"""SQLAlchemy models (PostgreSQL 17 + pgvector).

Data model — see ``.agent/PLAN.md`` §Data Model:

* ``documents`` — one row per imported A9 file (full content, path, sha256 hash).
* ``chunks``    — retrieval units; each chunk points at its parent document
                  via ``document_id``. This is how an embedding maps back to
                  a document path (the "feed the whole document" requirement).
* ``query_log``     — observability: every question, its retrieval score,
                      the deflection decision, and latency.
* ``steering_notes`` — owner tuning notes injected into the system prompt
                      of every chat turn (phase 15, ``<tuning>`` section).
* ``kb_overview``    — single-row lite-generated outline of the KB's basic
                      categories, injected as the ``<knowledge_base>``
                      section of every chat turn (phase 31).
* ``git_sources``    — admin-managed source registry (git URLs + local
                      directories) the Sync button and import_docs
                      import (phase 35; ``kind`` discriminator added in
                      phase 38).
* ``saved_chats``    — owner-saved chat conversations: one row per
                      explicitly Saved conversation (auto-``title`` +
                      the ``bor.chat.v1`` message list as JSONB, phase
                      14 shape) — phase 50; ``/api/chat`` stays
                      stateless; ``share_token`` (NULL = private,
                      ``uuid4`` = publicly readable at
                      ``/shared/<token>``) — phase 51; ``sources_version``
                      (the KB generation the conversation was saved
                      against; 0 = the pre-counter KB, stale on the
                      first bump) — phase 53.
* ``sources_meta``   — single-row sources-version counter: which
                      generation of the knowledge base is current,
                      bumped exactly once per KB-changing sync so saved
                      chats can be marked stale (phase 53).
"""
from __future__ import annotations

import uuid
from datetime import datetime

from pgvector.sqlalchemy import Vector
from sqlalchemy import (
    Boolean,
    DateTime,
    Float,
    ForeignKey,
    Integer,
    String,
    Text,
    UniqueConstraint,
    func,
)
from sqlalchemy.dialects.postgresql import JSONB, UUID
from sqlalchemy.orm import Mapped, mapped_column, relationship

from app.config import get_settings
from app.db import Base

# Single source of truth for the vector column size (see .agent/PLAN.md A6).
EMBEDDING_DIM: int = get_settings().embedding_dim


class Document(Base):
    __tablename__ = "documents"
    __table_args__ = (UniqueConstraint("source", "path", name="uq_documents_source_path"),)

    id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
    source: Mapped[str] = mapped_column(String(120), index=True)  # e.g. "Homelab"
    path: Mapped[str] = mapped_column(String(1000), index=True)  # relative to source dir
    full_path: Mapped[str] = mapped_column(String(2000))  # absolute path at import time
    title: Mapped[str] = mapped_column(String(500))
    content: Mapped[str] = mapped_column(Text)  # full markdown — the RAG context
    content_hash: Mapped[str] = mapped_column(String(64), index=True)  # sha256 for change detection
    indexed_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), server_default=func.now())
    #: Lite-model summary, phase 30. Natural-language summary of the
    #: document (non-markdown A9 docs only, generated at import time by the
    #: aipi ``lite`` model). NULL for markdown docs, pre-phase-30 rows, and
    #: the fail-soft path where summary generation failed but the document
    #: was still indexed.
    summary: Mapped[str | None] = mapped_column(Text, default=None)

    chunks: Mapped[list[Chunk]] = relationship(
        back_populates="document", cascade="all, delete-orphan"
    )


class Chunk(Base):
    __tablename__ = "chunks"

    id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
    document_id: Mapped[uuid.UUID] = mapped_column(
        UUID(as_uuid=True), ForeignKey("documents.id", ondelete="CASCADE"), index=True
    )
    position: Mapped[int] = mapped_column(Integer)
    content: Mapped[str] = mapped_column(Text)
    embedding: Mapped[list[float] | None] = mapped_column(Vector(EMBEDDING_DIM))
    #: Summary chunk, position −1, phase 30. Marks the single extra embedded
    #: chunk mirroring ``Document.summary``; default False keeps every
    #: pre-phase-30 row (and ordinary content chunks) valid.
    is_summary: Mapped[bool] = mapped_column(Boolean, default=False)

    document: Mapped[Document] = relationship(back_populates="chunks")


class QueryLog(Base):
    __tablename__ = "query_log"

    id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
    question: Mapped[str] = mapped_column(Text)
    top_score: Mapped[float] = mapped_column(Float, default=0.0)  # best cosine similarity
    #: Lexical (FTS) candidates matched — the OR-tsquery hit count (A8). NULL
    #: for pre-hybrid rows (migration 0002).
    fts_hits: Mapped[int | None] = mapped_column(Integer)
    chunk_hits: Mapped[int] = mapped_column(Integer, default=0)
    deflected: Mapped[bool] = mapped_column(Boolean, default=False)  # True = honest "no idea"
    sources: Mapped[str] = mapped_column(Text, default="")  # comma-joined source paths
    latency_ms: Mapped[int] = mapped_column(Integer, default=0)
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), server_default=func.now())


class SteeringNote(Base):
    """One owner tuning instruction (phase 15).

