import type { FC } from 'react';
import { useMemo } from 'react';

import { FontAwesomeIcon } from '@fortawesome/react-fontawesome';
import { faCircleCheck, faTriangleExclamation, faCircleExclamation } from '@fortawesome/pro-duotone-svg-icons';
import { cx } from '@/utils/cx';
import type { Lead } from '@/types/entities';

const CheckCircle: FC<{ className?: string }> = ({ className }) => <FontAwesomeIcon icon={faCircleCheck} className={className} />;
const AlertTriangle: FC<{ className?: string }> = ({ className }) => <FontAwesomeIcon icon={faTriangleExclamation} className={className} />;
const AlertCircle: FC<{ className?: string }> = ({ className }) => <FontAwesomeIcon icon={faCircleExclamation} className={className} />;

interface SlaMetricsProps {
    leads: Lead[];
}

const SLA_TARGET_HOURS = 2;

export const SlaMetrics = ({ leads }: SlaMetricsProps) => {
    const metrics = useMemo(() => {
        const responseTimes: number[] = [];
        let withinSla = 0;
        let total = leads.length;

        for (const lead of leads) {
            if (lead.createdAt && lead.firstContactedAt) {
                const created = new Date(lead.createdAt).getTime();
                const contacted = new Date(lead.firstContactedAt).getTime();
                const diffHours = (contacted - created) / (1000 * 60 * 60);
                responseTimes.push(diffHours);

                if (diffHours <= SLA_TARGET_HOURS) {
                    withinSla++;
                }
            }
            // Leads without firstContactedAt are counted as outside SLA
        }

        const avgHours =
            responseTimes.length > 0
                ? responseTimes.reduce((sum, h) => sum + h, 0) / responseTimes.length
                : 0;

        const slaPercent = total > 0 ? (withinSla / total) * 100 : 0;

        return { avgHours, withinSla, total, slaPercent };
    }, [leads]);

    const getTargetStatus = (): { icon: FC<{ className?: string }>; label: string; colorClass: string } => {
        const diff = metrics.avgHours - SLA_TARGET_HOURS;

        if (diff <= 0) {
            return {
                icon: CheckCircle,
                label: 'Below target',
                colorClass: 'text-success-primary',
            };
        }

        if (diff <= 0.5) {
            return {
                icon: AlertTriangle,
                label: 'Near target',
                colorClass: 'text-warning-primary',
            };
        }

        return {
            icon: AlertCircle,
            label: 'Above target',
            colorClass: 'text-error-primary',
        };
    };

    const status = getTargetStatus();
    const StatusIcon = status.icon;

    return (
        <div className="rounded-2xl border border-secondary bg-primary p-5">
            <h3 className="text-sm font-bold text-primary">Response SLA</h3>

            <div className="mt-4 flex items-end gap-3">
                <span className="text-display-sm font-bold text-primary">
                    {metrics.avgHours.toFixed(1)}h
                </span>
                <div className="mb-1 flex items-center gap-1">
                    <span className="text-xs text-tertiary">Target: {SLA_TARGET_HOURS}h</span>
                    <StatusIcon className={cx('size-4', status.colorClass)} />
                </div>
            </div>

            <span className={cx('mt-1 block text-xs font-medium', status.colorClass)}>
                {status.label}
            </span>

            <div className="mt-4">
                <div className="flex items-center justify-between text-xs text-tertiary">
                    <span>SLA Compliance</span>
                    <span className="font-medium text-primary">{Math.round(metrics.slaPercent)}%</span>
                </div>
                <div className="mt-1.5 h-2 w-full overflow-hidden rounded-full bg-tertiary">
                    <div
                        className={cx(
                            'h-full rounded-full transition-all',
                            metrics.slaPercent >= 80
                                ? 'bg-success-500'
                                : metrics.slaPercent >= 60
                                  ? 'bg-warning-500'
                                  : 'bg-error-500',
                        )}
                        style={{ width: `${metrics.slaPercent}%` }}
                    />
                </div>
                <span className="mt-1.5 block text-xs text-tertiary">
                    {metrics.withinSla} of {metrics.total} leads within SLA ({Math.round(metrics.slaPercent)}%)
                </span>
            </div>
        </div>
    );
};