import uuid
from datetime import datetime, timezone
from typing import Optional, Any, TYPE_CHECKING
from sqlalchemy import String, Text, DateTime, ForeignKey, Boolean, Integer, Index, CheckConstraint
from sqlalchemy.orm import Mapped, mapped_column, relationship
from sqlalchemy.dialects.postgresql import UUID, JSONB
from app.core.database import Base

if TYPE_CHECKING:
    from app.models.user import User
    from app.models.team import Team
    from app.models.account import Account
    from app.models.session import Session
    from app.models.category import TreeCategory
    from app.models.tag import TreeTag
    from app.models.folder import UserFolder
    from app.models.tree_share import TreeShare


class Tree(Base):
    __tablename__ = "trees"
    __table_args__ = (
        CheckConstraint(
            "visibility IN ('private', 'team', 'link', 'public')",
            name='ck_trees_visibility'
        ),
        CheckConstraint(
            "status IN ('draft', 'published')",
            name='ck_trees_status'
        ),
        CheckConstraint(
            "tree_type IN ('troubleshooting', 'procedural', 'maintenance')",
            name='ck_trees_tree_type'
        ),
    )

    id: Mapped[uuid.UUID] = mapped_column(
        UUID(as_uuid=True),
        primary_key=True,
        default=uuid.uuid4
    )
    name: Mapped[str] = mapped_column(String(255), nullable=False)
    description: Mapped[Optional[str]] = mapped_column(Text, nullable=True)
    # Legacy category field - kept for backward compatibility
    # New code should use category_id instead
    category: Mapped[Optional[str]] = mapped_column(String(100), nullable=True, index=True)
    # New category relationship
    category_id: Mapped[Optional[uuid.UUID]] = mapped_column(
        UUID(as_uuid=True),
        ForeignKey("tree_categories.id", ondelete="SET NULL"),
        nullable=True,
        index=True
    )
    tree_type: Mapped[str] = mapped_column(
        String(20),
        nullable=False,
        default='troubleshooting',
        server_default='troubleshooting',
        index=True,
        comment="Tree type: troubleshooting (branching decision tree) or procedural (linear step-by-step flow)"
    )
    tree_structure: Mapped[dict[str, Any]] = mapped_column(JSONB, nullable=False)
    intake_form: Mapped[Optional[list[dict[str, Any]]]] = mapped_column(
        JSONB,
        nullable=True,
        comment="Intake form field definitions for procedural flows (JSONB array)"
    )
    author_id: Mapped[Optional[uuid.UUID]] = mapped_column(
        UUID(as_uuid=True),
        ForeignKey("users.id"),
        nullable=True
    )
    team_id: Mapped[Optional[uuid.UUID]] = mapped_column(
        UUID(as_uuid=True),
        ForeignKey("teams.id"),
        nullable=True,
        index=True
    )
    account_id: Mapped[Optional[uuid.UUID]] = mapped_column(
        UUID(as_uuid=True),
        ForeignKey("accounts.id", ondelete="CASCADE"),
        nullable=True,
        index=True
    )
    is_active: Mapped[bool] = mapped_column(Boolean, default=True)
    is_public: Mapped[bool] = mapped_column(Boolean, default=False, index=True)
    is_default: Mapped[bool] = mapped_column(Boolean, default=False, index=True)
    visibility: Mapped[str] = mapped_column(
        String(20),
        nullable=False,
        default='team',
        index=True,
        comment="Visibility level: private (author only), team (account members), link (share token), public (all users)"
    )
    status: Mapped[str] = mapped_column(
        String(20),
        nullable=False,
        default='published',
        index=True,
        comment="Status: draft (work in progress) or published (validated and available)"
    )
    deleted_at: Mapped[Optional[datetime]] = mapped_column(
        DateTime(timezone=True),
        nullable=True,
        index=True
    )
    deleted_by: Mapped[Optional[uuid.UUID]] = mapped_column(
        UUID(as_uuid=True),
        ForeignKey("users.id"),
        nullable=True
    )
    version: Mapped[int] = mapped_column(Integer, default=1)
    created_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True),
        default=lambda: datetime.now(timezone.utc)
    )
    updated_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True),
        default=lambda: datetime.now(timezone.utc),
        onupdate=lambda: datetime.now(timezone.utc)
    )
    usage_count: Mapped[int] = mapped_column(Integer, default=0)
    # Fork tracking
    parent_tree_id: Mapped[Optional[uuid.UUID]] = mapped_column(
        UUID(as_uuid=True),
        ForeignKey("trees.id", ondelete="SET NULL"),
        nullable=True,
        index=True
    )
    fork_reason: Mapped[Optional[str]] = mapped_column(
        String(255),
        nullable=True,
        comment="Brief reason: 'Added Cisco Meraki steps for our network'"
    )
    parent_updated_at: Mapped[Optional[datetime]] = mapped_column(
        DateTime(timezone=True),
        nullable=True,
        comment="Snapshot of parent's updated_at when fork created. Compare to detect parent updates."
    )

    # Fork lineage tracking
    root_tree_id: Mapped[Optional[uuid.UUID]] = mapped_column(
        UUID(as_uuid=True),
        ForeignKey("trees.id", ondelete="SET NULL"),
        nullable=True,
        index=True,
        comment="Original tree at root of fork chain (NULL for non-forked trees)"
    )
    fork_depth: Mapped[int] = mapped_column(
        Integer,
        nullable=False,
        default=0,
        server_default="0",
        comment="Fork depth: 0 = original, 1 = direct fork, 2 = fork of fork, etc."
    )

    # Relationships
    author: Mapped[Optional["User"]] = relationship("User", foreign_keys=[author_id], back_populates="trees")
    team: Mapped[Optional["Team"]] = relationship("Team", back_populates="trees")
    account: Mapped[Optional["Account"]] = relationship("Account", foreign_keys=[account_id], back_populates="trees")

    # Fork relationships (self-referential)
    parent: Mapped[Optional["Tree"]] = relationship(
        "Tree",
        remote_side="Tree.id",
        foreign_keys=[parent_tree_id],
        back_populates="forks"
    )
    forks: Mapped[list["Tree"]] = relationship(
        "Tree",
        foreign_keys=[parent_tree_id],
        back_populates="parent"
    )
    root: Mapped[Optional["Tree"]] = relationship(
        "Tree",
        remote_side="Tree.id",
        foreign_keys=[root_tree_id]
    )
    sessions: Mapped[list["Session"]] = relationship("Session", back_populates="tree")
    shares: Mapped[list["TreeShare"]] = relationship(
        "TreeShare",
        back_populates="tree",
        cascade="all, delete-orphan"
    )

    # Organization relationships
    category_rel: Mapped[Optional["TreeCategory"]] = relationship("TreeCategory", back_populates="trees")
    tags: Mapped[list["TreeTag"]] = relationship(
        "TreeTag",
        secondary="tree_tag_assignments",
        back_populates="trees"
    )
    folders: Mapped[list["UserFolder"]] = relationship(
        "UserFolder",
        secondary="user_folder_trees",
        back_populates="trees"
    )

    # Full-text search index will be created in migration

    @property
    def tag_names(self) -> list[str]:
        """Returns list of tag names for this tree."""
        return [tag.name for tag in self.tags] if self.tags else []
