const PREFIX_GENERIC = '--'
const PREFIX_STANDARD_NOTES = '--sn-stylekit'
const PREFIX_STANDARD_NOTES_BURN = '--sn-'

function camelCaseToDashed(camel: string) {
  return camel.replace(/[A-Z]/g, m => '-' + m.toLowerCase())
}

export function objectToCss(object: any) {
  let result = ''
  for (const key of Object.keys(object)) {
    const dashed = `sn-${camelCaseToDashed(key).toLowerCase()}`
    const line = `--${dashed}: ${object[key]};\n`
    result += line
  }
  return `
    :root {
      ${result}
    }
  `
}

export default class CSSParser {
  /**
   * @param css: CSS file contents in string format
   */
  static cssToObject(css: string) {
    const object: Record<string, string> = {}
    const lines = css.split('\n')

    for (let line of lines) {
      line = line.trim()
      if (line.startsWith(PREFIX_GENERIC)) {
        // Remove initial '--'
        if (line.startsWith(PREFIX_STANDARD_NOTES)) {
          line = line.slice(PREFIX_STANDARD_NOTES_BURN.length, line.length)
        } else {
          // Not all vars start with --sn-stylekit. e.g --background-color
          line = line.slice(PREFIX_GENERIC.length, line.length)
        }
        const parts = line.split(':')
        let key = parts[0].trim()
        let value = parts[1].trim()

        key = this.hyphenatedStringToCamelCase(key)
        value = value.replace(';', '').trim()

        object[key] = value
      }
    }

    this.resolveVariablesThatReferenceOtherVariables(object)

    return object
  }

  static resolveVariablesThatReferenceOtherVariables(object: Record<string, any>, round = 0) {
    for (const key of Object.keys(object)) {
      const value = object[key]
      const stripValue = 'var('
      if (typeof value === 'string' && value.startsWith(stripValue)) {
        const from = stripValue.length
        const to = value.indexOf(')')
        let varName = value.slice(from, to)
        if (varName.startsWith(PREFIX_STANDARD_NOTES)) {
          varName = varName.slice(PREFIX_STANDARD_NOTES_BURN.length, varName.length)
        } else {
          // Not all vars start with --sn-stylekit. e.g --background-color
          varName = varName.slice(PREFIX_GENERIC.length, varName.length)
        }
        varName = this.hyphenatedStringToCamelCase(varName)
        object[key] = object[varName]
      }
    }

    // Two rounds are required. The first will replace all right hand side variables with
    // the left hand counterparts. In the first round, variables on rhs mentioned before
    // its value has been gotten to in the loop will be missed. The second round takes care of this
    // and makes sure that all values will resolve.
    if (round === 0) {
      this.resolveVariablesThatReferenceOtherVariables(object, ++round)
    }
  }

  static hyphenatedStringToCamelCase(string: string) {
    const comps = string.split('-')
    let result = ''
    for (let i = 0; i < comps.length; i++) {
      const part = comps[i]
      if (i === 0) {
        result += part
      } else {
        result += this.capitalizeFirstLetter(part)
      }
    }

    return result
  }

  static capitalizeFirstLetter(string: string) {
    return string.charAt(0).toUpperCase() + string.slice(1)
  }
}