"""Core Pydantic v2 document models."""

from __future__ import annotations

from enum import StrEnum
from uuid import UUID, uuid4

from pydantic import BaseModel, Field, field_validator, model_validator

# ──────────────────────────────────────────────────────────────────────────────
# Enums
# ──────────────────────────────────────────────────────────────────────────────


class Language(StrEnum):
    """ISO 639-1 language codes supported by the corpus."""

    km = "km"
    en = "en"
    mixed = "mixed"
    unknown = "unknown"


class Category(StrEnum):
    """Document category taxonomy."""

    government_report = "government_report"
    government_form = "government_form"
    law = "law"
    gazette = "gazette"
    book = "book"
    research_paper = "research_paper"
    manual = "manual"
    annual_report = "annual_report"
    financial_report = "financial_report"
    certificate = "certificate"
    contract = "contract"
    invoice = "invoice"
    receipt = "receipt"
    newspaper = "newspaper"
    magazine = "magazine"
    presentation = "presentation"
    other = "other"


class DeduplicationStrategy(StrEnum):
    sha256 = "sha256"
    simhash = "simhash"
    both = "both"


# ──────────────────────────────────────────────────────────────────────────────
# Sub-models
# ──────────────────────────────────────────────────────────────────────────────


class PageMeta(BaseModel):
    """Per-page metadata extracted from a PDF."""

    page_number: int = Field(..., ge=1, description="1-indexed page number")
    width_pt: float = Field(..., gt=0, description="Page width in points")
    height_pt: float = Field(..., gt=0, description="Page height in points")
    text_char_count: int = Field(default=0, ge=0)
    image_count: int = Field(default=0, ge=0)
    has_text_layer: bool = False


class ValidationResult(BaseModel):
    """Result of schema + content validation for a document."""

    is_valid: bool
    errors: list[str] = Field(default_factory=list)
    warnings: list[str] = Field(default_factory=list)

    @property
    def has_warnings(self) -> bool:
        return len(self.warnings) > 0


# ──────────────────────────────────────────────────────────────────────────────
# Core Model
# ──────────────────────────────────────────────────────────────────────────────


class DocumentMeta(BaseModel):
    """Complete metadata for a single corpus document."""

    model_config = {"use_enum_values": True}

    # Identity
    id: UUID = Field(default_factory=uuid4, description="Unique document UUID")
    filename: str = Field(..., min_length=1, description="PDF filename (no path)")

    # Classification
    language: Language = Language.unknown
    category: Category = Category.other

    # Dimensions
    pages: int = Field(..., ge=1, description="Total page count")
    file_size_bytes: int = Field(..., ge=0, description="Raw PDF file size in bytes")

    # Content flags
    native_pdf: bool = Field(False, description="True if text is embedded in the PDF")
    scanned: bool = Field(False, description="True if the PDF requires OCR")
    has_tables: bool = False
    has_images: bool = False
    has_header: bool = False
    has_footer: bool = False

    # Deduplication
    sha256: str | None = Field(None, description="SHA-256 hex digest of raw file bytes")
    simhash: int | None = Field(None, description="SimHash fingerprint of extracted text")

    # Provenance
    source: str | None = Field(None, description="Source URL or institution name")
    license: str | None = Field(None, description="Original document license")

    # Paths (relative to corpus root)
    pdf_path: str | None = None
    preview_path: str | None = Field(None, description="Path to the preview image folder")

    # Per-page detail (optional, not always populated)
    pages_meta: list[PageMeta] = Field(default_factory=list)

    # ── Validators ────────────────────────────────────────────────────────────

    @field_validator("filename")
    @classmethod
    def filename_must_be_pdf(cls, v: str) -> str:
        if not v.lower().endswith(".pdf"):
            raise ValueError(f"filename must end with .pdf, got: {v!r}")
        return v

    @field_validator("sha256")
    @classmethod
    def sha256_format(cls, v: str | None) -> str | None:
        if v is not None and len(v) != 64:
            raise ValueError("sha256 must be a 64-character hex string")
        return v

    @model_validator(mode="after")
    def pages_meta_length(self) -> DocumentMeta:
        if self.pages_meta and len(self.pages_meta) != self.pages:
            raise ValueError(
                f"pages_meta has {len(self.pages_meta)} entries but pages={self.pages}"
            )
        return self

    # ── Helpers ───────────────────────────────────────────────────────────────

    @property
    def file_size_kb(self) -> float:
        return self.file_size_bytes / 1024

    @property
    def file_size_mb(self) -> float:
        return self.file_size_bytes / (1024 * 1024)

    def to_flat_dict(self) -> dict[str, object]:
        """Return a flat dict suitable for a Polars row (no nested objects)."""
        return {
            "id": str(self.id),
            "filename": self.filename,
            "language": self.language,
            "category": self.category,
            "pages": self.pages,
            "file_size_bytes": self.file_size_bytes,
            "native_pdf": self.native_pdf,
            "scanned": self.scanned,
            "has_tables": self.has_tables,
            "has_images": self.has_images,
            "has_header": self.has_header,
            "has_footer": self.has_footer,
            "sha256": self.sha256,
            "simhash": self.simhash,
            "source": self.source,
            "license": self.license,
            "pdf_path": self.pdf_path,
            "preview_path": self.preview_path,
        }