"""Scoped file-read and search tools for the project folder feature."""
from __future__ import annotations

from langchain_core.tools import tool

from app.core.folder_indexer import _extract_docx_text, _extract_pdf_text
from app.core.ws_context import execute_on_client

# Cap returned slice size to keep tool output under control.
_MAX_RETURN_CHARS = 50_000
_MAX_SEARCH_MATCHES = 20


def _is_unsafe_path(rel: str) -> bool:
    if not rel:
        return True
    norm = rel.replace("\\", "/")
    if norm.startswith("/"):
        return True
    # Windows drive letter
    if len(rel) >= 2 and rel[1] == ":":
        return True
    parts = norm.split("/")
    return ".." in parts


async def _fetch_file(project_id: str, relative_path: str, offset: int, length: int) -> dict:
    """Return the raw Electron tool_result dict for a file read."""
    return await execute_on_client(
        action="read_project_folder_file",
        data={
            "projectId": project_id,
            "relativePath": relative_path,
            "offset": offset,
            "length": length,
        },
    )


def _decode(result: dict) -> tuple[str, str, int]:
    """Decode a tool_result into (text, kind, total_size). For pdf/docx,
    extracts text from base64. For images, returns a placeholder string.
    For text, content is already a sliced utf-8 string.
    """
    kind = result.get("kind", "text")
    content = result.get("content", "") or ""
    total = int(result.get("totalSize", 0) or 0)
    if kind == "image":
        return ("[Image file — cannot be navigated as text. See manifest summary.]", kind, total)
    if kind == "pdf":
        return (_extract_pdf_text(content), kind, total)
    if kind == "docx":
        return (_extract_docx_text(content), kind, total)
    return (content, kind, total)


@tool
async def read_project_folder_file(
    project_id: str,
    relative_path: str,
    offset: int = 0,
    length: int = _MAX_RETURN_CHARS,
) -> str:
    """Read a slice of a file inside the project's linked folder.

    Args:
        project_id: project ID.
        relative_path: path relative to the linked folder root.
        offset: char offset to start reading from (0 = beginning).
        length: max chars to return. Default 50000. Use smaller values to save tokens.

    Returns text content slice with a header showing position. Header tells you
    when more content is available; call again with the suggested next offset.

    For PDF / DOCX files the backend extracts text first, then applies offset/length
    on the extracted text. For images returns a placeholder; navigate with the
    manifest summary instead.
    """
    if _is_unsafe_path(relative_path):
        return "Access denied"

    result = await _fetch_file(project_id, relative_path, offset, length)
    text, kind, total_size = _decode(result)

    if not text and kind in ("missing", "error"):
        return f"File not found or unreadable: {relative_path}"

    if kind in ("pdf", "docx"):
        # Backend extracted full text — apply offset/length on chars.
        sliced = text[offset:offset + length]
        slice_end = min(offset + length, len(text))
        header = (
            f"[file={relative_path} kind={kind} offset={offset} end={slice_end} "
            f"totalChars={len(text)}]"
        )
        if slice_end < len(text):
            header += f"\n[More content available — call again with offset={slice_end}.]"
        return header + "\n" + sliced

    if kind == "text":
        slice_end = offset + len(text)
        header = (
            f"[file={relative_path} kind=text offset={offset} end={slice_end} "
            f"totalBytes={total_size}]"
        )
        if slice_end < total_size:
            header += f"\n[More content available — call again with offset={slice_end}.]"
        return header + "\n" + text

    # image or unknown
    return text


@tool
async def search_project_folder_file(
    project_id: str,
    relative_path: str,
    query: str,
    context_lines: int = 3,
) -> str:
    """Search a project folder file for a query string (case-insensitive substring).

    Args:
        project_id: project ID.
        relative_path: path relative to the linked folder root.
        query: text to search for.
        context_lines: number of lines of context around each match (default 3).

    Returns matching line ranges with surrounding context and 1-based line numbers.
    Capped at 20 matches; if more exist the header shows the total.

    Works on text, code, markdown, PDF (extracted), and DOCX (extracted).
    Images and binary files are not searchable.
    """
    if _is_unsafe_path(relative_path):
        return "Access denied"
    if not query:
        return "Empty query."

    # For text we still need full file; pass length=very large.
    result = await _fetch_file(project_id, relative_path, offset=0, length=10_000_000)
    text, kind, _ = _decode(result)

    if not text and kind in ("missing", "error"):
        return f"File not found or unreadable: {relative_path}"
    if kind == "image":
        return "Cannot search inside images."

    lines = text.splitlines()
    q = query.lower()
    matches = [i for i, line in enumerate(lines) if q in line.lower()]
    if not matches:
        return f"No matches for '{query}' in {relative_path}."

    shown = matches[:_MAX_SEARCH_MATCHES]
    snippets: list[str] = []
    for i in shown:
        start = max(0, i - context_lines)
        end = min(len(lines), i + context_lines + 1)
        block = "\n".join(f"{n + 1:5d}: {lines[n]}" for n in range(start, end))
        snippets.append(block)

    header = f"[file={relative_path} matches={len(matches)} showing={len(shown)} query='{query}']"
    body = "\n---\n".join(snippets)
    return header + "\n" + body


FOLDER_TOOLS = [read_project_folder_file, search_project_folder_file]