    Notes are read into the system prompt of **every** chat turn as the
    ``<tuning>`` section (oldest first, char-budgeted — see
    :func:`app.rag.prompts.build_steering_section`).
    """

    __tablename__ = "steering_notes"

    id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
    note: Mapped[str] = mapped_column(Text)  # trimmed, 1–2000 chars (API-enforced)
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), server_default=func.now())


class KbOverview(Base):
    """Single-row, lite-generated outline of the knowledge base (phase 31).

    Exactly one row (``id = 1``, enforced by the migration 0005 server
    defaults) holds a plain-text outline of the KB's basic categories,
    generated by the aipi ``lite`` model whenever an import changes the KB.
    Chat turns only read this row (one indexed PK lookup) and inject it into
    the system prompt of every turn as the ``<knowledge_base>`` section — an
    empty row means the section is absent and the prompt stays
    byte-identical to the pre-phase text (phase 15 convention).
    """

    __tablename__ = "kb_overview"

    id: Mapped[int] = mapped_column(Integer, primary_key=True, server_default="1")
    content: Mapped[str] = mapped_column(Text, server_default="")  # the outline text
    updated_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), server_default=func.now()
    )


class SourcesMeta(Base):
    """Single-row sources-version counter (phase 53).

    Exactly one row (``id = 1``, seeded by migration 0010 — the
    ``kb_overview`` id=1 precedent) holds the current **generation** of
    the knowledge base. ``version`` is bumped exactly once per sync that
    actually changed the KB (phase 53, task 02 — change-gated on
    ``added + updated + pruned > 0``), so it doubles as the invalidation
    marker for saved chats: a ``saved_chats`` row stamped with an older
    generation is *stale* — its answers predate the current index and
    may be Regenerated against it (phase 53, tasks 03/05). The row is
    seeded by the migration (not lazily on first bump), so
    :func:`app.rag.sources_meta.current_sources_version` is a plain PK
    read.
    """

    __tablename__ = "sources_meta"

    id: Mapped[int] = mapped_column(Integer, primary_key=True, server_default="1")
    #: The KB generation. 0 = the pre-counter KB (everything indexed
    #: before phase 53); incremented by one per KB-changing sync.
    version: Mapped[int] = mapped_column(Integer, server_default="0")
    updated_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), server_default=func.now(), onupdate=func.now()
    )


class GitSource(Base):
    """One admin-managed source (phase 35; kind discriminator, phase 38).

    The UI-maintained list the Sync button (phase 32) and import_docs
    (phase 28) import from. ``kind`` discriminates: ``git`` rows carry a
    repo ``url`` (cloned/pulled), ``local`` rows carry an existing
    directory ``path`` (walked directly). DB rows win over the
    BOR_GIT_SOURCES env var (git-only fallback), which is a fallback
    while this table is empty (see
    app.rag.git_sources.effective_git_sources).
    """

    __tablename__ = "git_sources"

    id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
    url: Mapped[str] = mapped_column(Text, unique=True, nullable=False)
    #: Source-kind discriminator (phase 38): "git" (default) or "local"
    #: — enforced by the ``ck_git_sources_kind`` CHECK constraint.
    kind: Mapped[str] = mapped_column(Text, default="git", server_default="'git'")
    #: Absolute directory of a ``local`` source; NULL for git rows.
    #: Unique — Postgres treats NULLs as distinct under a unique index.
    path: Mapped[str | None] = mapped_column(Text, unique=True)
    added_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), server_default=func.now())


class SavedChat(Base):
    """One owner-saved chat conversation (phase 50).

    Only conversations the owner explicitly **Saves** are stored —
    ``/api/chat`` itself stays stateless (A10, owner-locked extension
    2026-08-29) and nothing is stored about a conversation that was not
    saved. ``messages`` holds the exact ``bor.chat.v1`` localStorage
    record shape (phase 14 — raw text, never HTML), so a saved chat
    restores pixel-identical through the existing
    ``renderStoredMessage`` path.
    """

    __tablename__ = "saved_chats"

    id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
    #: Auto-title (the first question, API-side). Plain column on purpose:
    #: a future rename needs no migration.
    title: Mapped[str] = mapped_column(String(500))
    #: ``list[dict]`` in the ``bor.chat.v1`` record shape
    #: (``{who, text, sources?, deflected?, suggestions?, thinking?,
    #: tools?, stopped?}``); the API always supplies a list, so no
    #: default is needed.
    messages: Mapped[list] = mapped_column(JSONB)
    #: Anonymous share link (phase 51): a 128-bit ``uuid4`` token; when
    #: set, the chat is publicly readable at ``/shared/<token>`` without
    #: any admin session, and unsharing (token → NULL) revokes it.
    #: Unique — Postgres treats NULLs as distinct under a unique index
    #: (the ``git_sources.path`` precedent, phase 38), so any number of
    #: unshared chats coexist while two identical tokens can never exist.
    share_token: Mapped[uuid.UUID | None] = mapped_column(
        UUID(as_uuid=True), unique=True, nullable=True
    )
    #: The sources version (KB generation) the conversation was saved
    #: against (phase 53): stamped by the API at save time. Existing
    #: rows (saved before the counter existed) stamp ``0`` — "the
    #: pre-counter KB" — and become stale on the first KB-changing sync
    #: (stale = ``sources_version < current``, computed server-side by
    #: the chats API, phase 53 task 03).
    sources_version: Mapped[int] = mapped_column(Integer, server_default="0")
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), server_default=func.now())
    updated_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), server_default=func.now(), onupdate=func.now()
    )