#!/usr/bin/env python3
"""Build and send backup outcome email notifications via ns8-sendmail.

This module is the final stage of the pipeline. It takes the correlation
result and the optional repository health check result, renders both a
plain-text and an HTML email body, and dispatches the message through the
NS8 mail relay using ``runagent ns8-sendmail``.

Why ns8-sendmail / runagent?
----------------------------
NS8 modules are containerised; the cluster mail relay is exposed through
the ``runagent`` helper which bridges the host and the container network.
``ns8-sendmail`` reads the relay configuration from the NS8 cluster state,
so no SMTP settings need to be stored in this project's config file.

Correct invocation (verified against NS8 source):
    runagent ns8-sendmail -s <subject> [-f <from>] <to> [<to> ...]
    Body is read from stdin as plain text.
    ns8-sendmail does NOT parse To:/From:/Subject: headers from the body.

Outcome labels and colours used in the HTML email
--------------------------------------------------
    SUCCESS      – label "OK",       header background #2e7d32 (green)
    PARTIAL      – label "WARNING",  header background #e65100 (orange)
    REPO_FAILURE – label "CRITICAL", header background #b71c1c (red)
"""

import logging
import subprocess
from datetime import datetime, timezone
from typing import Optional

log = logging.getLogger(__name__)

# ---------------------------------------------------------------------------
# Outcome presentation maps
# ---------------------------------------------------------------------------
# Maps the three internal outcome codes to a short label and a background
# colour used in the HTML email header banner.

OUTCOME_LABEL = {
    "SUCCESS":      "OK",
    "PARTIAL":      "WARNING",
    "REPO_FAILURE": "CRITICAL",
}

OUTCOME_COLOR = {
    "SUCCESS":      "#2e7d32",  # Material green 800
    "PARTIAL":      "#e65100",  # Material deep-orange 900
    "REPO_FAILURE": "#b71c1c",  # Material red 900
}


# ---------------------------------------------------------------------------
# Command builder
# ---------------------------------------------------------------------------

def _send_cmd(subject: str, mail_from: str, mail_to: list) -> list:
    """Build the argv list for invoking ns8-sendmail via runagent.

    ``runagent`` must be in PATH, which is guaranteed for root on NS8 nodes.

    Args:
        subject:   Email subject line (already includes prefix and date).
        mail_from: Envelope From address (may be empty; ns8-sendmail has a default).
        mail_to:   List of recipient addresses.

    Returns:
        List of strings ready to pass to subprocess.run().
    """
    cmd = ["runagent", "ns8-sendmail", "-s", subject]
    if mail_from:
        cmd += ["-f", mail_from]
    cmd += mail_to
    return cmd


# ---------------------------------------------------------------------------
# Plain-text body renderer
# ---------------------------------------------------------------------------

def _build_text(correlation: dict, repo_status: Optional[dict]) -> str:
    """Render a plain-text email body from the correlation and repo results.

    Produces a human-readable report suitable for terminal mail clients and
    as a fallback for email clients that do not render HTML.

    Args:
        correlation: Dict returned by correlator.correlate_backup_status().
        repo_status: Dict returned by repo_check.check_repositories(), or None.

    Returns:
        Multi-line string (Unix line endings).
    """
    outcome = correlation["outcome"]
    lines = [
        f"NS8 Backup Monitor - {OUTCOME_LABEL[outcome]}: {outcome}",
        f"Time: {datetime.now(timezone.utc).isoformat()}",
        f"Plans: {', '.join(correlation.get('backup_ids', []))}",
        f"Modules: {correlation['succeeded']} OK / "
        f"{correlation['failed']} FAILED / {correlation['total']} total",
        "",
    ]

    # List each failed module with its error message.
    if correlation["failed_modules"]:
        lines.append("Failed modules:")
        for m in correlation["failed_modules"]:
            lines.append(f"  - [{m['module_id']}] {m['backup_id']}: {m.get('error', '?')}")
        lines.append("")

