LLeMbas/src/lembas/db/models/library.py

"""What the model can reach for: knowledge, notes, memory and skills.

Four stores rather than one, because they differ in the two ways that matter --
who writes a record, and how a record reaches the model:

* **Document** is uploaded by a person and searched by the model. It is the
  only one holding a file, and it is deliberately shaped like ``Attachment``:
  both come out of ``services.files.prepare`` and carry the same processed
  content.
* **Note** is written by the model and edited by a person. Long enough that it
  has to be searched rather than injected.
* **Memory** is one short fact, and *is* injected -- every one of them, every
  turn, up to a budget. Anything that would not survive that treatment belongs
  in a note.
* **Skill** is a named instruction document. Its description is injected so the
  model knows the skill exists; the body is fetched only when it decides to use
  it, which is what keeps a hundred skills affordable.

Everything except Memory can be shared -- see ``Share`` below and
``services.sharing``. Memory cannot: a record about a person is not content to
hand round, and "share my memories with the team" is a question nobody asked.
"""

from __future__ import annotations

from sqlalchemy import (
    Boolean,
    Column,
    ForeignKey,
    Index,
    Integer,
    String,
    Table,
    Text,
    UniqueConstraint,
)
from sqlalchemy.orm import Mapped, mapped_column, relationship

from lembas.db.base import Base, Timestamps, UUIDPrimaryKey

# Who wrote a record. Not decoration: a skill the model wrote itself is the one
# worth looking at twice when its behaviour changes unexpectedly.
AUTHOR_USER = "user"
AUTHOR_MODEL = "model"

# Where a document came from.
SOURCE_UPLOAD = "upload"
SOURCE_LINK = "link"

# Resource kinds that can be shared. Values are stored, so they are part of the
# schema rather than an implementation detail.
RESOURCE_BASE = "base"
RESOURCE_NOTE = "note"
RESOURCE_SKILL = "skill"

PRINCIPAL_USER = "user"
PRINCIPAL_GROUP = "group"

# Which knowledge bases a chat draws on. A chat with none searches everything
# its owner can see; a chat with some is scoped to those, which is the point --
# "answer from the contract folder" is a different question from "answer from
# everything I have ever uploaded".
chat_knowledge_bases = Table(
    "chat_knowledge_bases",
    Base.metadata,
    Column("chat_id", String(32), ForeignKey("chats.id", ondelete="CASCADE"), primary_key=True),
    Column(
        "base_id",
        String(32),
        ForeignKey("knowledge_bases.id", ondelete="CASCADE"),
        primary_key=True,
    ),
)


class KnowledgeBase(UUIDPrimaryKey, Timestamps, Base):
    """A named collection of documents.

    Sharing lives here rather than on the individual document: "this folder is
    the team's" is the granularity people actually think in, and per-document
    grants would mean answering "who can see this?" by checking every file.
    A document is visible to whoever can see the base it is in.
    """

    __tablename__ = "knowledge_bases"
    __table_args__ = (UniqueConstraint("owner_id", "name"),)

    owner_id: Mapped[str] = mapped_column(
        String(32), ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    name: Mapped[str] = mapped_column(String(200), nullable=False)
    description: Mapped[str] = mapped_column(Text, default="")

    documents: Mapped[list[Document]] = relationship(
        back_populates="base", cascade="all, delete-orphan"
    )

    def __repr__(self) -> str:
        return f"<KnowledgeBase {self.name!r}>"


class Document(UUIDPrimaryKey, Timestamps, Base):
    """One item in a knowledge library: a file, an image or a saved web page.

    The content columns mirror ``Attachment`` exactly because both are produced
    by ``services.files.prepare`` -- images downscaled, PDF text extracted once,
    type decided by sniffing bytes. Keeping the shapes identical is what lets a
    document be attached to a message by copying rather than converting.
    """

    __tablename__ = "documents"

    owner_id: Mapped[str] = mapped_column(
        String(32), ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    # Nullable only so the column could be added to an existing table. The
    # service always sets it, and a startup sweep files anything that predates
    # bases into its owner's default -- see documents.sweep_unfiled.
    base_id: Mapped[str | None] = mapped_column(
        String(32), ForeignKey("knowledge_bases.id", ondelete="CASCADE"), index=True
    )

    title: Mapped[str] = mapped_column(String(300), nullable=False)
    description: Mapped[str] = mapped_column(Text, default="")

    source: Mapped[str] = mapped_column(String(16), default=SOURCE_UPLOAD, nullable=False)
    # Set for a saved web page, so it can be re-fetched and cited.
    source_url: Mapped[str] = mapped_column(Text, default="")

    # --- The same content columns as Attachment ---
    filename: Mapped[str] = mapped_column(String(300), default="")
    stored_name: Mapped[str] = mapped_column(String(120), default="")
    media_type: Mapped[str] = mapped_column(String(100), default="")
    size_bytes: Mapped[int] = mapped_column(Integer, default=0, nullable=False)
    kind: Mapped[str] = mapped_column(String(16), default="text", nullable=False)
    width: Mapped[int] = mapped_column(Integer, default=0, nullable=False)
    height: Mapped[int] = mapped_column(Integer, default=0, nullable=False)
    extracted_text: Mapped[str] = mapped_column(Text, default="")
    pages: Mapped[int] = mapped_column(Integer, default=0, nullable=False)
    truncated: Mapped[bool] = mapped_column(Boolean, default=False, nullable=False)
    extraction_error: Mapped[str] = mapped_column(Text, default="")

    base: Mapped[KnowledgeBase] = relationship(back_populates="documents")

