"use client";

import React, { useState, useEffect, useCallback } from "react";
import { Plus, Trash2, RefreshCcw, Check, AlertCircle, ArrowRight, ArrowLeftRight, Pencil, X } from "lucide-react";

interface CalendarSyncRule {
  id: string;
  name: string;
  enabled: boolean;
  direction: "one-way" | "two-way";
  sourceConnectionId: string;
  sourceCalendarId: string;
  targetConnectionId: string;
  targetCalendarId: string;
  syncDescription: boolean;
  syncLocation: boolean;
  syncRecurring: boolean;
  titlePrefix: string;
  lastSyncedAt?: string | null;
}

interface CalendarInfo {
  id: string;
  title: string;
  color?: string;
  editable?: boolean;
}

interface ConnectionInfo {
  id: string;
  provider: string;
  calendars?: CalendarInfo[];
}

interface Props {
  connections: ConnectionInfo[];
  darkMode?: boolean;
  t: Record<string, string>;
}

const PROVIDER_LABELS: Record<string, string> = {
  google: "Google",
  apple: "Apple",
  outlook: "Outlook",
  synology: "Synology",
};

function calendarLabel(conn: ConnectionInfo, calId: string): string {
  const cal = conn.calendars?.find((c) => c.id === calId);
  return cal?.title || calId;
}

function providerLabel(conn: ConnectionInfo): string {
  return PROVIDER_LABELS[conn.provider] || conn.provider;
}

// Flatten all (connectionId, calendarId) pairs for picker usage
function allCalendarOptions(connections: ConnectionInfo[]) {
  const opts: { connId: string; calId: string; label: string; connLabel: string; color?: string }[] = [];
  for (const conn of connections) {
    if (!conn.calendars) continue;
    for (const cal of conn.calendars) {
      opts.push({
        connId: conn.id,
        calId: cal.id,
        label: cal.title,
        connLabel: providerLabel(conn),
        color: cal.color,
      });
    }
  }
  return opts;
}

const EMPTY_FORM = {
  name: "",
  enabled: true,
  direction: "one-way" as "one-way" | "two-way",
  sourceConnectionId: "",
  sourceCalendarId: "",
  targetConnectionId: "",
  targetCalendarId: "",
  syncDescription: true,
  syncLocation: true,
  syncRecurring: false,
  titlePrefix: "",
};

export default function CalendarSyncRulesPanel({ connections, darkMode, t }: Props) {
  const [rules, setRules] = useState<CalendarSyncRule[]>([]);
  const [loading, setLoading] = useState(true);
  const [syncing, setSyncing] = useState(false);
  const [syncResults, setSyncResults] = useState<{ ruleId: string; ruleName: string; created: number; updated: number; deleted: number; error?: string }[] | null>(null);
  const [showForm, setShowForm] = useState(false);
  const [editingId, setEditingId] = useState<string | null>(null);
  const [form, setForm] = useState({ ...EMPTY_FORM });
  const [formError, setFormError] = useState("");
  const [saving, setSaving] = useState(false);
  const [msg, setMsg] = useState<{ text: string; type: "success" | "error" } | null>(null);

  const calOptions = allCalendarOptions(connections);

  const fetchRules = useCallback(async () => {
    try {
      const res = await fetch("/api/calendar/cross-sync/rules");
      const data = await res.json();
      setRules(data.rules || []);
    } catch {
      // silently fail
    } finally {
      setLoading(false);
    }
  }, []);

  useEffect(() => { fetchRules(); }, [fetchRules]);

  const openNewForm = () => {
    setForm({ ...EMPTY_FORM });
    setEditingId(null);
    setFormError("");
    setShowForm(true);
  };

  const openEditForm = (rule: CalendarSyncRule) => {
    setForm({
      name: rule.name,
      enabled: rule.enabled,
      direction: rule.direction,
      sourceConnectionId: rule.sourceConnectionId,
      sourceCalendarId: rule.sourceCalendarId,
      targetConnectionId: rule.targetConnectionId,
      targetCalendarId: rule.targetCalendarId,
      syncDescription: rule.syncDescription,
      syncLocation: rule.syncLocation,
      syncRecurring: rule.syncRecurring,
      titlePrefix: rule.titlePrefix,
    });
    setEditingId(rule.id);
    setFormError("");
    setShowForm(true);
  };

