/**
 * This webpack resolver is largely based on TypeScript's "paths" handling
 * The TypeScript license can be found here:
 * https://github.com/microsoft/TypeScript/blob/214df64e287804577afa1fea0184c18c40f7d1ca/LICENSE.txt
 */
import { ResolvePlugin } from 'webpack'
import { join } from 'path'

export interface Pattern {
  prefix: string
  suffix: string
}

const asterisk = 0x2a

export function hasZeroOrOneAsteriskCharacter(str: string): boolean {
  let seenAsterisk = false
  for (let i = 0; i < str.length; i++) {
    if (str.charCodeAt(i) === asterisk) {
      if (!seenAsterisk) {
        seenAsterisk = true
      } else {
        // have already seen asterisk
        return false
      }
    }
  }
  return true
}

export function tryParsePattern(pattern: string): Pattern | undefined {
  // This should be verified outside of here and a proper error thrown.
  const indexOfStar = pattern.indexOf('*')
  return indexOfStar === -1
    ? undefined
    : {
        prefix: pattern.substr(0, indexOfStar),
        suffix: pattern.substr(indexOfStar + 1),
      }
}

function isPatternMatch({ prefix, suffix }: Pattern, candidate: string) {
  return (
    candidate.length >= prefix.length + suffix.length &&
    candidate.startsWith(prefix) &&
    candidate.endsWith(suffix)
  )
}

/** Return the object corresponding to the best pattern to match `candidate`. */
export function findBestPatternMatch<T>(
  values: readonly T[],
  getPattern: (value: T) => Pattern,
  candidate: string
): T | undefined {
  let matchedValue: T | undefined
  // use length of prefix as betterness criteria
  let longestMatchPrefixLength = -1

  for (const v of values) {
    const pattern = getPattern(v)
    if (
      isPatternMatch(pattern, candidate) &&
      pattern.prefix.length > longestMatchPrefixLength
    ) {
      longestMatchPrefixLength = pattern.prefix.length
      matchedValue = v
    }
  }

  return matchedValue
}

/**
 * patternStrings contains both pattern strings (containing "*") and regular strings.
 * Return an exact match if possible, or a pattern match, or undefined.
 * (These are verified by verifyCompilerOptions to have 0 or 1 "*" characters.)
 */
export function matchPatternOrExact(
  patternStrings: readonly string[],
  candidate: string
): string | Pattern | undefined {
  const patterns: Pattern[] = []
  for (const patternString of patternStrings) {
    if (!hasZeroOrOneAsteriskCharacter(patternString)) continue
    const pattern = tryParsePattern(patternString)
    if (pattern) {
      patterns.push(pattern)
    } else if (patternString === candidate) {
      // pattern was matched as is - no need to search further
      return patternString
    }
  }

  return findBestPatternMatch(patterns, _ => _, candidate)
}

/**
 * Tests whether a value is string
 */
export function isString(text: unknown): text is string {
  return typeof text === 'string'
}

/**
 * Given that candidate matches pattern, returns the text matching the '*'.
 * E.g.: matchedText(tryParsePattern("foo*baz"), "foobarbaz") === "bar"
 */
export function matchedText(pattern: Pattern, candidate: string): string {
  return candidate.substring(
    pattern.prefix.length,
    candidate.length - pattern.suffix.length
  )
}

export function patternText({ prefix, suffix }: Pattern): string {
  return `${prefix}*${suffix}`
}

const NODE_MODULES_REGEX = /node_modules/

type Paths = { [match: string]: string[] }

/**
 * Handles tsconfig.json or jsconfig.js "paths" option for webpack
 * Largely based on how the TypeScript compiler handles it:
 * https://github.com/microsoft/TypeScript/blob/1a9c8197fffe3dace5f8dca6633d450a88cba66d/src/compiler/moduleNameResolver.ts#L1362
 */
export class JsConfigPathsPlugin implements ResolvePlugin {
  paths: Paths
  resolvedBaseUrl: string
  constructor(paths: Paths, resolvedBaseUrl: string) {
    this.paths = paths

    this.resolvedBaseUrl = resolvedBaseUrl
  }
  apply(resolver: any) {
    const paths = this.paths
    const pathsKeys = Object.keys(paths)

    // If no aliases are added bail out
    if (pathsKeys.length === 0) {
      return
    }

    const baseDirectory = this.resolvedBaseUrl
    const target = resolver.ensureHook('resolve')
    resolver
      .getHook('described-resolve')
      .tapPromise(
        'JsConfigPathsPlugin',
        async (request: any, resolveContext: any) => {
          // Exclude node_modules from paths support (speeds up resolving)
          if (request.path.match(NODE_MODULES_REGEX)) {
            return
          }

          const moduleName = request.request

          // If the module name does not match any of the patterns in `paths` we hand off resolving to webpack
          const matchedPattern = matchPatternOrExact(pathsKeys, moduleName)
          if (!matchedPattern) {
            return
          }

          const matchedStar = isString(matchedPattern)
            ? undefined
            : matchedText(matchedPattern, moduleName)
          const matchedPatternText = isString(matchedPattern)
            ? matchedPattern
            : patternText(matchedPattern)

          let triedPaths = []

          for (const subst of paths[matchedPatternText]) {
            const path = matchedStar ? subst.replace('*', matchedStar) : subst

            // Ensure .d.ts is not matched
            if (path.endsWith('.d.ts')) {
              continue
            }

            const candidate = join(baseDirectory, path)
            const [err, result] = await new Promise((resolve, reject) => {
              const obj = Object.assign({}, request, {
                request: candidate,
              })
              resolver.doResolve(
                target,
                obj,
                `Aliased with tsconfig.json or jsconfig.json ${matchedPatternText} to ${candidate}`,
                resolveContext,
                (err: any, result: any | undefined) => {
                  resolve([err, result])
                }
              )
            })

            // There's multiple paths values possible, so we first have to iterate them all first before throwing an error
            if (err || result === undefined) {
              triedPaths.push(candidate)
              continue
            }

            return result
          }

          throw new Error(`
      Request "${moduleName}" matched tsconfig.json or jsconfig.json "paths" pattern ${matchedPatternText} but could not be resolved.
      Tried paths: ${triedPaths.join(' ')}
      `)
        }
      )
  }
}