"""
Email sender module for ScrAIbe.

Sends transcription outputs (TXT, JSON, etc.) via SMTP.
All credentials are configured via environment variables.
Supports both plain text and HTML email bodies.
Template placeholders are primarily filled via environment variables.
"""

import base64
import json
import logging
import os
import re
import smtplib
from email import encoders
from email.mime.base import MIMEBase
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from typing import Any, Dict, List, Optional

from docx import Document
from docx.oxml import OxmlElement
from docx.oxml.ns import qn
from docx.shared import Inches, Pt
from docx.enum.text import WD_ALIGN_PARAGRAPH

logger = logging.getLogger("scraibe.email_sender")


class EmailError(Exception):
    pass


def get_email_config():
    """
    Read email configuration from environment variables.
    Raises EmailError if required fields are missing.
    """
    smtp_host = os.getenv("EMAIL_SMTP_HOST")
    smtp_port = os.getenv("EMAIL_SMTP_PORT")
    smtp_user = os.getenv("EMAIL_SMTP_USER")
    smtp_password = os.getenv("EMAIL_SMTP_PASSWORD")
    from_address = os.getenv("EMAIL_FROM_ADDRESS")
    use_tls_str = os.getenv("EMAIL_SMTP_USE_TLS", "true").strip().lower()
    use_tls = use_tls_str not in ("false", "0", "no")

    if not all([smtp_host, smtp_port, smtp_user, smtp_password, from_address]):
        raise EmailError(
            "Email configuration incomplete. "
            "Ensure EMAIL_SMTP_HOST, EMAIL_SMTP_PORT, EMAIL_SMTP_USER, "
            "EMAIL_SMTP_PASSWORD, and EMAIL_FROM_ADDRESS are set."
        )

    return {
        "smtp_host": smtp_host,
        "smtp_port": int(smtp_port),
        "smtp_user": smtp_user,
        "smtp_password": smtp_password,
        "from_address": from_address,
        "use_tls": use_tls,
    }


def _load_css(path: str) -> str:
    """
    Load CSS file content if it exists.
    """
    if not path or not os.path.exists(path):
        return ""
    with open(path, "r", encoding="utf-8") as f:
        return f.read()


def _email_logo_html() -> str:
    """
    Return a subtle watermark-style logo for emails.

    - Priority:
      1) EMAIL_LOGO_URL (direct URL)
      2) EMAIL_LOGO_PATH (local file as base64)
    - Style: small, faint, bottom-right, non-intrusive.
    """
    logo_url = os.getenv("EMAIL_LOGO_URL")
    src = logo_url

    if not logo_url:
        logo_path = os.getenv("EMAIL_LOGO_PATH", "/app/src/misc/logo1.png")
        if os.path.exists(logo_path):
            try:
                with open(logo_path, "rb") as f:
                    b64 = base64.b64encode(f.read()).decode("utf-8")
                src = f"data:image/png;base64,{b64}"
            except Exception:
                src = None

    if not src:
        return ""

    # Watermark: bottom-right, low opacity, compact
    return (
        f'<div style="text-align: right; margin-top: 24px; opacity: 0.15;">'
        f'<img src="{src}" alt="Logo" style="max-width: 90px; height: auto; display: inline-block;" />'
        f'</div>'
    )


def _accent_color() -> str:
    """
    Accent color for UI and emails.
    Default: #7C6DA0
    """
    return os.getenv("EMAIL_ACCENT_COLOR", "#7C6DA0")


def build_template_context(**runtime_kwargs: Any) -> Dict[str, Any]:
    """
    Build a context dict for templates from:
      - environment variables (base, customizable)
      - runtime-provided values (override env if present)

