"""
Frox AI — File Analysis Tool

Extracts text (and light structure) from common document formats.
Each format's parser is optional-imported so the tool degrades to a
clear error for a specific format rather than failing to import at
all if one optional dependency is missing.
"""
from __future__ import annotations

from pathlib import Path
from typing import Optional

from tools.registry import tool, ToolContext


MAX_CONTENT_CHARS = 20000   # keep tool results from blowing the model's context budget


class UnsupportedFileType(ValueError):
    pass


def _parse_txt(path: Path) -> str:
    return path.read_text(encoding="utf-8", errors="replace")


def _parse_pdf(path: Path) -> str:
    try:
        import pdfplumber
    except ImportError:
        raise RuntimeError("pdfplumber is required for PDF parsing — pip install pdfplumber")

    pages = []
    with pdfplumber.open(str(path)) as pdf:
        for i, page in enumerate(pdf.pages):
            text = page.extract_text() or ""
            if text.strip():
                pages.append(f"[Page {i + 1}]\n{text}")
    return "\n\n".join(pages)


def _parse_docx(path: Path) -> str:
    try:
        import docx
    except ImportError:
        raise RuntimeError("python-docx is required for DOCX parsing — pip install python-docx")

    doc = docx.Document(str(path))
    parts = [p.text for p in doc.paragraphs if p.text.strip()]
    for table in doc.tables:
        for row in table.rows:
            parts.append(" | ".join(cell.text for cell in row.cells))
    return "\n".join(parts)


def _parse_csv(path: Path, max_rows: int = 200) -> str:
    import csv
    with open(path, newline="", encoding="utf-8", errors="replace") as f:
        reader = csv.reader(f)
        rows = list(reader)

    header = rows[0] if rows else []
    body = rows[1:max_rows + 1]
    lines = [", ".join(header)]
    lines += [", ".join(row) for row in body]
    truncated_note = f"\n[... {len(rows) - 1 - len(body)} more rows not shown]" if len(rows) - 1 > len(body) else ""
    return "\n".join(lines) + truncated_note


def _parse_xlsx(path: Path, max_rows: int = 200) -> str:
    try:
        import openpyxl
    except ImportError:
        raise RuntimeError("openpyxl is required for XLSX parsing — pip install openpyxl")

    wb = openpyxl.load_workbook(str(path), data_only=True, read_only=True)
    sheets_out = []
    for sheet in wb.worksheets:
        lines = [f"[Sheet: {sheet.title}]"]
        for i, row in enumerate(sheet.iter_rows(values_only=True)):
            if i >= max_rows:
                lines.append(f"[... more rows not shown]")
                break
            lines.append(", ".join(str(c) if c is not None else "" for c in row))
        sheets_out.append("\n".join(lines))
    return "\n\n".join(sheets_out)


def _parse_pptx(path: Path) -> str:
    try:
        from pptx import Presentation
    except ImportError:
        raise RuntimeError("python-pptx is required for PPTX parsing — pip install python-pptx")

    prs = Presentation(str(path))
    slides_out = []
    for i, slide in enumerate(prs.slides):
        lines = [f"[Slide {i + 1}]"]
        for shape in slide.shapes:
            if shape.has_text_frame and shape.text_frame.text.strip():
                lines.append(shape.text_frame.text)
            if shape.has_notes_frame if hasattr(shape, "has_notes_frame") else False:
                lines.append(f"(notes: {shape.notes_frame.text})")
        slides_out.append("\n".join(lines))
    return "\n\n".join(slides_out)


def _parse_md(path: Path) -> str:
    return path.read_text(encoding="utf-8", errors="replace")


_PARSERS = {
    ".txt": _parse_txt, ".md": _parse_md,
    ".pdf": _parse_pdf, ".docx": _parse_docx,
    ".csv": _parse_csv, ".xlsx": _parse_xlsx, ".xls": _parse_xlsx,
    ".pptx": _parse_pptx,
}


def parse_file(path: str) -> dict:
    """Parse a file into extracted text, dispatching by extension."""
    p = Path(path)
    if not p.exists():
        raise FileNotFoundError(f"File not found: {path}")

    ext = p.suffix.lower()
    parser = _PARSERS.get(ext)
    if parser is None:
        raise UnsupportedFileType(
            f"Unsupported file type: {ext!r}. Supported: {', '.join(_PARSERS)}"
        )

    text = parser(p)
    truncated = len(text) > MAX_CONTENT_CHARS
    return {
        "filename": p.name,
        "extension": ext,
        "text": text[:MAX_CONTENT_CHARS],
        "truncated": truncated,
        "char_count": len(text),
    }


@tool(
    name="file_analysis",
    description="Extract text from a document file (PDF, DOCX, TXT, MD, CSV, XLSX, PPTX)",
    timeout=30.0,
)
def file_analysis(ctx: ToolContext, file_path: str) -> dict:
    """
    Args:
        file_path: Path to the uploaded file on disk.

    Plain `def`, not `async def`: file I/O and the parsing libraries
    here (pdfplumber, python-docx, openpyxl) are all blocking, so this
    is thread-offloaded by the registry.
    """
    return parse_file(file_path)