import {applyPatches, parsePatch} from '@sanity/diff-match-patch'

type fn = (oldVal: any, newVal: any) => any
const OPERATIONS: Record<string, fn> = {
  replace(_currentValue: any, nextValue: any) {
    return nextValue
  },
  set(_currentValue: any, nextValue: any) {
    return nextValue
  },
  setIfMissing(currentValue: undefined, nextValue: any) {
    return currentValue === undefined ? nextValue : currentValue
  },
  unset(_currentValue: any, _nextValue: any) {
    return undefined
  },
  diffMatchPatch(currentValue: string, nextValue: string): string {
    const [result] = applyPatches(parsePatch(nextValue), currentValue, {
      allowExceedingIndices: true,
    })
    return result
  },
}

const SUPPORTED_PATCH_TYPES = Object.keys(OPERATIONS)

export default function apply(
  value: string,
  patch: {type: string; path: any[]; value: any},
): string {
  if (!SUPPORTED_PATCH_TYPES.includes(patch.type)) {
    throw new Error(
      `Received patch of unsupported type: "${JSON.stringify(
        patch.type,
      )}" for string. This is most likely a bug.`,
    )
  }

  if (patch.path.length > 0) {
    throw new Error(
      `Cannot apply deep operations on string values. Received patch with type "${
        patch.type
      }" and path "${patch.path.join('.')} that targeted the value "${JSON.stringify(value)}"`,
    )
  }
  const func = OPERATIONS[patch.type]
  if (func) {
    return func(value, patch.value)
  }
  throw new Error('Unknown patch type')
}