import React, { useCallback, useEffect, useMemo, useState } from 'react';
import {
    ArrowLeft,
    ClipboardCopy,
    Loader2,
    ShieldAlert,
    Link2,
    Sparkles,
    UserPlus,
    Users,
    Trash2,
} from 'lucide-react';
import AppShell from '@/components/layout/AppShell';
import EmailGeneratorTab from '@/components/campaigns/EmailGeneratorTab';
import LinkedInConnectSettings from '@/components/settings/LinkedInConnectSettings';
import ConnectMailboxSettings from '@/components/settings/ConnectMailboxSettings';
import { Button } from '@/components/ui/button';
import { Input } from '@/components/ui/input';
import {
    Select,
    SelectContent,
    SelectItem,
    SelectTrigger,
    SelectValue,
} from '@/components/ui/select';
import { apiFetch } from '@/lib/api';
import { cn } from '@/lib/utils';

export default function Settings() {
    /** 'main' | 'email_generator' — full-page generator inside Settings */
    const [settingsPanel, setSettingsPanel] = useState('main');
    const [me, setMe] = useState(null);
    const [meLoading, setMeLoading] = useState(true);
    const [members, setMembers] = useState([]);
    const [membersLoading, setMembersLoading] = useState(true);
    const [membersError, setMembersError] = useState('');

    const [inviteEmail, setInviteEmail] = useState('');
    const [inviteBusy, setInviteBusy] = useState(false);
    const [inviteResult, setInviteResult] = useState(null);

    /** e.g. `member:12` or `invite:3` while a remove/revoke request is in flight */
    const [removeBusyKey, setRemoveBusyKey] = useState(null);

    const loadMe = useCallback(async () => {
        setMeLoading(true);
        try {
            const r = await apiFetch('/api/auth/me');
            setMe(r.ok ? await r.json() : null);
        } catch {
            setMe(null);
        } finally {
            setMeLoading(false);
        }
    }, []);

    const loadMembers = useCallback(async () => {
        setMembersLoading(true);
        setMembersError('');
        try {
            const r = await apiFetch('/api/tenants/members');
            if (!r.ok) {
                const data = await r.json().catch(() => ({}));
                setMembersError(
                    typeof data.detail === 'string' ? data.detail : 'Could not load members'
                );
                setMembers([]);
                return;
            }
            const data = await r.json();
            setMembers(data.members || []);
        } catch (e) {
            setMembersError(String(e));
            setMembers([]);
        } finally {
            setMembersLoading(false);
        }
    }, []);

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

    const isAdmin = me?.current_role === 'admin';

    useEffect(() => {
        if (!meLoading && isAdmin) {
            loadMembers();
        }
    }, [meLoading, isAdmin, loadMembers]);

    const webhookUrl = useMemo(() => {
        if (typeof window === 'undefined') return '';
        const base = `${window.location.origin}/api/webhooks/smartlead`;
        const tid = me?.current_tenant_id;
        if (tid != null && !Number.isNaN(Number(tid))) {
            return `${base}?tenant_id=${tid}`;
        }
        return base;
    }, [me]);

    const tenants = me?.tenants || [];
    const multiWorkspace = tenants.length > 1;

    const switchTenant = async (tid) => {
        const id = parseInt(tid, 10);
        if (!id || id === me?.current_tenant_id) return;
        try {
            const res = await apiFetch('/api/auth/switch-tenant', {
                method: 'POST',
                headers: { 'Content-Type': 'application/json' },
                body: JSON.stringify({ tenant_id: id }),
            });
            if (!res.ok) return;
            window.location.reload();
        } catch (e) {
            console.error(e);
        }
    };

    const sendInvite = async () => {
        const email = inviteEmail.trim().toLowerCase();
        if (!email || !email.includes('@')) return;
        setInviteBusy(true);
        setInviteResult(null);
        try {
            const res = await apiFetch('/api/tenants/invite', {
                method: 'POST',
                headers: { 'Content-Type': 'application/json' },
                body: JSON.stringify({ email, role: 'member' }),
            });
            const data = await res.json().catch(() => ({}));
            if (!res.ok) {
                setInviteResult({
                    error: typeof data.detail === 'string' ? data.detail : 'Invite failed',
                });
                return;
            }
            setInviteResult({
                url: data.invite_url,
                emailSent: !!data.email_sent,
                emailError: data.email_error || null,
                inviteeEmail: data.email,
            });
            setInviteEmail('');
            loadMe();
            await loadMembers();
        } catch (e) {
            setInviteResult({ error: String(e) });
        } finally {
            setInviteBusy(false);
        }
    };

