from __future__ import annotations

from collections.abc import Mapping, Sequence
from dataclasses import dataclass
from datetime import datetime
from urllib.parse import urlencode

from ..security import admin_csrf_token
from ..settings import DdnsSettings
from ..store import DdnsStore
from .html_utils import SafeHtml, attr, escape, trusted
from .layout import PageOptions, _page, _top_nav
from .templates_admin_tables import (
    _account_row,
    _admin_table_pagination,
    _admin_table_toolbar,
    _event_row,
)


@dataclass(frozen=True)
class _CleanupSummary:
    last_run: object
    next_run: object
    status: object
    last_error: object
    interval_seconds: object
    accounts_removed: object


@dataclass(frozen=True)
class AdminPageContext:
    accounts: Sequence[Mapping[str, object]]
    cleanup_runs: Sequence[Mapping[str, object]]
    scheduled_tasks: Sequence[Mapping[str, object]]
    update_events: Sequence[Mapping[str, object]]
    service_metrics: dict[str, float]
    table_counts: dict[str, int]
    table_offsets: dict[str, int]
    table_limit: int
    notice_html: SafeHtml | None


def _admin_page_context(
    store: DdnsStore,
    table_offsets: dict[str, int],
    table_limit: int,
    notice_html: SafeHtml | None,
) -> AdminPageContext:
    return AdminPageContext(
        accounts=store.list_accounts(limit=table_limit, offset=table_offsets.get("accounts", 0)),
        cleanup_runs=store.list_cleanup_runs(limit=table_limit, offset=table_offsets.get("cleanup_runs", 0)),
        scheduled_tasks=store.list_scheduled_tasks(),
        update_events=store.list_update_events(table_limit, offset=table_offsets.get("update_events", 0)),
        service_metrics=store.get_service_metrics(),
        table_counts={
            "accounts": store.count_accounts(),
            "cleanup_runs": store.count_cleanup_runs(),
            "update_events": store.count_update_events(),
        },
        table_offsets=table_offsets,
        table_limit=table_limit,
        notice_html=notice_html,
    )


def _admin_secret_panel(title: str, rows: list[SafeHtml]) -> SafeHtml:
    return trusted(f"""
    <section class="section success-section">
      <div class="container">
        <p class="eyebrow">Admin action</p>
        <h2>{escape(title)}</h2>
        <p class="section-copy">Copy these values now. Secret values are only shown once.</p>
        <div class="d-grid gap-2">
          {"".join(rows)}
        </div>
      </div>
    </section>
    """)


def _render_admin_page(
    settings: DdnsSettings,
    context: AdminPageContext,
) -> str:
    csrf = attr(admin_csrf_token(settings))
    admin_path = settings.admin_path
    safe_admin_path = attr(admin_path)
    rows = _account_rows(context.accounts, csrf=csrf, admin_path=admin_path)
    event_rows = _event_rows(context.update_events)
    accounts_count = escape(context.table_counts.get("accounts", len(context.accounts)))
    event_count = escape(context.table_counts.get("update_events", len(context.update_events)))
    metrics_html = _metrics_panel(context.service_metrics)
    account_pager = _server_page_links(
        admin_path,
        "accounts_offset",
        context.table_offsets.get("accounts", 0),
        context.table_limit,
        context.table_counts.get("accounts", 0),
    )
    event_pager = _server_page_links(
        admin_path,
        "update_events_offset",
        context.table_offsets.get("update_events", 0),
        context.table_limit,
        context.table_counts.get("update_events", 0),
    )
    cleanup_panel = _cleanup_panel(settings, context.cleanup_runs, context.scheduled_tasks, safe_admin_path, csrf)
    totals_html = _totals_strip(context.table_counts, context.service_metrics)
    title_section = _admin_title_section(totals_html)
    status_section = _admin_status_section(cleanup_panel, metrics_html)
    hostnames_section = _admin_hostnames_section(context, rows, accounts_count, account_pager)
    events_section = _admin_events_section(context, event_rows, event_count, event_pager)
    return _page(
        "KarlDNS Admin",
        trusted(f"""
        <main id="main">
          {_top_nav("Operator")}
          {title_section}
          {context.notice_html or ""}
          {status_section}
          {hostnames_section}
          {events_section}
        </main>
        """),
        PageOptions(
            extra_styles=trusted('<link href="/admin.css?v=5" rel="stylesheet">'),
            extra_scripts=trusted('<script src="/admin-tables.js?v=3" defer></script>'),
        ),
    )


