import re
from html import escape
from pathlib import Path
from urllib.parse import quote

import streamlit as st
from streamlit_pdf_viewer import pdf_viewer
from utils import (
    APP_ICON_PATH,
    convert_office_to_pdf,
    download_github_file,
    get_manifest,
    get_mime_type,
    inject_theme,
    render_page_header,
    render_sidebar,
    render_stat_cards,
    summarize_manifest,
    summarize_subject_catalog,
)

st.set_page_config(
    page_title="Study Materials Hub", page_icon=APP_ICON_PATH, layout="wide"
)
inject_theme()

# No longer need strict MIME-type mappings since we check extensions robustly.


def format_file_label(filename):
    """Return a cleaner display label for a stored filename."""
    stem = Path(filename).stem
    return re.sub(r"[._-]+", " ", stem).strip() or filename


def get_file_type_label(filename, file_mime):
    """Return a short human-readable file type label."""
    suffix = Path(filename).suffix.lower().lstrip(".")
    if suffix:
        return suffix
    if file_mime.startswith("text/"):
        return "text"
    if file_mime == "application/pdf":
        return "pdf"
    return file_mime.rsplit("/", 1)[-1]


def display_pdf(file_content):
    """Display PDF using streamlit-pdf-viewer."""
    pdf_viewer(file_content, width="100%", height=700)


def display_office_document(file_content, download_url, filename):
    """Display Word / PowerPoint files by converting to PDF server-side.

    Uses pure Python libraries to extract content and render a PDF preview.
    If the conversion fails or is unsupported, it falls back to a link
    that opens the file in Microsoft Office Web Viewer in a new tab.
    """
    suffix = Path(filename).suffix.lower().lstrip(".")
    type_label = "presentation" if suffix in ("ppt", "pptx") else "document"

    with st.spinner(f"Converting {type_label} to PDF for preview…"):
        pdf_bytes = convert_office_to_pdf(file_content, filename)

    if pdf_bytes:
        pdf_viewer(pdf_bytes, width="100%", height=700)
        st.caption(
            f"Inline preview of `{format_file_label(filename)}` "
            "(converted to PDF on the server)."
        )
    else:
        # Fallback – open in Office Web Viewer in a new tab
        encoded_url = quote(download_url, safe="")
        preview_url = (
            f"https://view.officeapps.live.com/op/view.aspx?src={encoded_url}"
        )
        st.markdown(
            f"""
            <section class="plexi-callout" style="text-align:center;padding:2.5rem 1.5rem;">
                <div style="font-size:3rem;margin-bottom:0.6rem;">📄</div>
                <div class="plexi-sidecard-title">{format_file_label(filename)}</div>
                <div class="plexi-muted" style="margin-bottom:1rem;">
                    Server-side conversion is not available right now.
                    Open the {type_label} in Microsoft Office Web Viewer instead.
                </div>
            </section>
            """,
            unsafe_allow_html=True,
        )
        st.link_button(
            f"🔗  Open {type_label.capitalize()} in Office Viewer",
            preview_url,
            use_container_width=True,
            type="primary",
        )
        st.caption(
            "Powered by Microsoft Office Web Viewer. "
            "You can also download the file directly using the button on the right."
        )

try:
    manifest = get_manifest()
except Exception as err:
    st.error(f"Failed to load materials catalog: {err}")
    st.stop()

semester_names = sorted(manifest.keys()) if manifest else []
catalog_summary = summarize_manifest(manifest) if manifest else None

if not semester_names:
    st.info("No study materials are available yet. Check back later.")
    st.stop()

selected_semester = None
selected_subject = None
selected_type = None
selected_file_name = None

with st.container():
    render_page_header(
        "Material hub",
        "Browse the catalog without losing context",
        (
            "Move from semester to file in a single flow, preview supported files in "
            "place, and download the exact asset you want from the shared materials "
            "repository."
        ),
        badges=[
            f"{catalog_summary['semester_count']} semesters"
            if catalog_summary
            else None,
            f"{catalog_summary['file_count']} files" if catalog_summary else None,
            "Inline document preview",
        ],
    )

st.markdown(
    '<div class="plexi-section-label">Refine Your Selection</div>',
    unsafe_allow_html=True,
)
st.markdown(
    """
    <section class="plexi-panel">
        <div class="plexi-sidecard-title">Catalog filters</div>
        <div class="plexi-muted">
            Narrow the collection by semester, then drill into one subject and file.
        </div>
    </section>
    """,
    unsafe_allow_html=True,
)

filter_cols = st.columns(4, gap="medium")
with filter_cols[0]:
    selected_semester = st.selectbox("Semester", semester_names, key="hub_semester")

subjects = sorted(manifest[selected_semester].keys())
with filter_cols[1]:
    selected_subject = st.selectbox("Subject", subjects, key="hub_subject")