  const closeForm = () => { setShowForm(false); setEditingId(null); };

  const saveForm = async () => {
    if (!form.sourceCalendarId || !form.targetCalendarId) {
      setFormError("Please select a source and target calendar.");
      return;
    }
    if (form.sourceConnectionId === form.targetConnectionId && form.sourceCalendarId === form.targetCalendarId) {
      setFormError("Source and target calendar must be different.");
      return;
    }
    setSaving(true);
    setFormError("");
    try {
      const url = editingId
        ? `/api/calendar/cross-sync/rules/${editingId}`
        : "/api/calendar/cross-sync/rules";
      const method = editingId ? "PATCH" : "POST";
      const res = await fetch(url, {
        method,
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify(form),
      });
      if (!res.ok) {
        const err = await res.json();
        throw new Error(err.error || "Failed to save");
      }
      await fetchRules();
      closeForm();
      setMsg({ text: editingId ? "Rule updated." : "Rule created.", type: "success" });
      setTimeout(() => setMsg(null), 3000);
    } catch (err: any) {
      setFormError(err.message || "Failed to save rule");
    } finally {
      setSaving(false);
    }
  };

  const deleteRule = async (ruleId: string) => {
    if (!confirm("Delete this sync rule? Existing synced events will NOT be removed.")) return;
    try {
      await fetch(`/api/calendar/cross-sync/rules/${ruleId}`, { method: "DELETE" });
      setRules((prev) => prev.filter((r) => r.id !== ruleId));
      setMsg({ text: "Rule deleted.", type: "success" });
      setTimeout(() => setMsg(null), 3000);
    } catch {
      setMsg({ text: "Failed to delete rule.", type: "error" });
      setTimeout(() => setMsg(null), 4000);
    }
  };

  const toggleEnabled = async (rule: CalendarSyncRule) => {
    const newVal = !rule.enabled;
    setRules((prev) => prev.map((r) => r.id === rule.id ? { ...r, enabled: newVal } : r));
    await fetch(`/api/calendar/cross-sync/rules/${rule.id}`, {
      method: "PATCH",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ enabled: newVal }),
    });
  };

  const runSync = async () => {
    setSyncing(true);
    setSyncResults(null);
    try {
      const res = await fetch("/api/calendar/cross-sync/run", { method: "POST" });
      const data = await res.json();
      setSyncResults(data.results || []);
    } catch {
      setMsg({ text: "Sync failed.", type: "error" });
      setTimeout(() => setMsg(null), 4000);
    } finally {
      setSyncing(false);
    }
  };

  // Derive connection for a given connectionId
  const connFor = (id: string) => connections.find((c) => c.id === id);

  const label = (s: string) => (
    <label style={{ fontSize: "0.8rem", fontWeight: 600, color: "var(--weekly-settings-label)", display: "block", marginBottom: "4px" }}>
      {s}
    </label>
  );

  const inputStyle: React.CSSProperties = {
    width: "100%", padding: "7px 10px", borderRadius: "7px",
    border: "1px solid var(--weekly-border, #e5e7eb)",
    background: "var(--weekly-input-bg, var(--weekly-bg, #fff))",
    color: "var(--weekly-text, #333)", fontSize: "0.875rem",
  };

  const btnStyle = (primary?: boolean): React.CSSProperties => ({
    padding: "8px 16px", borderRadius: "8px",
    background: primary ? "var(--weekly-text, #333)" : "var(--weekly-bg, #fff)",
    color: primary ? "var(--weekly-bg, #fff)" : "var(--weekly-text, #333)",
    border: primary ? "none" : "1px solid var(--weekly-border, #e5e7eb)",
    fontSize: "0.875rem", fontWeight: 500, cursor: "pointer",
    display: "flex", alignItems: "center", gap: "6px",
  });

