import enum
from datetime import datetime, timezone

from sqlalchemy import Enum, ForeignKey, Index, Integer, String, Text, Boolean, DateTime, UniqueConstraint
from sqlalchemy.orm import Mapped, mapped_column, relationship

from .database import Base


class Priority(str, enum.Enum):
    critical = "critical"
    high = "high"
    medium = "medium"
    low = "low"


class Status(str, enum.Enum):
    idea = "idea"
    draft = "draft"
    todo = "todo"
    in_progress = "in_progress"
    done = "done"


class NodeType(str, enum.Enum):
    pillar = "pillar"
    requirement = "requirement"
    sub_requirement = "sub_requirement"
    leaf = "leaf"
    planning = "planning"


class CodeLanguage(str, enum.Enum):
    python = "python"
    cpp = "cpp"
    typescript = "typescript"


class TestStatus(str, enum.Enum):
    not_written = "not_written"
    written = "written"
    passing = "passing"
    failing = "failing"


def _utcnow():
    return datetime.now(timezone.utc)


class RequirementNode(Base):
    __tablename__ = "requirement_nodes"

    id: Mapped[str] = mapped_column(String(64), primary_key=True)
    title: Mapped[str] = mapped_column(String(256), nullable=False)
    description: Mapped[str | None] = mapped_column(Text, nullable=True)
    priority: Mapped[Priority] = mapped_column(Enum(Priority), default=Priority.medium)
    phase: Mapped[int | None] = mapped_column(Integer, nullable=True)
    status: Mapped[Status] = mapped_column(Enum(Status), default=Status.draft)
    node_type: Mapped[NodeType] = mapped_column(Enum(NodeType), default=NodeType.requirement)
    parent_id: Mapped[str | None] = mapped_column(
        String(64), ForeignKey("requirement_nodes.id", ondelete="CASCADE"), nullable=True
    )
    sort_order: Mapped[int] = mapped_column(Integer, default=0)
    project_id: Mapped[int | None] = mapped_column(
        Integer, ForeignKey("projects.id", ondelete="CASCADE"), nullable=True
    )

    # Quality gate flags
    traceable: Mapped[bool] = mapped_column(Boolean, default=False)
    measurable: Mapped[bool] = mapped_column(Boolean, default=False)
    consistent: Mapped[bool] = mapped_column(Boolean, default=False)
    single_purpose: Mapped[bool] = mapped_column(Boolean, default=False)

    # Issue tracker integration
    gitea_issue_number: Mapped[int | None] = mapped_column(Integer, nullable=True)
    gitea_repo: Mapped[str | None] = mapped_column(String(256), nullable=True)

    # Acceptance criteria and code (all node types)
    acceptance_criteria: Mapped[str | None] = mapped_column(Text, nullable=True)
    test_spec: Mapped[str | None] = mapped_column(Text, nullable=True)
    test_code: Mapped[str | None] = mapped_column(Text, nullable=True)
    impl_code: Mapped[str | None] = mapped_column(Text, nullable=True)
    code_language: Mapped[CodeLanguage | None] = mapped_column(
        Enum(CodeLanguage), nullable=True
    )
    target_test_file: Mapped[str | None] = mapped_column(String(512), nullable=True)
    target_impl_file: Mapped[str | None] = mapped_column(String(512), nullable=True)
    test_status: Mapped[TestStatus] = mapped_column(
        Enum(TestStatus), default=TestStatus.not_written
    )

    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_utcnow)
    updated_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), default=_utcnow, onupdate=_utcnow
    )

    # Relationships
    parent: Mapped["RequirementNode | None"] = relationship(
        "RequirementNode", remote_side="RequirementNode.id", back_populates="children"
    )
    children: Mapped[list["RequirementNode"]] = relationship(
        "RequirementNode", back_populates="parent", cascade="all, delete-orphan",
        order_by="RequirementNode.sort_order"
    )
    project: Mapped["Project | None"] = relationship("Project", back_populates="requirements")

