import type { TransformCallback } from 'postcss'

export const removeUnusedKeyframes: TransformCallback = (root) => {
  // Store all keyframes and their usage status
  const keyframes = new Map<string, boolean>()

  root.walk((node) => {
    if (node.type === 'atrule' && node.name === 'keyframes') {
      // Record the keyframe and mark it as unused
      keyframes.set(node.params, false)
    } else if (node.type === 'decl') {
      const decl = node
      const animationName = decl.prop === 'animation' ? decl.value.split(' ')[0] : decl.value

      if ((decl.prop === 'animation' || decl.prop === 'animation-name') && keyframes.has(animationName)) {
        // Mark the keyframe as used
        keyframes.set(animationName, true)
      }
    }
  })

  // Remove unused keyframes
  root.walkAtRules('keyframes', (rule) => {
    if (keyframes.get(rule.params) === false) {
      rule.remove()
    }
  })
}