from __future__ import annotations

from typing import Any

from app.schemas.knowledge import (
    KnowledgePreviewBlockRead,
    KnowledgePreviewPageRead,
    KnowledgePreviewStatRead,
)
from app.services.knowledge_constants import IMAGE_EXTENSIONS, TEXT_EXTENSIONS
from app.services.knowledge_document_extractors import (
    _extract_docx_text,
    _extract_pptx_slides,
    _extract_xlsx_sheets,
    _read_text_preview,
)
from app.services.knowledge_file_utils import extract_extension, format_size


def build_preview(
    entry: dict[str, Any],
    *,
    resolve_document_path,
) -> tuple[str, list[KnowledgePreviewPageRead]]:
    extension = extract_extension(entry["original_name"])
    file_path = resolve_document_path(entry)

    if extension == "pdf":
        return "pdf", []

    if extension in IMAGE_EXTENSIONS:
        return "image", []

    if extension in TEXT_EXTENSIONS:
        text = _read_text_preview(file_path)
        return "text", [_build_text_preview_page(entry, text)]

    if extension == "docx":
        text = _extract_docx_text(file_path)
        return "text", [_build_text_preview_page(entry, text)]

    if extension == "xlsx":
        return "table", _build_xlsx_preview_pages(entry, file_path)

    if extension == "pptx":
        return "slides", _build_pptx_preview_pages(entry, file_path)

    return (
        "unsupported",
        [
            KnowledgePreviewPageRead(
                title=entry["original_name"],
                subtitle="当前格式暂不支持在线解析预览。",
                stats=[
                    KnowledgePreviewStatRead(label="文件格式", value=extension.upper() or "FILE"),
                    KnowledgePreviewStatRead(
                        label="文件大小", value=format_size(entry["size_bytes"])
                    ),
                    KnowledgePreviewStatRead(label="建议操作", value="下载后查看"),
                ],
                blocks=[
                    KnowledgePreviewBlockRead(
                        heading="预览说明",
                        lines=[
                            "当前系统已支持该文件的上传、下载和权限控制。",
                            "如需在线预览，可后续接入专门的文档转换服务。",
                        ],
                    )
                ],
            )
        ],
    )


def _build_text_preview_page(entry: dict[str, Any], text: str) -> KnowledgePreviewPageRead:
    lines = [line.strip() for line in text.splitlines() if line.strip()]
    if not lines:
        lines = ["文件内容为空，或当前文档未提取到可展示文本。"]

    groups = [lines[index : index + 8] for index in range(0, min(len(lines), 24), 8)]
    blocks = [
        KnowledgePreviewBlockRead(heading=f"内容片段 {index + 1}", lines=group)
        for index, group in enumerate(groups)
    ]

    return KnowledgePreviewPageRead(
        title=entry["original_name"],
        subtitle="文本提取预览",
        stats=[
            KnowledgePreviewStatRead(label="文件格式", value=entry["extension"].upper() or "TEXT"),
            KnowledgePreviewStatRead(label="可见行数", value=str(len(lines))),
            KnowledgePreviewStatRead(label="文件大小", value=format_size(entry["size_bytes"])),
        ],
        blocks=blocks,
    )


def _build_xlsx_preview_pages(entry: dict[str, Any], file_path) -> list[KnowledgePreviewPageRead]:
    sheets = _extract_xlsx_sheets(file_path)
    if not sheets:
        sheets = [("Sheet 1", [["未提取到表格内容。"]])]

    preview_pages: list[KnowledgePreviewPageRead] = []
    sheet_count = len(sheets)
    for sheet_name, rows in sheets[:8]:
        visible_rows = rows[:12] if rows else [["未提取到表格内容。"]]
        blocks = [
            KnowledgePreviewBlockRead(
                heading=f"第 {index + 1} 行",
                lines=[" | ".join((cell or "") for cell in row)],
            )
            for index, row in enumerate(visible_rows)
        ]

        preview_pages.append(
            KnowledgePreviewPageRead(
                title=sheet_name,
                subtitle="表格内容预览",
                stats=[
                    KnowledgePreviewStatRead(label="工作表数量", value=str(sheet_count)),
                    KnowledgePreviewStatRead(label="预览行数", value=str(len(visible_rows))),
                    KnowledgePreviewStatRead(
                        label="文件大小", value=format_size(entry["size_bytes"])
                    ),
                ],
                blocks=blocks,
            )
        )

    return preview_pages


def _build_pptx_preview_pages(entry: dict[str, Any], file_path) -> list[KnowledgePreviewPageRead]:
    slides = _extract_pptx_slides(file_path)
    if not slides:
        slides = [["未提取到幻灯片文本。"]]

    pages: list[KnowledgePreviewPageRead] = []
    for index, slide_lines in enumerate(slides[:8]):
        pages.append(
            KnowledgePreviewPageRead(
                title=entry["original_name"],
                subtitle=f"幻灯片 {index + 1}",
                stats=[
                    KnowledgePreviewStatRead(label="页码", value=str(index + 1)),
                    KnowledgePreviewStatRead(label="文本条数", value=str(len(slide_lines))),
                    KnowledgePreviewStatRead(label="文件格式", value="PPTX"),
                ],
                blocks=[
                    KnowledgePreviewBlockRead(
                        heading="幻灯片内容",
                        lines=slide_lines or ["该页未提取到文本内容。"],
                    )
                ],
            )
        )

    return pages