    # Append repository health check details when available.
    if repo_status:
        lines.append("Repository check:")
        for dest in repo_status.get("destinations", []):
            lines.append(
                f"  - [{dest['repo_id']}] {dest['status']}: {dest.get('error', '')}"
            )
        if repo_status.get("note"):
            lines.append(f"  NOTE: {repo_status['note']}")
        lines.append("")

    if correlation.get("note"):
        lines.append(f"Note: {correlation['note']}")

    return "\n".join(lines)


# ---------------------------------------------------------------------------
# HTML body renderer
# ---------------------------------------------------------------------------

def _build_html(correlation: dict, repo_status: Optional[dict]) -> str:
    """Render an HTML email body from the correlation and repo results.

    Produces a self-contained HTML document with:
    - A coloured header banner showing the outcome and timestamp.
    - A summary line with module counts.
    - A per-module status table with colour-coded rows (green/red).
    - An optional repository check table appended when repo_status is present.

    Inline styles are used throughout to maximise compatibility with
    webmail clients that strip <style> blocks.

    Args:
        correlation: Dict returned by correlator.correlate_backup_status().
        repo_status: Dict returned by repo_check.check_repositories(), or None.

    Returns:
        HTML string.
    """
    outcome  = correlation["outcome"]
    color    = OUTCOME_COLOR[outcome]
    label    = OUTCOME_LABEL[outcome]
    ts       = datetime.now(timezone.utc).strftime("%Y-%m-%d %H:%M UTC")
    plan_ids = ", ".join(correlation.get("backup_ids", [])) or "N/A"

    # ---------------------------------------------------------------------------
    # Per-module status table rows
    # ---------------------------------------------------------------------------
    rows = ""
    for m in correlation.get("modules", []):
        bg   = "#e8f5e9" if m["result"] == "success" else "#ffebee"
        icon = "&#10003;" if m["result"] == "success" else "&#10007;"  # ✓ / ✗
        rows += (
            f'<tr style="background:{bg}">'
            f'<td style="padding:4px 8px">{icon}</td>'
            f'<td style="padding:4px 8px">{m["module_id"]}</td>'
            f'<td style="padding:4px 8px">{m["backup_id"]}</td>'
            f'<td style="padding:4px 8px">{m.get("timestamp", "")}</td>'
            f'<td style="padding:4px 8px">{m.get("error", "") or ""}</td>'
            "</tr>"
        )

    # ---------------------------------------------------------------------------
    # Repository health check section (optional)
    # ---------------------------------------------------------------------------
    repo_section = ""
    if repo_status:
        rr = ""
        for dest in repo_status.get("destinations", []):
            bg = "#e8f5e9" if dest["status"] == "OK" else "#ffebee"
            rr += (
                f'<tr style="background:{bg}">'
                f'<td style="padding:4px 8px">{dest["repo_id"]}</td>'
                f'<td style="padding:4px 8px"><b>{dest["status"]}</b></td>'
                f'<td style="padding:4px 8px">{dest.get("error", "")}</td>'
                "</tr>"
            )
        if rr:
            repo_section = (
                "<h3 style='margin-top:24px'>Repository check</h3>"
                "<table border='1' cellspacing='0' "
                "style='border-collapse:collapse;font-size:13px;width:100%'>"
                "<thead><tr style='background:#f5f5f5'>"
                "<th style='padding:4px 8px'>Repo</th>"
                "<th style='padding:4px 8px'>Status</th>"
                f"<th style='padding:4px 8px'>Detail</th></tr></thead>"
                f"<tbody>{rr}</tbody></table>"
            )
        if repo_status.get("note"):
            repo_section += (
                f"<p style='color:#777;font-size:12px'>{repo_status['note']}</p>"
            )

