"""Snapshot and ring-drain helper mixin for the main GUI window."""

from __future__ import annotations

from pathlib import Path
import time

from PyQt6.QtWidgets import QFileDialog


class AppWindowSnapshotMixin:
    """Saves runtime data snapshots and maintains ring-reader freshness."""

    def _save_snapshot(self) -> None:
        """Save runtime snapshot in numpy-directory format."""
        self._drain_runtime_rings_for_snapshot()

        if not self._raw_history and not self._pre_history and not self._result_history:
            self._show_error("No runtime data is available for save")
            return

        try:
            last_n = int(self._save_count.value())
            output_root = Path(self._save_path_input.text().strip()).expanduser()
            snapshot_name = self._save_name_input.text().strip()
            snapshot_dir, summary = self._store.save_runtime_snapshot_numpy(
                output_root,
                snapshot_name,
                list(self._raw_history),
                list(self._pre_history),
                list(self._result_history),
                last_n,
            )
            self._log(
                f"Saved numpy snapshot: {snapshot_dir} "
                f"(raw={summary.get('raw_count', 0)}, "
                f"preprocessed={summary.get('preprocessed_count', 0)}, "
                f"results={summary.get('result_count', 0)}, "
                f"mode={summary.get('selection_mode', 'unknown')})"
            )
        except Exception as exc:  # noqa: BLE001
            self._show_error(f"Failed to save snapshot: {exc}")

    def _browse_save_path(self) -> None:
        """Open directory picker for snapshot output path."""
        selected = QFileDialog.getExistingDirectory(
            self,
            "Select Snapshot Directory",
            self._save_path_input.text().strip() or str(self._project_root),
        )
        if selected:
            self._save_path_input.setText(selected)

    def _drain_runtime_rings_for_snapshot(self) -> None:
        """Drain readers before snapshot to reduce partial-history races."""
        if self._raw_reader is None and self._pre_reader is None and self._result_reader is None:
            return
        try:
            start_raw_count = len(self._raw_history)
            start_pre_count = len(self._pre_history)
            start_result_count = len(self._result_history)
            deadline = time.monotonic() + 0.8

            while True:
                progress = False

                if self._raw_reader is not None:
                    for _ in range(self._max_pop_per_snapshot_drain):
                        collection = self._raw_reader.pop_raw_collection()
                        if collection is None:
                            break
                        self._raw_history.append(collection)
                        progress = True

                if self._pre_reader is not None:
                    for _ in range(self._max_pop_per_snapshot_drain):
                        collection = self._pre_reader.pop_preprocessed_collection()
                        if collection is None:
                            break
                        self._pre_history.append(collection)
                        progress = True

                if self._result_reader is not None:
                    for _ in range(self._max_pop_per_snapshot_drain):
                        collection = self._result_reader.pop_result_collection()
                        if collection is None:
                            break
                        self._record_result_history(collection)
                        progress = True

                if progress:
                    continue

                missing_raw = self._raw_reader is not None and len(self._raw_history) == start_raw_count
                missing_pre = self._pre_reader is not None and len(self._pre_history) == start_pre_count
                got_results = len(self._result_history) > start_result_count

                if got_results and (missing_raw or missing_pre) and time.monotonic() < deadline:
                    time.sleep(0.01)
                    continue
                break
        except Exception as exc:  # noqa: BLE001
            self._log(f"Snapshot drain warning: {exc}")

    def _drop_pending_ring_payloads(self, *, include_results: bool = True) -> None:
        """Drop unread payloads from active readers."""
        dropped_raw = self._raw_reader.drop_all() if self._raw_reader is not None else 0
        dropped_pre = self._pre_reader.drop_all() if self._pre_reader is not None else 0
        dropped_results = 0
        if include_results and self._result_reader is not None:
            dropped_results = self._result_reader.drop_all()

        if dropped_raw or dropped_pre or dropped_results:
            self._log(
                "Single capture ring reset: "
                f"dropped raw={dropped_raw}, "
                f"preprocessed={dropped_pre}, "
                f"results={dropped_results}"
            )