(key)
        repl = vars_norm.get(key)
        if key not in vars_norm:
            missing_known.append(key)
            repl = ""
        substituted.append(key)
        out = pat.sub(repl, out)

    still = extract_mustache_keys(out)

    return MustacheRenderResult(
        text=out,
        keys_in_template=keys_in,
        keys_substituted=substituted,
        keys_missing_variables=missing_known,
        placeholders_remaining=still,
    )


def exercise_placeholder_catalog() -> dict:
    """
    Statischer Platzhalter-Katalog fuer Uebungs-KI-Templates — deckt aktuelle Seeds ab.
    (Erweiterung andere Kontexte: matrix/import folgen separat.)
    """
    defs = [
        {
            "key": "exercise_title",
            "placeholder": "{{exercise_title}}",
            "description": "Titel der Uebung (oder Platzhalter, wenn leer).",
            "used_by_slugs": ["exercise_summary", "exercise_skill_suggestions", "exercise_instruction_rewrite"],
        },
        {
            "key": "exercise_focus_area",
            "placeholder": "{{exercise_focus_area}}",
            "description": "Fokuskontext (Text-Hinweis aus Formular, optional).",
            "used_by_slugs": ["exercise_summary", "exercise_skill_suggestions", "exercise_instruction_rewrite"],
        },
        {
            "key": "exercise_goal",
            "placeholder": "{{exercise_goal}}",
            "description": "Ziel aus dem Formular, als Plaintext ohne HTML-Zeichen.",
            "used_by_slugs": ["exercise_summary", "exercise_skill_suggestions", "exercise_instruction_rewrite"],
        },
        {
            "key": "exercise_execution",
            "placeholder": "{{exercise_execution}}",
            "description": "Durchfuehrung als Plaintext ohne HTML-Zeichen.",
            "used_by_slugs": ["exercise_summary", "exercise_skill_suggestions", "exercise_instruction_rewrite"],
        },
        {
            "key": "exercise_preparation",
            "placeholder": "{{exercise_preparation}}",
            "description": "Vorbereitung/Aufbau als Plaintext ohne HTML.",
            "used_by_slugs": ["exercise_instruction_rewrite"],
        },
        {
            "key": "exercise_trainer_notes",
            "placeholder": "{{exercise_trainer_notes}}",
            "description": "Trainer-Hinweise als Plaintext ohne HTML.",
            "used_by_slugs": ["exercise_instruction_rewrite"],
        },
        {
            "key": "skills_catalog",
            "placeholder": "{{skills_catalog}}",
            "description": (
                "Gewichtete, kontextbezogene Liste aus dem Skill-Katalog (retrieval_profiles). "
                "Nur fuer exercise_skill_suggestions."
            ),
            "used_by_slugs": ["exercise_skill_suggestions"],
        },
    ]
    return {"context": "exercise", "placeholders": defs}


__all__ = [
    "MustacheRenderResult",
    "exercise_placeholder_catalog",
    "extract_mustache_keys",
    "render_mustache_template",
]