    Environment variables:
      - EMAIL_CONTACT_ADDRESS: value for {contact_email}
      - EMAIL_CSS_PATH: path to mail_style.css (optional; we inline it)
      - EMAIL_LOGO_URL: URL for email logo (preferred)
      - EMAIL_LOGO_PATH: fallback local path for email logo
      - EMAIL_ACCENT_COLOR: accent color (default #7C6DA0)
    """
    # Load and inline mail_style.css for consistent email styling
    css_path = os.getenv("EMAIL_CSS_PATH", "/app/src/misc/mail_style.css")
    css_text = _load_css(css_path)

    # Build logo HTML (URL or local fallback)
    logo_html = _email_logo_html()

    # Accent color
    accent = _accent_color()

    ctx: Dict[str, Any] = {
        "contact_email": os.getenv("EMAIL_CONTACT_ADDRESS", "support@example.com"),
        "email_css": css_text,
        "email_logo": logo_html,
        "accent_color": accent,
    }

    # Runtime values override env if provided
    if runtime_kwargs:
        ctx.update(runtime_kwargs)

    return ctx


def load_template(template_name: str, **runtime_kwargs: Any) -> str:
    """
    Load an HTML email template from misc/ and render placeholders.

    Expects files like:
        /app/src/misc/upload_notification_template.html
        /app/src/misc/success_template.html
        /app/src/misc/error_notification_template.html
    """
    base = os.getenv("SCRAIBE_TEMPLATES_DIR", "/app/src/misc")
    path = os.path.join(base, template_name)

    if not os.path.exists(path):
        raise EmailError(f"Email template not found: {path}")

    with open(path, "r", encoding="utf-8") as f:
        template = f.read()

    # Build context from env + runtime
    ctx = build_template_context(**runtime_kwargs)

    # Replace {placeholder} style variables safely
    try:
        return template.format(**ctx)
    except KeyError as e:
        raise EmailError(f"Missing template variable: {e}")


def send_email(
    to: str,
    subject: str,
    body: str,
    html: Optional[str],
    attachments: List[str],
    cc: Optional[str] = None,
) -> bool:
    """
    Send an email with optional HTML body and file attachments.

    Args:
        to: Comma-separated list of recipient email addresses.
        subject: Email subject.
        body: Email body (plain text).
        html: Email body (HTML), or None.
        attachments: List of file paths to attach.
        cc: Comma-separated list of CC email addresses (optional).

    Returns:
        True if sent successfully.

    Raises:
        EmailError if sending fails.
    """
    try:
        cfg = get_email_config()
    except EmailError as e:
        logger.error("Email configuration error: %s", e)
        raise

    # Parse recipients
    to_list = [addr.strip() for addr in to.split(",") if addr.strip()]
    cc_list = [addr.strip() for addr in cc.split(",") if addr.strip()] if cc else []

    if not to_list:
        raise EmailError("No valid 'To' email addresses provided.")

    # Ensure subject is never blank
    if not subject or not subject.strip():
        logger.warning("Subject was blank or missing; using default subject.")
        subject = "ScrAIbe: Your transcript is ready"

    subject = subject.strip()

    has_attachments = bool(attachments)

    # Build the text/HTML part (alternative)
    alt = MIMEMultipart("alternative")
    alt.attach(MIMEText(body, "plain"))
    if html:
        alt.attach(MIMEText(html, "html"))

    if has_attachments:
        # Outer message: multipart/mixed with headers
        msg = MIMEMultipart("mixed")
        msg["From"] = cfg["from_address"]
        msg["To"] = ", ".join(to_list)
        if cc_list:
            msg["Cc"] = ", ".join(cc_list)
        msg["Subject"] = subject

        # Attach the alternative (text/HTML) part
        msg.attach(alt)

        # Attach files
        for file_path in attachments:
            if not os.path.isfile(file_path):
                logger.warning("Attachment file not found, skipping: %s", file_path)
                continue

            try:
                with open(file_path, "rb") as f:
                    part = MIMEBase("application", "octet-stream")
                    part.set_payload(f.read())
                    encoders.encode_base64(part)
                    part.add_header(
                        "Content-Disposition",
                        "attachment",
                        filename=os.path.basename(file_path),
                    )
                    msg.attach(part)
            except Exception as e:
                logger.warning("Failed to attach file %s: %s", file_path, e)
    else:
        # No attachments: use the alternative part as the root message
        msg = alt
        msg["From"] = cfg["from_address"]
        msg["To"] = ", ".join(to_list)
        if cc_list:
            msg["Cc"] = ", ".join(cc_list)
        msg["Subject"] = subject