def _admin_title_section(totals_html: SafeHtml) -> SafeHtml:
    return trusted(f"""
      <section class="admin-console">
        <div class="container">
          <div class="admin-page-title">
            <div>
              <p class="eyebrow">KarlDNS</p>
              <h1>Operator console</h1>
            </div>
            {totals_html}
          </div>
        </div>
      </section>
    """)


def _admin_status_section(cleanup_panel: SafeHtml, metrics_html: SafeHtml) -> SafeHtml:
    return trusted(f"""
      <section class="admin-block">
        <div class="container">
          {cleanup_panel}
          {metrics_html}
        </div>
      </section>
    """)


def _admin_hostnames_section(
    context: AdminPageContext,
    rows: SafeHtml,
    accounts_count: str,
    account_pager: SafeHtml,
) -> SafeHtml:
    return trusted(f"""
      <section class="admin-block">
        <div class="container">
          <div class="admin-section-heading">
            <div>
              <h2>Hostnames</h2>
              <p class="section-copy mb-0">{escape(len(context.accounts))} of {accounts_count} shown.</p>
            </div>
          </div>
          {_admin_table_toolbar("hostnames", "Filter visible hostnames")}
          <div class="table-responsive border rounded admin-table-scroll" data-slot="card">
            <table class="table mb-0">
              <thead>
                <tr>
                  <th scope="col">Hostname</th>
                  <th scope="col">Status</th>
                  <th scope="col">IPv4</th>
                  <th scope="col">IPv6</th>
                  <th scope="col">Updated</th>
                  <th scope="col">Links</th>
                  <th scope="col">Actions</th>
                </tr>
              </thead>
              <tbody>{rows}</tbody>
            </table>
          </div>
          {_admin_table_pagination()}
          {account_pager}
        </div>
      </section>
    """)


def _admin_events_section(
    context: AdminPageContext,
    event_rows: SafeHtml,
    event_count: str,
    event_pager: SafeHtml,
) -> SafeHtml:
    return trusted(f"""
      <section class="admin-block">
        <div class="container">
          <div class="admin-section-heading">
            <div>
              <h2>Update events</h2>
              <p class="section-copy mb-0">
                {escape(len(context.update_events))} of {event_count} shown. Unchanged checks are grouped.
              </p>
            </div>
          </div>
          {_admin_table_toolbar("update-events", "Filter visible update events")}
          <div class="table-responsive border rounded admin-table-scroll" data-slot="card">
            <table class="table mb-0">
              <thead>
                <tr>
                  <th scope="col">Time</th>
                  <th scope="col">Hostname</th>
                  <th scope="col">Status</th>
                  <th scope="col">IPv4</th>
                  <th scope="col">IPv6</th>
                  <th scope="col">Count</th>
                  <th scope="col">Detail</th>
                </tr>
              </thead>
              <tbody>{event_rows}</tbody>
            </table>
          </div>
          {_admin_table_pagination()}
          {event_pager}
        </div>
      </section>
    """)


def _account_rows(accounts: Sequence[Mapping[str, object]], *, csrf: str, admin_path: str) -> SafeHtml:
    return trusted("\n".join(_account_row(account, csrf=csrf, admin_path=admin_path) for account in accounts) or """
      <tr class="empty-row">
        <td colspan="7" class="empty">
          <div class="empty-state">
            <div class="empty-state-title">No hostnames yet.</div>
            <div class="empty-state-description">
              Generated hostnames appear here after users create or register them.
            </div>
          </div>
        </td>
      </tr>
    """)


