"""ProductionRun and ProductionEvent models.

A production run is what an operator opens when production starts and a supervisor
closes when it ends. It is the thing that outlives a page: before this, the timer,
the cycle count and the "production started" flag were Alpine variables in
task_execute.html, and navigating between tasks - a full page load - destroyed them.

The measurement deadline is stored as an absolute timestamp (next_measurement_at)
rather than a remaining count. Any client can then derive the countdown from it, get
the same answer, survive a reload, and tell how far *past* the interval it is by
letting the difference go negative.

With one station app installed per PC (see the install architecture of 28/07) the
database is the only place this state can live: the API keeps nothing in process
memory.
"""
from datetime import datetime
from typing import TYPE_CHECKING, Optional

from sqlalchemy import (
    DateTime, Enum, ForeignKey, Index, Integer, SmallInteger, String, Text,
    UniqueConstraint, func,
)
from sqlalchemy.orm import Mapped, mapped_column, relationship

from src.backend.database import Base

if TYPE_CHECKING:
    from src.backend.models.orm.recipe import Recipe, RecipeVersion
    from src.backend.models.orm.station import Station


RUN_STATUSES = ("running", "paused", "closed")
# task_measured marks a measurement task finished inside a cycle that is not over
# yet; only the last one produces cycle_completed and restarts the interval.
# remeasure is the piece being turned and measured again without closing the cycle.
EVENT_TYPES = (
    "start", "cycle_completed", "task_measured", "remeasure",
    "line_stop", "resume", "close",
)


class ProductionRun(Base):
    __tablename__ = "production_runs"

    id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)

    station_id: Mapped[int] = mapped_column(
        Integer, ForeignKey("stations.id"), nullable=False, index=True
    )
    recipe_id: Mapped[int] = mapped_column(
        Integer, ForeignKey("recipes.id"), nullable=False, index=True
    )
    version_id: Mapped[int] = mapped_column(
        Integer, ForeignKey("recipe_versions.id"), nullable=False, index=True
    )
    operator_id: Mapped[int] = mapped_column(
        Integer, ForeignKey("users.id"), nullable=False, index=True
    )

    # Traceability travels with the run instead of the Flask session, so it stays
    # attached to every measurement taken during it.
    lot_number: Mapped[Optional[str]] = mapped_column(String(100), nullable=True, index=True)
    serial_number: Mapped[Optional[str]] = mapped_column(String(100), nullable=True, index=True)

    status: Mapped[str] = mapped_column(
        Enum(*RUN_STATUSES, name="production_run_status_enum"),
        nullable=False,
        default="running",
        index=True,
    )

    # Snapshot of the recipe interval at start: editing the recipe mid-run must not
    # move the deadline of a production already under way.
    measurement_interval_minutes: Mapped[Optional[int]] = mapped_column(
        SmallInteger, nullable=True
    )
    # When the next measurement falls due. Null when the recipe has no interval.
    # Past this instant the run is overdue, and by how much is simply now - this.
    next_measurement_at: Mapped[Optional[datetime]] = mapped_column(
        DateTime, nullable=True, index=True
    )
    cycle_count: Mapped[int] = mapped_column(Integer, nullable=False, default=0)

    started_at: Mapped[datetime] = mapped_column(
        DateTime, nullable=False, server_default=func.now()
    )
    paused_at: Mapped[Optional[datetime]] = mapped_column(DateTime, nullable=True)
    closed_at: Mapped[Optional[datetime]] = mapped_column(DateTime, nullable=True)
    closed_by: Mapped[Optional[int]] = mapped_column(
        Integer, ForeignKey("users.id"), nullable=True
    )
    # Statistics file emitted when the run was closed, relative to the upload dir.
    statistics_path: Mapped[Optional[str]] = mapped_column(String(500), nullable=True)

    # Mirrors station_id while the run is open and goes NULL when it closes. A unique
    # index on it lets the database - not a check-then-insert race - guarantee that a
    # station never has two open runs. Repeated NULLs do not collide in a unique index.
    active_station_id: Mapped[Optional[int]] = mapped_column(Integer, nullable=True)

    station: Mapped["Station"] = relationship(lazy="selectin")
    recipe: Mapped["Recipe"] = relationship(lazy="selectin")
    version: Mapped["RecipeVersion"] = relationship(lazy="selectin")
    events: Mapped[list["ProductionEvent"]] = relationship(
        back_populates="run",
        cascade="all, delete-orphan",
        order_by="ProductionEvent.created_at",
    )

    __table_args__ = (
        UniqueConstraint("active_station_id", name="uq_production_runs_active_station"),
        Index("ix_production_runs_station_status", "station_id", "status"),
        {"mysql_engine": "InnoDB", "mysql_charset": "utf8mb4"},
    )

    @property
    def is_open(self) -> bool:
        return self.status in ("running", "paused")

    def __repr__(self) -> str:
        return f"<ProductionRun {self.id} station={self.station_id} {self.status}>"


class ProductionEvent(Base):
    """Append-only trace of what happened during a run.

    This is the record that did not exist before: without it there is no history of
    a production, and nothing for the statistics file or the ERP hand-off to stand on.
    """

    __tablename__ = "production_events"

    id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
    run_id: Mapped[int] = mapped_column(
        Integer, ForeignKey("production_runs.id", ondelete="CASCADE"),
        nullable=False, index=True,
    )
    event_type: Mapped[str] = mapped_column(
        Enum(*EVENT_TYPES, name="production_event_type_enum"), nullable=False, index=True
    )
    user_id: Mapped[int] = mapped_column(
        Integer, ForeignKey("users.id"), nullable=False, index=True
    )
    # Who authorised it, when the action needed a supervisor (fermo linea, chiusura).
    supervisor_id: Mapped[Optional[int]] = mapped_column(
        Integer, ForeignKey("users.id"), nullable=True
    )
    # Which task the event is about, for the ones that happen inside a cycle. A
    # task_measured or a remeasure that does not say which task is not a record of
    # anything; null for the events that concern the run as a whole.
    task_id: Mapped[Optional[int]] = mapped_column(
        Integer, ForeignKey("recipe_tasks.id"), nullable=True
    )
    note: Mapped[Optional[str]] = mapped_column(Text, nullable=True)
    created_at: Mapped[datetime] = mapped_column(
        DateTime, nullable=False, server_default=func.now(), index=True
    )

    run: Mapped["ProductionRun"] = relationship(back_populates="events")

    __table_args__ = (
        {"mysql_engine": "InnoDB", "mysql_charset": "utf8mb4"},
    )

    def __repr__(self) -> str:
        return f"<ProductionEvent run={self.run_id} {self.event_type}>"