    const removeMember = async (userId) => {
        if (!window.confirm('Remove this user from the workspace?')) return;
        setRemoveBusyKey(`member:${userId}`);
        try {
            const res = await apiFetch(`/api/tenants/members/${userId}`, { method: 'DELETE' });
            const data = await res.json().catch(() => ({}));
            if (!res.ok) {
                alert(typeof data.detail === 'string' ? data.detail : 'Could not remove member');
                return;
            }
            await loadMembers();
        } catch (e) {
            alert(e.message || 'Could not remove member');
        } finally {
            setRemoveBusyKey(null);
        }
    };

    const revokeInvitation = async (invitationId) => {
        if (!window.confirm('Cancel this invitation? They will not be able to join with the current link.'))
            return;
        setRemoveBusyKey(`invite:${invitationId}`);
        try {
            const res = await apiFetch(`/api/tenants/invitations/${invitationId}`, { method: 'DELETE' });
            const data = await res.json().catch(() => ({}));
            if (!res.ok) {
                alert(typeof data.detail === 'string' ? data.detail : 'Could not cancel invitation');
                return;
            }
            await loadMembers();
        } catch (e) {
            alert(e.message || 'Could not cancel invitation');
        } finally {
            setRemoveBusyKey(null);
        }
    };

    if (meLoading) {
        return (
            <AppShell title="Settings">
                <div className="flex justify-center py-24 text-slate-500">
                    <Loader2 className="h-10 w-10 animate-spin" />
                </div>
            </AppShell>
        );
    }

    if (!me) {
        return (
            <AppShell title="Settings">
                <div className="rounded-2xl border border-slate-200 bg-white p-8 text-center shadow-sm">
                    <p className="text-slate-600 mb-4">Sign in to manage workspace settings.</p>
                    <Button asChild variant="default">
                        <a href="/api/auth/google">Sign in with Google</a>
                    </Button>
                </div>
            </AppShell>
        );
    }

    if (settingsPanel === 'email_generator') {
        return (
            <AppShell
                title="Settings"
                subtitle="Email / AI generator — upload contacts, prompts, and export."
            >
                <div className="w-full max-w-6xl">
                    <div className="mb-6 flex flex-wrap items-center gap-3">
                        <Button
                            type="button"
                            variant="outline"
                            className="gap-2"
                            onClick={() => setSettingsPanel('main')}
                        >
                            <ArrowLeft className="h-4 w-4" aria-hidden />
                            Back to settings
                        </Button>
                    </div>
                    <EmailGeneratorTab />
                </div>
            </AppShell>
        );
    }

    return (
        <AppShell
            title="Settings"
            subtitle={
                isAdmin
                    ? 'Invitations, members, LinkedIn, mailbox, Smartlead webhook, and email generator.'
                    : 'LinkedIn, mailbox, Smartlead webhook, and email generator. Invites and member management require admin.'
            }
        >
            <div className="space-y-8 max-w-3xl">
                {!isAdmin ? (
                    <div className="rounded-2xl border border-slate-200 bg-slate-50/80 p-5 flex gap-3 items-start">
                        <ShieldAlert className="h-6 w-6 shrink-0 text-slate-500 mt-0.5" />
                        <p className="text-sm text-slate-600">
                            Inviting users and removing members is limited to workspace admins. Ask an
                            admin if you need help.
                        </p>
                    </div>
                ) : null}