def _event_rows(events: Sequence[Mapping[str, object]]) -> SafeHtml:
    return trusted("\n".join(_event_row(event) for event in events) or """
      <tr class="empty-row">
        <td colspan="7" class="empty">
          <div class="empty-state">
            <div class="empty-state-title">No update events yet.</div>
            <div class="empty-state-description">
              Router update activity and DNS publish results will appear here.
            </div>
          </div>
        </td>
      </tr>
    """)


def _totals_strip(table_counts: dict[str, int], metrics: dict[str, float]) -> SafeHtml:
    items = [
        ("Hostnames", table_counts.get("accounts", 0)),
        ("Events", table_counts.get("update_events", 0)),
        ("DNS failures", int(metrics.get("dns_failures_total", 0))),
        ("Blocked", int(metrics.get("rate_limit_hits_total", 0))),
    ]
    return trusted(
        '<div class="admin-total-strip" aria-label="Service totals">'
        + "".join(f"<span><strong>{escape(value)}</strong>{escape(label)}</span>" for label, value in items)
        + "</div>"
    )


def _admin_notice(kind: str, message: str) -> SafeHtml:
    alert_class = "alert-success" if kind == "success" else "alert-info"
    return trusted(f"""
      <div class="container">
        <div class="alert {alert_class} ui-alert admin-notice" role="status" data-slot="alert">{escape(message)}</div>
      </div>
    """)


def _server_page_links(admin_path: str, offset_name: str, offset: int, limit: int, total: int) -> SafeHtml:
    if total <= limit:
        return trusted("")
    previous_offset = max(0, offset - limit)
    next_offset = offset + limit
    previous_disabled = " disabled" if offset <= 0 else ""
    next_disabled = " disabled" if next_offset >= total else ""
    previous_href = attr(f"{admin_path}?{urlencode({offset_name: previous_offset})}")
    next_href = attr(f"{admin_path}?{urlencode({offset_name: next_offset})}")
    start = min(offset + 1, total)
    end = min(offset + limit, total)
    return trusted(f"""
      <nav class="d-flex align-items-center justify-content-end gap-2 mt-2" aria-label="Server-side table pages">
        <span class="small text-secondary">{escape(start)}-{escape(end)} of {escape(total)}</span>
        <a class="btn btn-sm btn-light rounded-pill{previous_disabled}" href="{previous_href}"
          aria-disabled="{str(offset <= 0).lower()}">Previous</a>
        <a class="btn btn-sm btn-light rounded-pill{next_disabled}" href="{next_href}"
          aria-disabled="{str(next_offset >= total).lower()}">Next</a>
      </nav>
    """)


def _cleanup_panel(
    settings: DdnsSettings,
    cleanup_runs: Sequence[Mapping[str, object]],
    scheduled_tasks: Sequence[Mapping[str, object]],
    safe_admin_path: str,
    csrf: str,
) -> SafeHtml:
    summary = _cleanup_summary(
        cleanup_runs=cleanup_runs,
        scheduled_tasks=scheduled_tasks,
        fallback_interval_seconds=settings.cleanup_interval_seconds,
    )
    error_html = (
        trusted(f'<p class="small text-danger mb-0">Last error: {escape(summary.last_error)}</p>')
        if summary.last_error
        else trusted("")
    )
    last_run_title = attr(str(summary.last_run or "Never"))
    next_run_title = attr(str(summary.next_run or "Pending"))
    last_run_display = escape(_format_timestamp(summary.last_run, "Never"))
    next_run_display = escape(_format_timestamp(summary.next_run, "Pending"))
    return trusted(f"""
      <div class="admin-cleanup-bar">
        <div class="admin-cleanup-title">
          <h2>Cleanup</h2>
          <span>Every {escape(_format_interval(summary.interval_seconds))}</span>
        </div>
        <dl class="admin-cleanup-times">
          <div><dt>Last run</dt><dd title="{last_run_title}">{last_run_display}</dd></div>
          <div><dt>Next run</dt><dd title="{next_run_title}">{next_run_display}</dd></div>
          <div><dt>Status</dt><dd>{escape(str(summary.status))}</dd></div>
          <div><dt>Removed</dt><dd>{escape(summary.accounts_removed)}</dd></div>
        </dl>
        {error_html}
        <form method="post" action="{safe_admin_path}/cleanup" aria-label="Run cleanup now">
          <input type="hidden" name="csrf" value="{csrf}">
          <button type="submit" class="btn btn-primary rounded-pill">Run now</button>
        </form>
      </div>
    """)