  // Calendar picker select for the form
  const CalPicker = ({ label: pickerLabel, connId, calId, onChange }: {
    label: string;
    connId: string;
    calId: string;
    onChange: (connId: string, calId: string) => void;
  }) => {
    const value = connId && calId ? `${connId}::${calId}` : "";
    return (
      <div style={{ marginBottom: "12px" }}>
        {label(pickerLabel)}
        <select
          value={value}
          onChange={(e) => {
            const [cid, calid] = e.target.value.split("::");
            onChange(cid, calid);
          }}
          style={inputStyle}
        >
          <option value="">— Select calendar —</option>
          {calOptions.map((opt) => (
            <option key={`${opt.connId}::${opt.calId}`} value={`${opt.connId}::${opt.calId}`}>
              [{opt.connLabel}] {opt.label}
            </option>
          ))}
        </select>
      </div>
    );
  };

  if (loading) return <p style={{ opacity: 0.5, fontSize: "0.875rem" }}>Loading sync rules…</p>;

  return (
    <div style={{ display: "flex", flexDirection: "column", gap: "16px" }}>
      {/* Enable/Disable section header */}
      <div style={{ display: "flex", alignItems: "center", justifyContent: "space-between", paddingBottom: "12px", borderBottom: "1px solid var(--weekly-border, #e5e7eb)" }}>
        <div>
          <h3 style={{ fontSize: "1rem", fontWeight: 700, marginBottom: "2px" }}>
            {t.calendarSyncTitle || "Calendar Sync"}
          </h3>
          <p style={{ fontSize: "0.8rem", color: "var(--weekly-text-light, #888)", margin: 0 }}>
            {t.calendarSyncDesc || "Sync events between connected calendar providers."}
          </p>
        </div>
        <button
          onClick={runSync}
          disabled={syncing || rules.filter((r) => r.enabled).length === 0}
          style={{
            ...btnStyle(),
            opacity: syncing || rules.filter((r) => r.enabled).length === 0 ? 0.4 : 1,
          }}
          title={t.syncNow || "Sync Now"}
        >
          <RefreshCcw size={15} style={syncing ? { animation: "spin 1s linear infinite" } : {}} />
          {syncing ? (t.syncing || "Syncing…") : (t.syncNow || "Sync Now")}
        </button>
      </div>

      {/* Status message */}
      {msg && (
        <div style={{
          padding: "8px 12px", borderRadius: "7px", fontSize: "0.85rem",
          background: msg.type === "success" ? "rgba(16,185,129,0.1)" : "rgba(239,68,68,0.1)",
          color: msg.type === "success" ? "#059669" : "#dc2626",
          border: `1px solid ${msg.type === "success" ? "#10b981" : "#ef4444"}`,
          display: "flex", alignItems: "center", gap: "6px",
        }}>
          {msg.type === "success" ? <Check size={14} /> : <AlertCircle size={14} />}
          {msg.text}
        </div>
      )}

      {/* Sync results */}
      {syncResults && (
        <div style={{ padding: "10px 12px", borderRadius: "8px", border: "1px solid var(--weekly-border, #e5e7eb)", background: "var(--weekly-hover, #f9fafb)", fontSize: "0.8rem" }}>
          <strong style={{ display: "block", marginBottom: "6px" }}>{t.syncResults || "Sync Results"}</strong>
          {syncResults.length === 0
            ? <span style={{ opacity: 0.5 }}>{t.noRulesEnabled || "No enabled rules found."}</span>
            : syncResults.map((r) => (
              <div key={r.ruleId} style={{ marginBottom: "4px", display: "flex", gap: "8px", flexWrap: "wrap" }}>
                <span style={{ fontWeight: 600 }}>{r.ruleName || "Rule"}</span>
                {r.error
                  ? <span style={{ color: "#dc2626" }}>Error: {r.error}</span>
                  : <>
                    {r.created > 0 && <span style={{ color: "#059669" }}>+{r.created}</span>}
                    {r.updated > 0 && <span style={{ color: "#0ea5e9" }}>~{r.updated}</span>}
                    {r.deleted > 0 && <span style={{ color: "#f59e0b" }}>−{r.deleted}</span>}
                    {r.created === 0 && r.updated === 0 && r.deleted === 0 && <span style={{ opacity: 0.5 }}>up to date</span>}
                  </>
                }
              </div>
            ))
          }
        </div>
      )}

      {/* No connections warning */}
      {connections.length < 2 && (
        <div style={{ padding: "10px 12px", borderRadius: "8px", background: "rgba(245,158,11,0.08)", border: "1px solid #f59e0b", fontSize: "0.85rem", color: "#b45309" }}>
          <AlertCircle size={14} style={{ display: "inline", marginRight: "6px" }} />
          {t.syncNeedsTwo || "You need at least two connected calendars to create a sync rule."}
        </div>
      )}

