"""Computes modifiers, derived stats, skill totals and carried weight (mirror of frontend/src/calc.js)."""


def kit_items(ch: dict, rules: dict) -> list:
    """Returns [(label, item, qty)] for the starting kit and extra items."""
    items = {e["id"]: e for e in rules.get("equipment", [])}
    kit = ch.get("kit") or {}
    out = []
    for label, key in (("Weapon", "weapon"), ("Armor", "armor"), ("Tool", "tool")):
        if kit.get(key) in items:
            out.append((label, items[kit[key]], 1))
    for rid in kit.get("resources", []):
        if rid in items:
            out.append(("Resource", items[rid], 1))
    for iid, qty in (kit.get("extras") or {}).items():
        if iid in items and int(qty) > 0:
            out.append(("Extra", items[iid], int(qty)))
    return out


def compute(ch: dict, rules: dict) -> dict:
    cr = {**rules["creation"], **(ch.get("creation") or {})}  # per-character rules preset overrides
    prof_id = ch.get("profession")
    bonus_attr = ch.get("profession_bonus_attr") if prof_id else None

    attrs = {}
    for a in rules["attributes"]:
        base = int((ch.get("attributes") or {}).get(a["id"], cr["attr_start"]))
        attrs[a["id"]] = base + (cr["profession_attr_bonus"] if a["id"] == bonus_attr else 0)
    mods = {k: v // 10 for k, v in attrs.items()}

    derived = {d["id"]: sum(mods[x] for x in d["formula"]) for d in rules["derived"]}

    skills = []
    for s in rules["skills"]:
        pts = int((ch.get("skill_points") or {}).get(s["id"], 0))
        # Proficiency "pips": 1 from the profession plus free picks, at most 2 (2 = Expertise)
        prof_pip = 1 if (ch.get("proficiencies") or {}).get(s["id"]) else 0
        free_pips = min(int((ch.get("proficiency_picks") or {}).get(s["id"], 0)), cr.get("max_proficiency_pips", 2) - prof_pip)
        pips = prof_pip + max(0, free_pips)
        prof = [0, cr["proficiency_bonus"], cr["expertise_bonus"]][pips]
        unlocked = s["id"] in (ch.get("unlocked") or [])
        usable = s["type"] == "basic" or unlocked or prof > 0  # advanced skills must be unlocked
        best = max(attrs[a] for a in s["attrs"])  # with several attributes the higher one counts
        skills.append({**s, "points": pts, "prof": prof, "pips": pips, "usable": usable, "unlocked": unlocked,
                       "total": best + pts + prof})

    aug_by_id = {a["id"]: a for a in rules["augments"]}
    chosen = [aug_by_id[i] for i in ch.get("augments", []) if i in aug_by_id]
    used = sum(a["cost"] for a in chosen)

    weight = round(sum(item["kg"] * qty for _, item, qty in kit_items(ch, rules)), 1)

    return {"attrs": attrs, "mods": mods, "derived": derived, "skills": skills,
            "capacity_used": used, "capacity_max": derived.get("augmentation", 0),
            "augments": chosen, "weight": weight,
            "carry_max": max(0, mods["strength"]) * cr.get("carry_per_strength_mod", 10)}