"""Persistent state for the order form (one JSON file in WORK_DIR volume).

Per project (keyed by Kód zakázky) we keep:
  - nazev: Název zakázky
  - last:  {field: last-used value}     → used to prefill
  - hist:  {field: {value: count}}      → all values ever used, with counts
                                          (so the UI can offer them, most-used
                                           on top)

Plus global meta: last order number (for the +1 suggestion).
"""
import json
import os
import re
import threading
from pathlib import Path

_STORE = Path(os.getenv("WORK_DIR", "/tmp/offer-to-order")) / "order_state.json"
_lock = threading.Lock()

# Fields remembered per project (Název is stored separately as "nazev").
STICKY = [
    "misto_dodani", "kontaktni_osoba", "vystavil",
    "splatnost", "zaruka", "zpusob_platby", "zpusob_odberu", "zpusob_dopravy",
    "forma_objednavky", "fakturujte", "popis",
]


def _load() -> dict:
    try:
        d = json.loads(_STORE.read_text(encoding="utf-8"))
    except Exception:
        d = {}
    d.setdefault("projects", {})
    d.setdefault("meta", {})
    return d


def _save(d: dict) -> None:
    _STORE.parent.mkdir(parents=True, exist_ok=True)
    _STORE.write_text(json.dumps(d, ensure_ascii=False, indent=2), encoding="utf-8")


def _normalize(rec: dict) -> dict:
    """Upgrade an old flat-style record to the {nazev,last,hist} shape."""
    if "last" in rec or "hist" in rec:
        rec.setdefault("last", {})
        rec.setdefault("hist", {})
        return rec
    nazev = rec.get("nazev", "")
    last, hist = {}, {}
    for k in STICKY:
        if rec.get(k) not in (None, ""):
            last[k] = rec[k]
            hist[k] = {rec[k]: 1}
    return {"nazev": nazev, "last": last, "hist": hist}


# ── Projects ──
def list_projects() -> list[dict]:
    projects = _load()["projects"]
    return sorted(
        [{"kod": k, "nazev": _normalize(v).get("nazev", "")}
         for k, v in projects.items()],
        key=lambda p: p["kod"].lower(),
    )


def get_defaults(code: str) -> dict:
    """Prefill values (last used) + a _history map ranked most-used first."""
    code = (code or "").strip()
    if not code:
        return {}
    raw = _load()["projects"].get(code)
    if not raw:
        return {}
    rec = _normalize(raw)
    out = dict(rec["last"])
    if rec.get("nazev"):
        out["nazev_zakazky"] = rec["nazev"]
    history = {}
    for field, counts in rec.get("hist", {}).items():
        ranked = sorted(counts.items(), key=lambda kv: -kv[1])
        history[field] = [{"value": v, "count": c} for v, c in ranked]
    out["_history"] = history
    return out


def upsert_project(code: str, nazev: str) -> None:
    code = (code or "").strip()
    if not code:
        return
    with _lock:
        d = _load()
        rec = _normalize(d["projects"].get(code, {}))
        rec["nazev"] = (nazev or "").strip()
        d["projects"][code] = rec
        _save(d)


def delete_project(code: str) -> None:
    code = (code or "").strip()
    with _lock:
        d = _load()
        if code in d["projects"]:
            del d["projects"][code]
            _save(d)


def delete_history_value(code: str, field: str, value: str) -> None:
    """Remove one remembered value from a project field's history."""
    code = (code or "").strip()
    if not code or not field:
        return
    with _lock:
        d = _load()
        raw = d["projects"].get(code)
        if not raw:
            return
        rec = _normalize(raw)
        counts = rec["hist"].get(field)
        if counts and value in counts:
            del counts[value]
            if not counts:
                rec["hist"].pop(field, None)
        if rec["last"].get(field) == value:
            remaining = rec["hist"].get(field)
            if remaining:
                rec["last"][field] = max(remaining, key=remaining.get)
            else:
                rec["last"].pop(field, None)
        d["projects"][code] = rec
        _save(d)


def save_defaults(code: str, order: dict) -> None:
    """Record sticky-field values for a project: update 'last' and bump the
    frequency count in 'hist' for each non-empty value."""
    code = (code or "").strip()
    if not code:
        return
    with _lock:
        d = _load()
        rec = _normalize(d["projects"].get(code, {}))
        if order.get("nazev_zakazky"):
            rec["nazev"] = order["nazev_zakazky"]
        for k in STICKY:
            v = order.get(k)
            if v in (None, ""):
                continue
            v = str(v)
            rec["last"][k] = v
            rec["hist"].setdefault(k, {})
            rec["hist"][k][v] = rec["hist"][k].get(v, 0) + 1
        d["projects"][code] = rec
        _save(d)


# ── Order-number counter ──
def next_order_number() -> str:
    return _increment(_load()["meta"].get("last_order_number") or "")


def _increment(s: str) -> str:
    if not s:
        return ""
    m = re.search(r"(\d+)(\D*)$", s)
    if not m:
        return s
    num = m.group(1)
    return s[: m.start(1)] + str(int(num) + 1).zfill(len(num)) + m.group(2)


def remember_order_number(num: str) -> None:
    num = (num or "").strip()
    if not num:
        return
    with _lock:
        d = _load()
        d["meta"]["last_order_number"] = num
        _save(d)