"""Global rank computation for the leaderboard tabs.

Ranks are computed once at startup over the full model list, before any
filtering or partitioning into Open-Weight / Proprietary tables.
They are properties of the model on this benchmark version and do not
change when users apply filters or re-sort interactively.

Tie handling: standard competition ranking ("1224").
    scores 70, 65, 65, 60 → ranks 1, 2, 2, 4

Module-level export
-------------------
GLOBAL_RANKS : dict[str, dict[str, int]]
    Keyed by the short pillar names from config.PILLARS:
    'overall', 'spatial', 'st', 'temporal', 'semantic'.
    Populated the first time compute_global_ranks() is called at startup.
    Import directly::

        from util.ranking import GLOBAL_RANKS
"""

from __future__ import annotations

from typing import Iterable

from .config import HEADLINE_FIELD_BY_TAB
from .data import ModelRecord

# Map short pillar key (config.PILLARS) → score field in ModelRecord.scores.
# 'st' is the short form of 'spatio_temporal' used by the new UI layer.
_PILLAR_SCORE_FIELD: dict[str, str] = {
    "overall":  "overall",
    "spatial":  "spatial",
    "st":       "spatio_temporal",
    "temporal": "temporal",
    "semantic": "semantic",
}

# Module-level export. Starts empty; populated by compute_global_ranks()
# on the first (and only) call at app startup.
GLOBAL_RANKS: dict[str, dict[str, int]] = {}


# -- Core ranking primitive ------------------------------------------------


def _rank_models(models: list[ModelRecord], score_field: str) -> dict[str, int]:
    """Return ``{model_id: rank}`` using 1-2-2-4 competition ranking.

    Sort key: descending score, ascending name as deterministic tiebreaker.
    The score field must be present in every model's scores dict.
    """
    sorted_models = sorted(
        models,
        key=lambda m: (-_headline(m, score_field), m.name),
    )
    ranks: dict[str, int] = {}
    prev_score: float | None = None
    prev_rank: int = 0
    for position, m in enumerate(sorted_models, start=1):
        s = m.scores[score_field]
        if prev_score is not None and s == prev_score:
            ranks[m.id] = prev_rank
        else:
            ranks[m.id] = position
            prev_rank = position
            prev_score = s
    return ranks


# -- Public API ------------------------------------------------------------


def compute_global_ranks(
    models: list[ModelRecord], tabs: Iterable[str]
) -> dict[str, dict[str, int]]:
    """Return ``{tab: {model_id: rank}}`` with global standard-competition ranks.

    Sort key per tab: descending by the tab's headline score, ascending by
    model name as deterministic tiebreaker. Required score fields are
    guaranteed present by upstream validation.

    Side-effect: populates the module-level ``GLOBAL_RANKS`` dict using the
    short pillar keys from ``config.PILLARS`` ('overall', 'spatial', 'st',
    'temporal', 'semantic'). This happens once at app startup so any module
    can ``from util.ranking import GLOBAL_RANKS`` after startup.
    """
    # Build return value keyed by caller-supplied tab names (backward-compat).
    result: dict[str, dict[str, int]] = {}
    for tab in tabs:
        field = HEADLINE_FIELD_BY_TAB[tab]
        result[tab] = _rank_models(models, field)

    # Populate GLOBAL_RANKS with short pillar keys for the new UI layer.
    for pillar_key, score_field in _PILLAR_SCORE_FIELD.items():
        GLOBAL_RANKS[pillar_key] = _rank_models(models, score_field)

    return result


def sort_model_ids_by_rank(
    model_ids: Iterable[str], rank_map: dict[str, int]
) -> list[str]:
    """Return ``model_ids`` sorted by ascending rank.

    Ids missing from ``rank_map`` are placed last in their input order.
    """
    sentinel = float("inf")
    return sorted(model_ids, key=lambda mid: rank_map.get(mid, sentinel))


def _headline(m: ModelRecord, field: str) -> float:
    # Required scores guaranteed by validation; defensive default keeps
    # this function total in case it is called pre-validation.
    v = m.scores.get(field)
    return v if v is not None else float("-inf")