    # ---------------------------------------------------------------------------
    # Assemble the full HTML document
    # ---------------------------------------------------------------------------
    return (
        "<html><body style='font-family:monospace;font-size:14px;"
        "max-width:800px;margin:auto'>"
        # Header banner
        f"<div style='background:{color};color:#fff;padding:16px 20px;"
        f"border-radius:6px 6px 0 0'>"
        f"<b>NS8 Backup Monitor &mdash; {label}: {outcome}</b><br>"
        f"<small>{ts} &bull; Plans: {plan_ids}</small></div>"
        # Body
        "<div style='border:1px solid #ddd;border-top:none;padding:16px 20px;"
        "border-radius:0 0 6px 6px'>"
        f"<p><b>{correlation['succeeded']}</b> OK &nbsp;|&nbsp;"
        f"<b>{correlation['failed']}</b> FAILED &nbsp;|&nbsp;"
        f"<b>{correlation['total']}</b> total</p>"
        # Per-module table
        "<table border='1' cellspacing='0' style='border-collapse:collapse;"
        "font-size:13px;width:100%'>"
        "<thead><tr style='background:#f5f5f5'>"
        "<th style='padding:4px 8px'></th>"
        "<th style='padding:4px 8px'>Module</th>"
        "<th style='padding:4px 8px'>Backup ID</th>"
        "<th style='padding:4px 8px'>Timestamp</th>"
        "<th style='padding:4px 8px'>Error</th>"
        f"</tr></thead><tbody>{rows}</tbody></table>"
        f"{repo_section}</div></body></html>"
    )


# ---------------------------------------------------------------------------
# Main entry point
# ---------------------------------------------------------------------------

def send_notification(
    config: dict,
    alerts: list,
    correlation: dict,
    repo_status: Optional[dict] = None,
):
    """Build and send the backup outcome email via ns8-sendmail.

    Sends the plain-text body to ns8-sendmail on stdin. The HTML body is
    currently built but not used because ns8-sendmail does not support
    multipart/alternative; it is kept for future use with a direct SMTP path.

    Args:
        config:      Parsed configuration dictionary.
        alerts:      Raw alert list from Alertmanager (used for context only).
        correlation: Dict returned by correlator.correlate_backup_status().
        repo_status: Dict returned by repo_check.check_repositories(), or None.
    """
    outcome = correlation["outcome"]
    mail_cfg = config.get("mail", {})

    # ---------------------------------------------------------------------------
    # Build subject line
    # ---------------------------------------------------------------------------
    subject_prefix = mail_cfg.get("subject_prefix", "[NS8 Backup]")
    subject = (
        f"{subject_prefix} {OUTCOME_LABEL[outcome]}: {outcome} - "
        f"{datetime.now(timezone.utc).strftime('%Y-%m-%d')}"
    )

    # ---------------------------------------------------------------------------
    # Validate recipients
    # ---------------------------------------------------------------------------
    mail_to = mail_cfg.get("to", [])
    if not mail_to:
        log.error("No mail.to recipients configured — notification not sent")
        return
    mail_from = mail_cfg.get("from", "")

    # ---------------------------------------------------------------------------
    # Render body and dispatch
    # ---------------------------------------------------------------------------
    # ns8-sendmail accepts plain text on stdin.
    body = _build_text(correlation, repo_status)
    cmd  = _send_cmd(subject, mail_from, mail_to)

    log.debug("send cmd: %s", cmd)
    try:
        proc = subprocess.run(
            cmd,
            input=body,
            text=True,
            capture_output=True,
            timeout=30,
        )
        if proc.returncode != 0:
            # Log the first non-empty output stream as the error detail.
            err = proc.stderr.strip() or proc.stdout.strip() or f"exit {proc.returncode}"
            log.error("ns8-sendmail failed: %s", err)
        else:
            log.info("Notification sent: %s -> %s", subject, mail_to)

    except FileNotFoundError:
        # runagent is missing — this host is not an NS8 node, or PATH is wrong.
        log.error("'runagent' not found in PATH — is this an NS8 node?")
    except subprocess.TimeoutExpired:
        log.error("ns8-sendmail timed out after 30s")
    except Exception as e:
        log.error("Failed to send notification: %s", e)