      {/* Rules list */}
      {rules.length > 0 && (
        <div style={{ display: "flex", flexDirection: "column", gap: "8px" }}>
          {rules.map((rule) => {
            const srcConn = connFor(rule.sourceConnectionId);
            const tgtConn = connFor(rule.targetConnectionId);
            return (
              <div key={rule.id} style={{
                padding: "12px 14px", borderRadius: "10px",
                border: "1px solid var(--weekly-border, #e5e7eb)",
                background: "var(--weekly-bg, #fff)",
                display: "flex", flexDirection: "column", gap: "6px",
              }}>
                <div style={{ display: "flex", alignItems: "center", justifyContent: "space-between", gap: "8px" }}>
                  <div style={{ display: "flex", alignItems: "center", gap: "8px", flex: 1, minWidth: 0 }}>
                    {/* Toggle */}
                    <button
                      onClick={() => toggleEnabled(rule)}
                      title={rule.enabled ? "Disable" : "Enable"}
                      style={{
                        width: "34px", height: "20px", borderRadius: "10px", border: "none",
                        background: rule.enabled ? "#22c55e" : "#d1d5db",
                        position: "relative", cursor: "pointer", flexShrink: 0, transition: "background 0.2s",
                      }}
                    >
                      <span style={{
                        position: "absolute", top: "3px",
                        left: rule.enabled ? "17px" : "3px",
                        width: "14px", height: "14px", borderRadius: "50%",
                        background: "#fff", transition: "left 0.2s",
                      }} />
                    </button>
                    <div style={{ minWidth: 0 }}>
                      <div style={{ fontWeight: 600, fontSize: "0.875rem", overflow: "hidden", textOverflow: "ellipsis", whiteSpace: "nowrap" }}>
                        {rule.name || `${srcConn ? providerLabel(srcConn) : "?"} → ${tgtConn ? providerLabel(tgtConn) : "?"}`}
                      </div>
                      <div style={{ fontSize: "0.75rem", color: "var(--weekly-text-light, #888)", display: "flex", alignItems: "center", gap: "4px", marginTop: "2px" }}>
                        <span>{srcConn ? calendarLabel(srcConn, rule.sourceCalendarId) : rule.sourceCalendarId}</span>
                        {rule.direction === "two-way" ? <ArrowLeftRight size={11} /> : <ArrowRight size={11} />}
                        <span>{tgtConn ? calendarLabel(tgtConn, rule.targetCalendarId) : rule.targetCalendarId}</span>
                      </div>
                    </div>
                  </div>
                  <div style={{ display: "flex", gap: "4px", flexShrink: 0 }}>
                    <button onClick={() => openEditForm(rule)} style={{ background: "none", border: "none", cursor: "pointer", color: "var(--weekly-text-light, #888)", padding: "4px" }} title="Edit">
                      <Pencil size={14} />
                    </button>
                    <button onClick={() => deleteRule(rule.id)} style={{ background: "none", border: "none", cursor: "pointer", color: "#ef4444", padding: "4px" }} title="Delete">
                      <Trash2 size={14} />
                    </button>
                  </div>
                </div>
                {rule.lastSyncedAt && (
                  <div style={{ fontSize: "0.7rem", color: "var(--weekly-text-light, #aaa)" }}>
                    Last synced: {new Date(rule.lastSyncedAt).toLocaleString()}
                  </div>
                )}
              </div>
            );
          })}
        </div>
      )}

      {rules.length === 0 && !showForm && (
        <p style={{ opacity: 0.5, fontSize: "0.875rem", textAlign: "center", padding: "16px 0" }}>
          {t.noSyncRules || "No sync rules yet. Add one below."}
        </p>
      )}

      {/* Add new rule button */}
      {!showForm && connections.length >= 2 && (
        <button onClick={openNewForm} style={{ ...btnStyle(), justifyContent: "center", padding: "10px 16px" }}>
          <Plus size={15} />
          {t.addSyncRule || "Add Sync Rule"}
        </button>
      )}

