hono/deno_dist/helper/html/index.ts

import { escapeToBuffer, stringBufferToString } from '../../utils/html.ts'
import type {
  StringBuffer,
  HtmlEscaped,
  HtmlEscapedString,
  HtmlEscapedCallback,
} from '../../utils/html.ts'

export const raw = (value: unknown, callbacks?: HtmlEscapedCallback[]): HtmlEscapedString => {
  const escapedString = new String(value) as HtmlEscapedString
  escapedString.isEscaped = true
  escapedString.callbacks = callbacks

  return escapedString
}

export const html = (
  strings: TemplateStringsArray,
  ...values: unknown[]
): HtmlEscapedString | Promise<HtmlEscapedString> => {
  const buffer: StringBuffer = ['']

  for (let i = 0, len = strings.length - 1; i < len; i++) {
    buffer[0] += strings[i]

    const children =
      values[i] instanceof Array ? (values[i] as Array<unknown>).flat(Infinity) : [values[i]]
    for (let i = 0, len = children.length; i < len; i++) {
      // eslint-disable-next-line @typescript-eslint/no-explicit-any
      const child = children[i] as any
      if (typeof child === 'string') {
        escapeToBuffer(child, buffer)
      } else if (typeof child === 'boolean' || child === null || child === undefined) {
        continue
      } else if (
        (typeof child === 'object' && (child as HtmlEscaped).isEscaped) ||
        typeof child === 'number'
      ) {
        const tmp = child.toString()
        if (tmp instanceof Promise) {
          buffer.unshift('', tmp)
        } else {
          buffer[0] += tmp
        }
      } else {
        escapeToBuffer(child.toString(), buffer)
      }
    }
  }
  buffer[0] += strings[strings.length - 1]

  return buffer.length === 1 ? raw(buffer[0]) : stringBufferToString(buffer)
}