from datetime import date, datetime

from sqlalchemy import (
    BigInteger,
    Boolean,
    Date,
    DateTime,
    Float,
    ForeignKey,
    Integer,
    JSON,
    String,
    Text,
    UniqueConstraint,
    func,
)
from sqlalchemy.orm import Mapped, mapped_column, relationship

from app.db import Base


class User(Base):
    __tablename__ = "users"

    id: Mapped[int] = mapped_column(primary_key=True)
    google_sub: Mapped[str] = mapped_column(String(64), unique=True, index=True)
    email: Mapped[str] = mapped_column(String(320), unique=True, index=True)
    display_name: Mapped[str | None] = mapped_column(String(255))
    avatar_url: Mapped[str | None] = mapped_column(String(1024))
    role: Mapped[str] = mapped_column(String(16), default="user", server_default="user")
    # Free-form UI preferences (theme, color scheme, font scale, default filters…).
    preferences: Mapped[dict | None] = mapped_column(JSON)
    created_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), server_default=func.now()
    )

    token: Mapped["OAuthToken | None"] = relationship(
        back_populates="user", uselist=False, cascade="all, delete-orphan"
    )
    subscriptions: Mapped[list["Subscription"]] = relationship(
        back_populates="user", cascade="all, delete-orphan"
    )


class OAuthToken(Base):
    __tablename__ = "oauth_tokens"

    id: Mapped[int] = mapped_column(primary_key=True)
    user_id: Mapped[int] = mapped_column(
        ForeignKey("users.id", ondelete="CASCADE"), unique=True
    )
    # Refresh token encrypted at rest (Fernet). Access token is short-lived and low risk.
    refresh_token_enc: Mapped[str | None] = mapped_column(String)
    access_token: Mapped[str | None] = mapped_column(String)
    expiry: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
    scopes: Mapped[str | None] = mapped_column(String)
    updated_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), server_default=func.now(), onupdate=func.now()
    )

    user: Mapped["User"] = relationship(back_populates="token")


class Channel(Base):
    """A YouTube channel. Shared across all users (one channel's videos are the same
    for everyone), so its expensive metadata is fetched and stored only once."""

    __tablename__ = "channels"

    id: Mapped[str] = mapped_column(String(32), primary_key=True)  # "UC..." channel id
    title: Mapped[str | None] = mapped_column(String(255))
    handle: Mapped[str | None] = mapped_column(String(255))
    description: Mapped[str | None] = mapped_column(Text)
    thumbnail_url: Mapped[str | None] = mapped_column(String(1024))
    uploads_playlist_id: Mapped[str | None] = mapped_column(String(64))
    subscriber_count: Mapped[int | None] = mapped_column(BigInteger)
    video_count: Mapped[int | None] = mapped_column(BigInteger)
    topic_categories: Mapped[list | None] = mapped_column(JSON)
    default_language: Mapped[str | None] = mapped_column(String(16))
    country: Mapped[str | None] = mapped_column(String(8))

    # Sync bookkeeping.
    details_synced_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
    recent_synced_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
    last_rss_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
    backfill_cursor: Mapped[str | None] = mapped_column(String(128))
    backfill_done: Mapped[bool] = mapped_column(
        Boolean, default=False, server_default="false"
    )
    created_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), server_default=func.now()
    )

    videos: Mapped[list["Video"]] = relationship(back_populates="channel")
    subscriptions: Mapped[list["Subscription"]] = relationship(back_populates="channel")


class Subscription(Base):
    """Per-user link to a channel, with the user's own priority/visibility overrides."""

    __tablename__ = "subscriptions"
    __table_args__ = (UniqueConstraint("user_id", "channel_id", name="uq_user_channel"),)

    id: Mapped[int] = mapped_column(primary_key=True)
    user_id: Mapped[int] = mapped_column(
        ForeignKey("users.id", ondelete="CASCADE"), index=True
    )
    channel_id: Mapped[str] = mapped_column(
        ForeignKey("channels.id", ondelete="CASCADE"), index=True
    )
    # YouTube's subscription resource id, needed to unsubscribe via the API.
    yt_subscription_id: Mapped[str | None] = mapped_column(String(128))
    priority: Mapped[int] = mapped_column(Integer, default=0, server_default="0")
    hidden: Mapped[bool] = mapped_column(Boolean, default=False, server_default="false")
    subscribed_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
    created_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), server_default=func.now()
    )

    user: Mapped["User"] = relationship(back_populates="subscriptions")
    channel: Mapped["Channel"] = relationship(back_populates="subscriptions")


class Video(Base):
    """A YouTube video. Shared across users; per-user state lives elsewhere."""