subject_data = manifest[selected_semester][selected_subject]
subject_summary = summarize_subject_catalog(subject_data)
types = subject_summary["types"]
with filter_cols[2]:
    selected_type = st.selectbox("Material Type", types, key="hub_type")

files_list = subject_data[selected_type]
file_names = [file_entry["name"] for file_entry in files_list]
with filter_cols[3]:
    selected_file_name = (
        st.selectbox(
            "File",
            file_names,
            key="hub_file",
            format_func=format_file_label,
        )
        if file_names
        else None
    )

selected_file_obj = (
    next((item for item in files_list if item["name"] == selected_file_name), None)
    if selected_file_name
    else None
)

render_stat_cards(
    [
        {
            "label": "Current Subject",
            "value": selected_subject,
            "note": f"{selected_semester} collection currently in focus.",
        },
        {
            "label": "Available Files",
            "value": subject_summary["file_count"],
            "note": "All assets available for this subject across material types.",
        },
        {
            "label": "Material Types",
            "value": subject_summary["type_count"],
            "note": ", ".join(subject_summary["types"]),
        },
        {
            "label": "Current Bucket",
            "value": len(files_list),
            "note": f"Files available inside {selected_type}.",
        },
    ]
)

render_sidebar()

if not selected_file_obj:
    st.info("No files were found for this combination yet.")
    st.stop()

try:
    file_content = download_github_file(selected_file_obj["download_url"])
    file_mime = get_mime_type(selected_file_obj["name"])
except Exception as err:
    st.error(f"Error loading file: {err}")
    st.stop()

if not file_content:
    st.error("The selected file could not be downloaded.")
    st.stop()

st.markdown(
    '<div class="plexi-section-label">Preview And Download</div>',
    unsafe_allow_html=True,
)

preview_col, info_col = st.columns([1.7, 0.95], gap="large")

with preview_col:
    st.markdown(
        f"""
        <section class="plexi-panel">
            <div class="plexi-kicker">{selected_semester}</div>
            <div class="plexi-sidecard-title">{format_file_label(selected_file_obj["name"])}</div>
            <div class="plexi-muted">
                {selected_subject} / {selected_type}
            </div>
        </section>
        """,
        unsafe_allow_html=True,
    )

    ext = Path(selected_file_obj["name"]).suffix.lower()

    if ext == ".pdf":
        display_pdf(file_content)
    elif ext in (".ppt", ".pptx", ".doc", ".docx"):
        display_office_document(
            file_content, selected_file_obj["download_url"], selected_file_obj["name"]
        )
    elif file_mime.startswith("text/"):
        # Basic text preview support (optional, if needed)
        st.code(file_content.decode("utf-8", errors="replace"))
    else:
        st.info(
            "Preview is not available for this file type. Download it to inspect the content."
        )

with info_col:
    st.markdown(
        """
        <section class="plexi-callout">
            <div class="plexi-sidecard-title">Selected file</div>
            <div class="plexi-muted">
                Download the current file or switch to another asset in the same bucket.
            </div>
        </section>
        """,
        unsafe_allow_html=True,
    )
    st.download_button(
        label="Download File",
        data=file_content,
        file_name=selected_file_obj["name"],
        mime=file_mime,
        use_container_width=True,
        type="primary",
    )

    st.markdown(
        """
        <section class="plexi-panel">
            <div class="plexi-sidecard-title">File details</div>
        </section>
        """,
        unsafe_allow_html=True,
    )
    st.markdown(
        f"""
        <section class="plexi-meta">
            <div class="plexi-meta-row">
                <div class="plexi-meta-key">Semester</div>
                <div class="plexi-meta-value">{escape(selected_semester)}</div>
            </div>
            <div class="plexi-meta-row">
                <div class="plexi-meta-key">Subject</div>
                <div class="plexi-meta-value">{escape(selected_subject)}</div>
            </div>
            <div class="plexi-meta-row">
                <div class="plexi-meta-key">Material Type</div>
                <div class="plexi-meta-value">{escape(selected_type)}</div>
            </div>
            <div class="plexi-meta-row">
                <div class="plexi-meta-key">Format</div>
                <div class="plexi-meta-value">{escape(get_file_type_label(selected_file_obj["name"], file_mime).upper())}</div>
            </div>
        </section>
        """,
        unsafe_allow_html=True,
    )

    st.markdown(
        """
        <section class="plexi-panel">
            <div class="plexi-sidecard-title">More in this bucket</div>
        </section>
        """,
        unsafe_allow_html=True,
    )
    bucket_items = []
    for file_name in file_names:
        item_class = "current" if file_name == selected_file_obj["name"] else ""
        label = "Current" if file_name == selected_file_obj["name"] else "Available"
        bucket_items.append(
            f'<li class="{item_class}">{escape(label)}: {escape(format_file_label(file_name))}</li>'
        )
    st.markdown(
        f'<section class="plexi-meta"><ul class="plexi-filelist">{"".join(bucket_items)}</ul></section>',
        unsafe_allow_html=True,
    )