import React, { useState } from 'react';

export interface SpacingValue {
  top: string;
  right: string;
  bottom: string;
  left: string;
}

interface SpacingInputProps {
  label: string;
  value: SpacingValue;
  onChange: (value: SpacingValue) => void;
}

const UNITS = ['px', 'em', '%'] as const;

const labelStyle: React.CSSProperties = {
  fontSize: 11, fontWeight: 600, color: '#a1a1aa', display: 'block', marginBottom: 6,
  textTransform: 'uppercase', letterSpacing: '0.3px',
};

const inputStyle: React.CSSProperties = {
  width: '100%', padding: '4px 6px', background: '#27272a', color: '#e4e4e7',
  border: '1px solid #3f3f46', borderRadius: 4, fontSize: 11, textAlign: 'center',
};

const sideLabel: React.CSSProperties = {
  fontSize: 9, color: '#71717a', textAlign: 'center', marginTop: 2, textTransform: 'uppercase',
  letterSpacing: '0.5px',
};

function parseValue(val: string): { num: string; unit: string } {
  const match = val.match(/^(-?\d*\.?\d+)\s*(px|em|%|rem)?$/);
  if (match) return { num: match[1], unit: match[2] || 'px' };
  return { num: val.replace(/[^0-9.-]/g, '') || '0', unit: 'px' };
}

export const SpacingInput: React.FC<SpacingInputProps> = ({ label, value, onChange }) => {
  const [linked, setLinked] = useState(false);
  const [unit, setUnit] = useState<string>(() => parseValue(value.top).unit || 'px');

  const handleSideChange = (side: keyof SpacingValue, raw: string) => {
    const numericPart = raw.replace(/[^0-9.-]/g, '');
    const newVal = numericPart ? `${numericPart}${unit}` : '0';

    if (linked) {
      onChange({ top: newVal, right: newVal, bottom: newVal, left: newVal });
    } else {
      onChange({ ...value, [side]: newVal });
    }
  };

  const handleUnitChange = (newUnit: string) => {
    setUnit(newUnit);
    // Re-apply current numeric values with new unit
    const updated: SpacingValue = { top: '', right: '', bottom: '', left: '' };
    for (const side of ['top', 'right', 'bottom', 'left'] as const) {
      const { num } = parseValue(value[side]);
      updated[side] = num && num !== '0' ? `${num}${newUnit}` : '0';
    }
    onChange(updated);
  };

  const sides: { key: keyof SpacingValue; label: string }[] = [
    { key: 'top', label: 'T' },
    { key: 'right', label: 'R' },
    { key: 'bottom', label: 'B' },
    { key: 'left', label: 'L' },
  ];

  return (
    <div style={{ marginBottom: 12 }}>
      <div style={{ display: 'flex', alignItems: 'center', justifyContent: 'space-between', marginBottom: 6 }}>
        <label style={{ ...labelStyle, marginBottom: 0 }}>{label}</label>
        <div style={{ display: 'flex', alignItems: 'center', gap: 6 }}>
          {/* Unit selector */}
          <div style={{ display: 'flex', gap: 2 }}>
            {UNITS.map((u) => (
              <button
                key={u}
                onClick={() => handleUnitChange(u)}
                style={{
                  padding: '1px 5px', fontSize: 9, borderRadius: 3, cursor: 'pointer',
                  border: '1px solid #3f3f46',
                  background: unit === u ? '#3b82f6' : '#27272a',
                  color: unit === u ? '#fff' : '#71717a',
                }}
              >{u}</button>
            ))}
          </div>
          {/* Link toggle */}
          <button
            onClick={() => setLinked(!linked)}
            title={linked ? 'Unlink sides' : 'Link all sides'}
            style={{
              padding: '2px 6px', fontSize: 11, borderRadius: 3, cursor: 'pointer',
              border: '1px solid #3f3f46',
              background: linked ? '#3b82f6' : '#27272a',
              color: linked ? '#fff' : '#71717a',
            }}
          >
            <i className={`fa ${linked ? 'fa-link' : 'fa-unlink'}`} style={{ fontSize: 9 }} />
          </button>
        </div>
      </div>
      <div style={{ display: 'grid', gridTemplateColumns: '1fr 1fr 1fr 1fr', gap: 4 }}>
        {sides.map((s) => (
          <div key={s.key}>
            <input
              type="text"
              value={parseValue(value[s.key]).num}
              onChange={(e) => handleSideChange(s.key, e.target.value)}
              style={inputStyle}
            />
            <div style={sideLabel}>{s.label}</div>
          </div>
        ))}
      </div>
    </div>
  );
};

/** Parse a CSS shorthand like "10px 20px 10px 20px" or "10px" into SpacingValue */
export function parseSpacingShorthand(val: string | undefined): SpacingValue {
  if (!val) return { top: '0', right: '0', bottom: '0', left: '0' };
  const parts = val.trim().split(/\s+/);
  if (parts.length === 1) return { top: parts[0], right: parts[0], bottom: parts[0], left: parts[0] };
  if (parts.length === 2) return { top: parts[0], right: parts[1], bottom: parts[0], left: parts[1] };
  if (parts.length === 3) return { top: parts[0], right: parts[1], bottom: parts[2], left: parts[1] };
  return { top: parts[0], right: parts[1], bottom: parts[2], left: parts[3] };
}

/** Convert SpacingValue back to CSS shorthand */
export function spacingToShorthand(val: SpacingValue): string {
  const { top, right, bottom, left } = val;
  if (top === right && right === bottom && bottom === left) return top || '0';
  if (top === bottom && right === left) return `${top} ${right}`;
  if (right === left) return `${top} ${right} ${bottom}`;
  return `${top} ${right} ${bottom} ${left}`;
}