                {isAdmin ? (
                <section className="rounded-2xl border border-slate-200 bg-white p-6 shadow-sm">
                    <div className="flex items-center gap-2 text-slate-800 font-semibold mb-2">
                        <UserPlus className="h-5 w-5 text-violet-600" />
                        Invite people
                    </div>
                    <p className="text-sm text-slate-600 mb-4">
                        We email an invitation from your Google account. The invitee must sign in with the
                        same email address.
                    </p>
                    {me?.gmail_invites_ready === false ? (
                        <p className="text-xs text-amber-900 bg-amber-50 border border-amber-200 rounded-lg px-3 py-2 mb-4">
                            Sign in with Google again (you will see a consent screen) so invites can send from your
                            address, or use{' '}
                            <a
                                href="/api/auth/google?reauth_gmail=1"
                                className="font-medium text-violet-700 underline"
                            >
                                Reconnect Google for invites
                            </a>
                            .
                        </p>
                    ) : null}
                    <div className="flex flex-col sm:flex-row gap-2 max-w-xl">
                        <Input
                            type="email"
                            placeholder="colleague@company.com"
                            value={inviteEmail}
                            onChange={(e) => setInviteEmail(e.target.value)}
                            className="h-10"
                        />
                        <Button
                            type="button"
                            disabled={inviteBusy}
                            onClick={sendInvite}
                            className="shrink-0"
                        >
                            {inviteBusy ? (
                                <Loader2 className="h-4 w-4 animate-spin" />
                            ) : (
                                'Send invite'
                            )}
                        </Button>
                    </div>
                    {inviteResult?.error ? (
                        <p className="text-sm text-red-600 mt-3">{inviteResult.error}</p>
                    ) : null}
                    {inviteResult?.emailSent ? (
                        <p className="text-sm text-green-700 mt-3">
                            Invitation email sent to {inviteResult.inviteeEmail}.
                        </p>
                    ) : null}
                    {inviteResult?.emailError ? (
                        <p className="text-sm text-amber-800 mt-3">{inviteResult.emailError}</p>
                    ) : null}
                    {inviteResult?.url ? (
                        <div className="mt-4 space-y-2">
                            <p className="text-xs text-slate-600">
                                Invite link (copy if email did not arrive; expires in 7 days):
                            </p>
                            <Input readOnly value={inviteResult.url} className="text-xs h-9 font-mono" />
                        </div>
                    ) : null}
                </section>
                ) : null}

                {isAdmin ? (
                <section className="rounded-2xl border border-slate-200 bg-white p-6 shadow-sm">
                    <div className="flex items-center gap-2 text-slate-800 font-semibold mb-4">
                        <Users className="h-5 w-5 text-violet-600" />
                        Members
                    </div>
                    {membersLoading ? (
                        <div className="flex justify-center py-12 text-slate-400">
                            <Loader2 className="h-8 w-8 animate-spin" />
                        </div>
                    ) : membersError ? (
                        <p className="text-sm text-red-600">{membersError}</p>
                    ) : members.length === 0 ? (
                        <p className="text-sm text-slate-500">No members or pending invitations.</p>
                    ) : (
                        <div className="overflow-x-auto rounded-xl border border-slate-100">
                            <table className="w-full text-sm text-left">
                                <thead>
                                    <tr className="border-b border-slate-100 bg-slate-50/80">
                                        <th className="px-4 py-3 font-medium text-slate-600">Email</th>
                                        <th className="px-4 py-3 font-medium text-slate-600">Name</th>
                                        <th className="px-4 py-3 font-medium text-slate-600">Role</th>
                                        <th className="px-4 py-3 font-medium text-slate-600">Status</th>
                                        <th className="px-4 py-3 font-medium text-slate-600 w-28" />
                                    </tr>
                                </thead>
                                <tbody>
                                    {members.map((m) => {
                                        const rowKey =
                                            m.user_id != null ? `m-${m.user_id}` : `i-${m.invitation_id}`;
                                        const isSelf = m.user_id === me.user_id;
                                        const isInvited = m.status === 'invited';
                                        const busyMember = removeBusyKey === `member:${m.user_id}`;
                                        const busyInvite =
                                            m.invitation_id != null &&
                                            removeBusyKey === `invite:${m.invitation_id}`;
                                        return (
                                            <tr
                                                key={rowKey}
                                                className="border-b border-slate-50 last:border-0"
                                            >
                                                <td className="px-4 py-3 text-slate-900">
                                                    {m.email || '—'}
                                                </td>
                                                <td className="px-4 py-3 text-slate-700">
                                                    {m.name || '—'}
                                                </td>
                                                <td className="px-4 py-3">
                                                    <span
                                                        className={cn(
                                                            'inline-flex rounded-full px-2 py-0.5 text-xs font-medium',
                                                            m.role === 'admin'
                                                                ? 'bg-violet-100 text-violet-800'
                                                                : 'bg-slate-100 text-slate-700'
                                                        )}
                                                    >
                                                        {m.role}
                                                    </span>
                                                </td>
                                                <td className="px-4 py-3">
                                                    <span
                                                        className={cn(
                                                            'inline-flex rounded-full px-2 py-0.5 text-xs font-medium',
                                                            isInvited
                                                                ? 'bg-amber-50 text-amber-900 ring-1 ring-amber-200/80'
                                                                : 'bg-emerald-50 text-emerald-900 ring-1 ring-emerald-200/80'
                                                        )}
                                                    >
                                                        {isInvited ? 'Invited' : 'Active'}
                                                    </span>
                                                </td>
                                                <td className="px-4 py-3 text-right">
                                                    {isSelf ? (
                                                        <span className="text-xs text-slate-400">
                                                            You
                                                        </span>
                                                    ) : isInvited ? (
                                                        <Button
                                                            type="button"
                                                            variant="ghost"
                                                            size="sm"
                                                            className="h-8 text-red-600 hover:text-red-700 hover:bg-red-50"
                                                            disabled={busyInvite}
                                                            onClick={() => revokeInvitation(m.invitation_id)}
                                                            title="Cancel invitation"
                                                        >
                                                            {busyInvite ? (
                                                                <Loader2 className="h-4 w-4 animate-spin" />
                                                            ) : (
                                                                <Trash2 className="h-4 w-4" />
                                                            )}
                                                        </Button>
                                                    ) : (
                                                        <Button
                                                            type="button"
                                                            variant="ghost"
                                                            size="sm"
                                                            className="h-8 text-red-600 hover:text-red-700 hover:bg-red-50"
                                                            disabled={busyMember}
                                                            onClick={() => removeMember(m.user_id)}
                                                            title="Remove from workspace"
                                                        >
                                                            {busyMember ? (
                                                                <Loader2 className="h-4 w-4 animate-spin" />
                                                            ) : (
                                                                <Trash2 className="h-4 w-4" />
                                                            )}
                                                        </Button>
                                                    )}
                                                </td>
                                            </tr>
                                        );
                                    })}
                                </tbody>
                            </table>
                        </div>
                    )}
                </section>
                ) : null}