    # Connect and send
    try:
        if cfg["use_tls"]:
            server = smtplib.SMTP(cfg["smtp_host"], cfg["smtp_port"], timeout=30)
            server.ehlo()
            server.starttls()
            server.ehlo()
        else:
            server = smtplib.SMTP(cfg["smtp_host"], cfg["smtp_port"], timeout=30)
            server.ehlo()

        server.login(cfg["smtp_user"], cfg["smtp_password"])
        server.sendmail(
            cfg["from_address"],
            to_list + cc_list,
            msg.as_string(),
        )
        server.quit()
        logger.info(
            "Email sent to %s (CC: %s) with subject: %s",
            to_list,
            cc_list or "None",
            subject,
        )
        return True

    except Exception as e:
        logger.error("Failed to send email: %s", e)
        raise EmailError(f"Failed to send email: {e}")


# ------------ DOCX helpers ------------

# Namespaces
W_NS = "http://schemas.openxmlformats.org/wordprocessingml/2006/main"


def _set_element_attr(elem, attr, value):
    elem.set(f"{{{W_NS}}}{attr}", str(value))


def _create_transcript_section_properties(section):
    """
    Configure the section properties for transcript DOCX:
    - Margins: 1 inch all sides
    - Single column layout
    - No built-in line numbering (we embed line numbers as text for portability)
    - Remove document grid to avoid off-by-one line numbering
    """
    sectPr = section._sectPr

    # Margins: 1 inch = 1440 twips
    pgMar = sectPr.find(f"{{{W_NS}}}pgMar")
    if pgMar is None:
        pgMar = OxmlElement("w:pgMar")
        sectPr.append(pgMar)
    _set_element_attr(pgMar, "top", "1440")
    _set_element_attr(pgMar, "right", "1440")
    _set_element_attr(pgMar, "bottom", "1440")
    _set_element_attr(pgMar, "left", "1440")
    _set_element_attr(pgMar, "header", "720")
    _set_element_attr(pgMar, "footer", "720")
    _set_element_attr(pgMar, "gutter", "0")

    # Ensure single column (no multi-column layout)
    cols = sectPr.find(f"{{{W_NS}}}cols")
    if cols is not None:
        _set_element_attr(cols, "num", "1")
        _set_element_attr(cols, "space", "720")

    # Remove document grid entirely
    for docGrid in sectPr.findall(f"{{{W_NS}}}docGrid"):
        sectPr.remove(docGrid)

    # Remove any built-in line numbering; we will use text-based line numbers
    for lnNumType in sectPr.findall(f"{{{W_NS}}}lnNumType"):
        sectPr.remove(lnNumType)


def _add_transcript_paragraph(doc, line_text, line_number):
    """
    Add a single transcript line as a paragraph with an embedded line number.
    Uses a left tab stop so the line number appears in the left margin area,
    independent of built-in line numbering, ensuring consistent behavior
    across Word, LibreOffice, Google Docs, etc.
    """
    line_text = line_text.strip()
    if not line_text:
        return

    p = doc.add_paragraph()

    # Set up paragraph formatting:
    # - No left indent; we control spacing via tab stop
    # - Single line spacing, no extra before/after
    pPr = p._p.get_or_add_pPr()