    # Cross-pillar links (outgoing)
    outgoing_links: Mapped[list["CrossPillarLink"]] = relationship(
        "CrossPillarLink", foreign_keys="CrossPillarLink.source_id",
        back_populates="source", cascade="all, delete-orphan"
    )
    incoming_links: Mapped[list["CrossPillarLink"]] = relationship(
        "CrossPillarLink", foreign_keys="CrossPillarLink.target_id",
        back_populates="target", cascade="all, delete-orphan"
    )
    history: Mapped[list["RequirementHistory"]] = relationship(
        "RequirementHistory", back_populates="requirement",
        cascade="all, delete-orphan", order_by="RequirementHistory.version"
    )


class CrossPillarLink(Base):
    __tablename__ = "cross_pillar_links"

    source_id: Mapped[str] = mapped_column(
        String(64), ForeignKey("requirement_nodes.id", ondelete="CASCADE"), primary_key=True
    )
    target_id: Mapped[str] = mapped_column(
        String(64), ForeignKey("requirement_nodes.id", ondelete="CASCADE"), primary_key=True
    )
    relationship_type: Mapped[str] = mapped_column(
        String(64), default="shared_parent"
    )

    source: Mapped[RequirementNode] = relationship(
        "RequirementNode", foreign_keys=[source_id], back_populates="outgoing_links"
    )
    target: Mapped[RequirementNode] = relationship(
        "RequirementNode", foreign_keys=[target_id], back_populates="incoming_links"
    )


class Project(Base):
    __tablename__ = "projects"

    id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
    name: Mapped[str] = mapped_column(String(256), nullable=False)
    description: Mapped[str | None] = mapped_column(Text, nullable=True)
    repo_path: Mapped[str | None] = mapped_column(String(512), nullable=True)
    repo_url: Mapped[str | None] = mapped_column(String(512), nullable=True)
    requirements_yaml_path: Mapped[str | None] = mapped_column(String(512), nullable=True)
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_utcnow)

    requirements: Mapped[list[RequirementNode]] = relationship(
        "RequirementNode", back_populates="project", cascade="all, delete-orphan"
    )
    layouts: Mapped[list["GraphLayout"]] = relationship(
        "GraphLayout", back_populates="project", cascade="all, delete-orphan"
    )


class RequirementHistory(Base):
    __tablename__ = "requirement_history"
    __table_args__ = (
        UniqueConstraint("requirement_id", "version", name="uq_requirement_version"),
        Index("idx_req_history_req_version", "requirement_id", "version"),
    )

    id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
    requirement_id: Mapped[str] = mapped_column(
        String(64), ForeignKey("requirement_nodes.id", ondelete="CASCADE"), nullable=False
    )
    version: Mapped[int] = mapped_column(Integer, nullable=False)

    # Snapshot of editable fields
    title: Mapped[str] = mapped_column(String(256), nullable=False)
    description: Mapped[str | None] = mapped_column(Text, nullable=True)
    priority: Mapped[str] = mapped_column(String(16), nullable=False)
    phase: Mapped[int | None] = mapped_column(Integer, nullable=True)
    status: Mapped[str] = mapped_column(String(16), nullable=False)
    node_type: Mapped[str] = mapped_column(String(32), nullable=False)
    acceptance_criteria: Mapped[str | None] = mapped_column(Text, nullable=True)
    test_spec: Mapped[str | None] = mapped_column(Text, nullable=True)
    test_code: Mapped[str | None] = mapped_column(Text, nullable=True)
    impl_code: Mapped[str | None] = mapped_column(Text, nullable=True)
    code_language: Mapped[str | None] = mapped_column(String(16), nullable=True)
    target_test_file: Mapped[str | None] = mapped_column(String(512), nullable=True)
    target_impl_file: Mapped[str | None] = mapped_column(String(512), nullable=True)
    measurable: Mapped[bool] = mapped_column(Boolean, default=False)
    consistent: Mapped[bool] = mapped_column(Boolean, default=False)
    single_purpose: Mapped[bool] = mapped_column(Boolean, default=False)
    gitea_issue_number: Mapped[int | None] = mapped_column(Integer, nullable=True)
    gitea_repo: Mapped[str | None] = mapped_column(String(256), nullable=True)

    # Metadata
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_utcnow)
    change_summary: Mapped[str | None] = mapped_column(String(512), nullable=True)

    requirement: Mapped[RequirementNode] = relationship(
        "RequirementNode", back_populates="history"
    )


class GraphLayout(Base):
    __tablename__ = "graph_layouts"

    id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
    name: Mapped[str] = mapped_column(String(128), nullable=False)
    description: Mapped[str | None] = mapped_column(String(512), nullable=True)
    project_id: Mapped[int | None] = mapped_column(
        Integer, ForeignKey("projects.id", ondelete="CASCADE"), nullable=True
    )
    node_positions: Mapped[str] = mapped_column(Text, nullable=False)
    viewport: Mapped[str] = mapped_column(Text, nullable=False)
    is_default: Mapped[bool] = mapped_column(Boolean, default=False)
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_utcnow)
    updated_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), default=_utcnow, onupdate=_utcnow
    )

    project: Mapped["Project | None"] = relationship("Project", back_populates="layouts")