                <LinkedInConnectSettings />
                <ConnectMailboxSettings />

                <section className="rounded-2xl border border-slate-200 bg-white p-6 shadow-sm">
                    <div className="flex items-center gap-2 text-slate-800 font-semibold mb-2">
                        <Sparkles className="h-5 w-5 text-violet-600" />
                        Email / AI generator
                    </div>
                    <p className="text-sm text-slate-600 mb-4">
                        Import an Apollo CSV, choose products, edit prompts, and generate email sequences in
                        a guided flow. Opens full width here so you can focus on the tool.
                    </p>
                    <Button type="button" onClick={() => setSettingsPanel('email_generator')}>
                        Open Email / AI generator
                    </Button>
                </section>

                <section className="rounded-2xl border border-slate-200 bg-white p-6 shadow-sm">
                    <div className="flex items-center gap-2 text-slate-800 font-semibold mb-4">
                        <Link2 className="h-5 w-5 text-violet-600" />
                        Smartlead webhook
                    </div>
                    <p className="text-xs text-slate-500 mb-4">
                        Paste this URL in Smartlead so reply events are stored for this workspace. The link
                        includes <span className="font-mono text-slate-700">tenant_id</span> for the active
                        workspace.
                    </p>
                    <div className="flex flex-wrap items-center gap-2 mb-6">
                        <code className="text-xs bg-slate-100 px-2 py-1.5 rounded break-all flex-1 min-w-[12rem]">
                            {webhookUrl}
                        </code>
                        <Button
                            type="button"
                            variant="outline"
                            size="sm"
                            className="shrink-0 gap-1"
                            onClick={() => webhookUrl && navigator.clipboard.writeText(webhookUrl)}
                        >
                            <ClipboardCopy className="h-3.5 w-3.5" />
                            Copy
                        </Button>
                    </div>
                    {multiWorkspace ? (
                        <div className="pt-4 border-t border-slate-100">
                            <p className="text-xs font-medium text-slate-600 mb-2">Switch workspace</p>
                            <p className="text-xs text-slate-500 mb-2">
                                The webhook URL updates when you change workspace (different{' '}
                                <span className="font-mono">tenant_id</span>).
                            </p>
                            <Select
                                value={String(me.current_tenant_id ?? '')}
                                onValueChange={switchTenant}
                            >
                                <SelectTrigger className="h-10 max-w-md border-slate-200 text-sm">
                                    <SelectValue placeholder="Choose workspace" />
                                </SelectTrigger>
                                <SelectContent>
                                    {tenants.map((tn) => (
                                        <SelectItem key={tn.id} value={String(tn.id)}>
                                            {tn.name}
                                            {tn.role === 'admin' ? ' · admin' : ''}
                                        </SelectItem>
                                    ))}
                                </SelectContent>
                            </Select>
                        </div>
                    ) : null}
                </section>
            </div>
        </AppShell>
    );
}