      {/* Form */}
      {showForm && (
        <div style={{
          padding: "16px", borderRadius: "12px",
          border: "1px solid var(--weekly-border, #e5e7eb)",
          background: "var(--weekly-hover, #f9fafb)",
          display: "flex", flexDirection: "column", gap: "8px",
        }}>
          <div style={{ display: "flex", alignItems: "center", justifyContent: "space-between", marginBottom: "4px" }}>
            <strong style={{ fontSize: "0.9rem" }}>{editingId ? (t.editSyncRule || "Edit Rule") : (t.newSyncRule || "New Sync Rule")}</strong>
            <button onClick={closeForm} style={{ background: "none", border: "none", cursor: "pointer", color: "var(--weekly-text-light, #888)" }}>
              <X size={16} />
            </button>
          </div>

          {/* Rule name */}
          <div>
            {label(t.syncRuleName || "Rule Name (optional)")}
            <input
              type="text"
              value={form.name}
              onChange={(e) => setForm({ ...form, name: e.target.value })}
              placeholder={t.syncRuleNamePlaceholder || "e.g. Work → Personal"}
              style={inputStyle}
            />
          </div>

          {/* Direction */}
          <div style={{ marginBottom: "4px" }}>
            {label(t.syncDirection || "Direction")}
            <div style={{ display: "flex", gap: "8px" }}>
              {(["one-way", "two-way"] as const).map((d) => (
                <button
                  key={d}
                  onClick={() => setForm({ ...form, direction: d })}
                  style={{
                    ...btnStyle(form.direction === d),
                    flex: 1, justifyContent: "center",
                  }}
                >
                  {d === "one-way" ? <><ArrowRight size={14} /> {t.oneWay || "One-way"}</> : <><ArrowLeftRight size={14} /> {t.twoWay || "Two-way"}</>}
                </button>
              ))}
            </div>
          </div>

          {/* Source calendar */}
          <CalPicker
            label={t.sourceCalendar || "Source Calendar"}
            connId={form.sourceConnectionId}
            calId={form.sourceCalendarId}
            onChange={(connId, calId) => setForm({ ...form, sourceConnectionId: connId, sourceCalendarId: calId })}
          />

          {/* Target calendar */}
          <CalPicker
            label={t.targetCalendar || "Target Calendar"}
            connId={form.targetConnectionId}
            calId={form.targetCalendarId}
            onChange={(connId, calId) => setForm({ ...form, targetConnectionId: connId, targetCalendarId: calId })}
          />

          {/* Title prefix */}
          <div>
            {label(t.titlePrefix || "Title Prefix (optional)")}
            <input
              type="text"
              value={form.titlePrefix}
              onChange={(e) => setForm({ ...form, titlePrefix: e.target.value })}
              placeholder={t.titlePrefixPlaceholder || "e.g. [Work] "}
              style={inputStyle}
            />
          </div>

          {/* Options checkboxes */}
          <div style={{ display: "flex", flexDirection: "column", gap: "6px", marginTop: "4px" }}>
            {([
              { key: "syncDescription", label: t.syncDescription || "Sync description" },
              { key: "syncLocation", label: t.syncLocation || "Sync location" },
              { key: "syncRecurring", label: t.syncRecurring || "Include recurring events" },
            ] as const).map(({ key, label: optLabel }) => (
              <label key={key} style={{ display: "flex", alignItems: "center", gap: "8px", fontSize: "0.875rem", cursor: "pointer" }}>
                <input
                  type="checkbox"
                  checked={form[key]}
                  onChange={(e) => setForm({ ...form, [key]: e.target.checked })}
                  style={{ width: "15px", height: "15px" }}
                />
                {optLabel}
              </label>
            ))}
          </div>

          {formError && (
            <div style={{ fontSize: "0.8rem", color: "#dc2626", display: "flex", alignItems: "center", gap: "6px" }}>
              <AlertCircle size={13} /> {formError}
            </div>
          )}

          <div style={{ display: "flex", gap: "8px", marginTop: "4px" }}>
            <button onClick={saveForm} disabled={saving} style={{ ...btnStyle(true), flex: 1, justifyContent: "center", opacity: saving ? 0.6 : 1 }}>
              {saving ? (t.saving || "Saving…") : (editingId ? (t.updateRule || "Update Rule") : (t.createRule || "Create Rule"))}
            </button>
            <button onClick={closeForm} style={{ ...btnStyle(), flexShrink: 0 }}>
              {t.cancel || "Cancel"}
            </button>
          </div>
        </div>
      )}
    </div>
  );
}