    __tablename__ = "videos"

    id: Mapped[str] = mapped_column(String(16), primary_key=True)  # video id
    channel_id: Mapped[str] = mapped_column(
        ForeignKey("channels.id", ondelete="CASCADE"), index=True
    )
    title: Mapped[str | None] = mapped_column(Text)
    description: Mapped[str | None] = mapped_column(Text)
    published_at: Mapped[datetime | None] = mapped_column(
        DateTime(timezone=True), index=True
    )
    thumbnail_url: Mapped[str | None] = mapped_column(String(1024))
    duration_seconds: Mapped[int | None] = mapped_column(Integer)
    view_count: Mapped[int | None] = mapped_column(BigInteger)
    like_count: Mapped[int | None] = mapped_column(BigInteger)
    category_id: Mapped[int | None] = mapped_column(Integer)
    topic_categories: Mapped[list | None] = mapped_column(JSON)
    default_language: Mapped[str | None] = mapped_column(String(16))
    detected_language: Mapped[str | None] = mapped_column(String(16))
    is_short: Mapped[bool] = mapped_column(
        Boolean, default=False, server_default="false", index=True
    )
    # Whether the youtube.com/shorts/<id> probe has run for this video.
    shorts_probed: Mapped[bool] = mapped_column(
        Boolean, default=False, server_default="false", index=True
    )
    # none | live | upcoming | premiere | was_live
    live_status: Mapped[str] = mapped_column(
        String(16), default="none", server_default="none", index=True
    )
    enriched_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
    created_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), server_default=func.now()
    )

    channel: Mapped["Channel"] = relationship(back_populates="videos")


class Tag(Base):
    """A label. System tags (user_id NULL) are computed automatically and shared by all
    users; user tags (user_id set) are personal. category groups them in the UI."""

    __tablename__ = "tags"

    id: Mapped[int] = mapped_column(primary_key=True)
    user_id: Mapped[int | None] = mapped_column(
        ForeignKey("users.id", ondelete="CASCADE"), index=True
    )
    name: Mapped[str] = mapped_column(String(64))
    color: Mapped[str | None] = mapped_column(String(16))
    # language | topic | other
    category: Mapped[str] = mapped_column(
        String(16), default="other", server_default="other"
    )
    created_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), server_default=func.now()
    )


class ChannelTag(Base):
    """Links a tag to a channel. source='auto' rows are managed by the auto-tagger and
    regenerated freely; source='user' rows are never touched by the system."""

    __tablename__ = "channel_tags"
    __table_args__ = (
        UniqueConstraint("channel_id", "tag_id", "user_id", name="uq_channel_tag"),
    )

    id: Mapped[int] = mapped_column(primary_key=True)
    channel_id: Mapped[str] = mapped_column(
        ForeignKey("channels.id", ondelete="CASCADE"), index=True
    )
    tag_id: Mapped[int] = mapped_column(
        ForeignKey("tags.id", ondelete="CASCADE"), index=True
    )
    # NULL = system/auto link visible to everyone; set = a specific user's link.
    user_id: Mapped[int | None] = mapped_column(
        ForeignKey("users.id", ondelete="CASCADE")
    )
    source: Mapped[str] = mapped_column(String(8), default="auto", server_default="auto")
    confidence: Mapped[float | None] = mapped_column(Float)


class VideoState(Base):
    """Per-user watch state for a video. Rows exist only for non-default states; the
    absence of a row means 'new/unseen'."""

    __tablename__ = "video_states"
    __table_args__ = (UniqueConstraint("user_id", "video_id", name="uq_user_video"),)

    id: Mapped[int] = mapped_column(primary_key=True)
    user_id: Mapped[int] = mapped_column(
        ForeignKey("users.id", ondelete="CASCADE"), index=True
    )
    video_id: Mapped[str] = mapped_column(
        ForeignKey("videos.id", ondelete="CASCADE"), index=True
    )
    # new | watched | saved | hidden
    status: Mapped[str] = mapped_column(String(12), default="new", server_default="new")
    watched_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
    updated_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), server_default=func.now(), onupdate=func.now()
    )


class ApiQuotaUsage(Base):
    """Tracks YouTube Data API units spent per Pacific-time day (the quota resets at
    midnight Pacific). The whole app shares one daily budget."""

    __tablename__ = "api_quota_usage"

    day: Mapped[date] = mapped_column(Date, primary_key=True)
    units_used: Mapped[int] = mapped_column(Integer, default=0, server_default="0")