    @property
    def is_image(self) -> bool:
        return self.kind == "image"

    @property
    def human_size(self) -> str:
        size = float(self.size_bytes)
        for unit in ("B", "KB", "MB"):
            if size < 1024 or unit == "MB":
                return f"{size:.0f} {unit}" if unit == "B" else f"{size:.1f} {unit}"
            size /= 1024
        return f"{size:.1f} MB"

    def __repr__(self) -> str:
        return f"<Document {self.title!r}>"


class Note(UUIDPrimaryKey, Timestamps, Base):
    """Something the model wrote down, or a person did.

    Longer and more specific than a memory. Not injected: a handful of notes
    would fill a context window on their own, so the model searches for the one
    it needs.
    """

    __tablename__ = "notes"

    owner_id: Mapped[str] = mapped_column(
        String(32), ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    title: Mapped[str] = mapped_column(String(300), nullable=False)
    body: Mapped[str] = mapped_column(Text, default="")
    author: Mapped[str] = mapped_column(String(16), default=AUTHOR_USER, nullable=False)

    def __repr__(self) -> str:
        return f"<Note {self.title!r}>"


class Memory(UUIDPrimaryKey, Timestamps, Base):
    """One short fact, in front of the model on every turn.

    Deliberately not shareable and deliberately small. The length cap is
    enforced in the service rather than by the column, so an over-long write
    from a tool is trimmed with an explanation instead of failing the turn.
    """

    __tablename__ = "memories"

    owner_id: Mapped[str] = mapped_column(
        String(32), ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    content: Mapped[str] = mapped_column(Text, nullable=False)
    author: Mapped[str] = mapped_column(String(16), default=AUTHOR_MODEL, nullable=False)

    def __repr__(self) -> str:
        return f"<Memory {self.content[:40]!r}>"


class Skill(UUIDPrimaryKey, Timestamps, Base):
    """A named set of instructions the model can choose to follow.

    `description` is the load-bearing field: it is what gets injected, and it is
    the only thing the model has to decide whether the skill is relevant. The
    body is fetched with a tool.
    """

    __tablename__ = "skills"
    __table_args__ = (UniqueConstraint("owner_id", "name"),)

    owner_id: Mapped[str] = mapped_column(
        String(32), ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    # Slug, referenced by the model when it asks for the body.
    name: Mapped[str] = mapped_column(String(120), nullable=False)
    description: Mapped[str] = mapped_column(Text, default="")
    body: Mapped[str] = mapped_column(Text, default="")
    enabled: Mapped[bool] = mapped_column(Boolean, default=True, nullable=False)
    author: Mapped[str] = mapped_column(String(16), default=AUTHOR_USER, nullable=False)

    revisions: Mapped[list[SkillRevision]] = relationship(
        back_populates="skill",
        cascade="all, delete-orphan",
        order_by="SkillRevision.created_at.desc()",
    )

    def __repr__(self) -> str:
        return f"<Skill {self.name}>"


class SkillRevision(UUIDPrimaryKey, Timestamps, Base):
    """The state of a skill before a change.

    A model may rewrite its own skills, so every write snapshots what was there
    first. That is the whole safety story for self-modification: not a gate, but
    a record and a way back.
    """

    __tablename__ = "skill_revisions"

    skill_id: Mapped[str] = mapped_column(
        String(32), ForeignKey("skills.id", ondelete="CASCADE"), nullable=False, index=True
    )
    description: Mapped[str] = mapped_column(Text, default="")
    body: Mapped[str] = mapped_column(Text, default="")
    # Who made the change this revision is the "before" of.
    author: Mapped[str] = mapped_column(String(16), default=AUTHOR_USER, nullable=False)
    note: Mapped[str] = mapped_column(String(200), default="")

    skill: Mapped[Skill] = relationship(back_populates="revisions")


class Share(UUIDPrimaryKey, Timestamps, Base):
    """One grant of access to one resource.

    A single table across documents, notes and skills rather than three
    association tables, because the rule is identical in all three cases and
    ``services.sharing`` is the only thing that reads it.

    A grant, never a denial -- the same principle as group permissions. Somebody
    who cannot see a resource simply has no row here.
    """

    __tablename__ = "shares"
    __table_args__ = (
        UniqueConstraint(
            "resource_type", "resource_id", "principal_type", "principal_id"
        ),
    )

    resource_type: Mapped[str] = mapped_column(String(16), nullable=False)
    resource_id: Mapped[str] = mapped_column(String(32), nullable=False)

    principal_type: Mapped[str] = mapped_column(String(16), nullable=False)
    # No foreign key: this column points at users or groups depending on
    # principal_type, and SQLite cannot express that. services.sharing deletes
    # dangling rows when a user or group goes.
    principal_id: Mapped[str] = mapped_column(String(32), nullable=False)

    def __repr__(self) -> str:
        return f"<Share {self.resource_type}:{self.resource_id} -> {self.principal_type}>"


Index("ix_shares_resource", Share.resource_type, Share.resource_id)
Index("ix_shares_principal", Share.principal_type, Share.principal_id)