    # Remove any default indent
    pPr.find(f"{{{W_NS}}}ind") and pPr.remove(pPr.find(f"{{{W_NS}}}ind"))

    # Define a left tab stop for line numbers (e.g. 360 twips ≈ 0.25")
    tabs = OxmlElement("w:tabs")
    tab = OxmlElement("w:tab")
    tab.set("{http://schemas.openxmlformats.org/wordprocessingml/2006/main}val", "left")
    tab.set("{http://schemas.openxmlformats.org/wordprocessingml/2006/main}pos", "360")
    tabs.append(tab)
    pPr.append(tabs)

    spacing = OxmlElement("w:spacing")
    _set_element_attr(spacing, "before", "0")
    _set_element_attr(spacing, "after", "0")
    _set_element_attr(spacing, "line", "240")       # 12pt in twips
    _set_element_attr(spacing, "lineRule", "auto")
    pPr.append(spacing)

    # Try to match: [00:00] SPEAKER 1: content
    m = re.match(r"\[(\d+:\d+(?::\d+)?)\]\s*(.+?):\s*(.*)", line_text)

    # Line number run (no underline)
    run_ln = p.add_run(str(line_number))
    run_ln.font.name = "Courier"
    run_ln.font.size = Pt(12)
    run_ln.underline = False

    # Tab between line number and content
    run_tab = p.add_run("\t")
    run_tab.font.name = "Courier"
    run_tab.font.size = Pt(12)
    run_tab.underline = False

    if m:
        ts, speaker, content = m.groups()
        label_text = f"[{ts}] {speaker.upper()}:"

        # Label run (underline)
        run_label = p.add_run(label_text)
        run_label.underline = True
        run_label.font.name = "Courier"
        run_label.font.size = Pt(12)

        # Space run (no underline)
        run_space = p.add_run(" ")
        run_space.underline = False
        run_space.font.name = "Courier"
        run_space.font.size = Pt(12)

        # Content run (no underline)
        run_txt = p.add_run(content.strip())
        run_txt.underline = False
        run_txt.font.name = "Courier"
        run_txt.font.size = Pt(12)
    else:
        # Non-standard line: plain text
        run = p.add_run(line_text)
        run.underline = False
        run.font.name = "Courier"
        run.font.size = Pt(12)


# ------------ Public DOCX functions ------------

def create_transcript_docx(text: str, filename: str):
    """
    Create a transcript DOCX with:
    - 1" margins on all sides
    - 12pt Courier font
    - Embedded line numbers starting at 1 on the first page
      (portable across Word, LibreOffice, Google Docs)
    - Proper formatting for timestamps and speaker labels
    """
    doc = Document()

    # Set base font (Normal style)
    style = doc.styles["Normal"]
    style.font.name = "Courier"
    style.font.size = Pt(12)

    # Remove any default paragraphs (ensure no phantom first line)
    body = doc.element.body
    for p in list(body.findall(f"{{{W_NS}}}p")):
        body.remove(p)

    # Configure section properties (margins, no built-in line numbering)
    _create_transcript_section_properties(doc.sections[0])

    # Add transcript lines with embedded line numbers
    lines = text.strip().splitlines()
    for idx, line in enumerate(lines, start=1):
        _add_transcript_paragraph(doc, line, line_number=idx)

    # Save
    doc.save(filename)


def create_summary_docx(text: str, filename: str):
    """
    Create a summary DOCX with:
    - 1" margins on all sides
    - 12pt Courier font
    - No line numbering
    """
    doc = Document()

    # Base font
    style = doc.styles["Normal"]
    style.font.name = "Courier"
    style.font.size = Pt(12)

    # Margins: 1 inch all sides
    for section in doc.sections:
        section.left_margin = Inches(1.0)
        section.right_margin = Inches(1.0)
        section.top_margin = Inches(1.0)
        section.bottom_margin = Inches(1.0)

    # Remove default paragraph
    body = doc.element.body
    for p in list(body.findall(f"{{{W_NS}}}p")):
        body.remove(p)

    # Add summary content
    lines = text.strip().splitlines()
    for line in lines:
        line = line.strip()
        if not line:
            continue
        p = doc.add_paragraph(line)
        p.paragraph_format.space_after = Pt(4)

    doc.save(filename)