def _cleanup_task(scheduled_tasks: Sequence[Mapping[str, object]]) -> Mapping[str, object]:
    return next(
        (item for item in scheduled_tasks if item.get("name") == "cleanup"),
        scheduled_tasks[0] if scheduled_tasks else {},
    )


def _cleanup_summary(
    *,
    cleanup_runs: Sequence[Mapping[str, object]],
    scheduled_tasks: Sequence[Mapping[str, object]],
    fallback_interval_seconds: int,
) -> _CleanupSummary:
    task = _cleanup_task(scheduled_tasks)
    last_cleanup = cleanup_runs[0] if cleanup_runs else {}
    return _CleanupSummary(
        last_run=_cleanup_last_run(task, last_cleanup),
        next_run=task.get("next_run_at"),
        status=task.get("last_status") or "pending",
        last_error=task.get("last_error") or "",
        interval_seconds=task.get("interval_seconds") or fallback_interval_seconds,
        accounts_removed=_cleanup_accounts_removed(last_cleanup),
    )


def _cleanup_last_run(task: Mapping[str, object], last_cleanup: Mapping[str, object]) -> object:
    return task.get("last_finished_at") or last_cleanup.get("created_at")


def _cleanup_accounts_removed(last_cleanup: Mapping[str, object]) -> object:
    return last_cleanup.get("unused_accounts_deleted", 0)


def _metrics_panel(metrics: dict[str, float]) -> SafeHtml:
    samples = metrics.get("update_latency_samples_total", 0)
    average_latency = metrics.get("update_latency_ms_total", 0) / samples if samples else 0
    items = [
        ("Updates", _metric_int(metrics.get("update_requests_total", 0))),
        ("Updated", _metric_int(metrics.get("update_success_total", 0))),
        ("DNS failures", _metric_int(metrics.get("dns_failures_total", 0))),
        ("DNS check failures", _metric_int(metrics.get("dns_reconcile_failures_total", 0))),
        ("Blocked requests", _metric_int(metrics.get("rate_limit_hits_total", 0))),
        ("Average update time", f"{average_latency:.1f} ms"),
        ("Last update time", f"{metrics.get('last_update_latency_ms', 0):.1f} ms"),
        (
            "Cleanup ok/errors",
            (
                f"{_metric_int(metrics.get('cleanup_success_total', 0))}/"
                f"{_metric_int(metrics.get('cleanup_errors_total', 0))}"
            ),
        ),
    ]
    cards = "\n".join(f"""
        <span><strong>{escape(value)}</strong>{escape(label)}</span>
        """ for label, value in items)
    return trusted(f"""
      <div class="admin-metric-strip" aria-label="Service metrics">
        {cards}
      </div>
    """)


def _metric_int(value: object) -> str:
    try:
        return str(int(float(str(value))))
    except ValueError:
        return "0"


def _format_interval(seconds: object) -> str:
    try:
        value = int(str(seconds))
    except (TypeError, ValueError):
        return str(seconds)
    if value % 3600 == 0:
        hours = value // 3600
        return f"{hours}h"
    if value % 60 == 0:
        minutes = value // 60
        return f"{minutes}m"
    return f"{value}s"


def _format_timestamp(value: object, fallback: str = "-") -> str:
    if not value:
        return fallback
    raw = str(value)
    try:
        parsed = datetime.fromisoformat(raw)
    except ValueError:
        return raw
    return parsed.strftime("%Y-%m-%d %H:%M")