'use strict'
exports.__esModule = true

const pkgDir = require('pkg-dir')

const fs = require('fs')
const path = require('path')

const hashObject = require('./hash').hashObject
    , ModuleCache = require('./ModuleCache').default

const CASE_SENSITIVE_FS = !fs.existsSync(path.join(__dirname, 'reSOLVE.js'))
exports.CASE_SENSITIVE_FS = CASE_SENSITIVE_FS

const fileExistsCache = new ModuleCache()

function tryRequire(target) {
  let resolved
  try {
    // Check if the target exists
    resolved = require.resolve(target)
  } catch(e) {
    // If the target does not exist then just return undefined
    return undefined
  }

  // If the target exists then return the loaded module
  return require(resolved)
}

// http://stackoverflow.com/a/27382838
exports.fileExistsWithCaseSync = function fileExistsWithCaseSync(filepath, cacheSettings) {
  // don't care if the FS is case-sensitive
  if (CASE_SENSITIVE_FS) return true

  // null means it resolved to a builtin
  if (filepath === null) return true
  if (filepath.toLowerCase() === process.cwd().toLowerCase()) return true
  const parsedPath = path.parse(filepath)
      , dir = parsedPath.dir

  let result = fileExistsCache.get(filepath, cacheSettings)
  if (result != null) return result

  // base case
  if (dir === '' || parsedPath.root === filepath) {
    result = true
  } else {
    const filenames = fs.readdirSync(dir)
    if (filenames.indexOf(parsedPath.base) === -1) {
      result = false
    } else {
      result = fileExistsWithCaseSync(dir, cacheSettings)
    }
  }
  fileExistsCache.set(filepath, result)
  return result
}

function relative(modulePath, sourceFile, settings) {
  return fullResolve(modulePath, sourceFile, settings).path
}

function fullResolve(modulePath, sourceFile, settings) {
  // check if this is a bonus core module
  const coreSet = new Set(settings['import/core-modules'])
  if (coreSet.has(modulePath)) return { found: true, path: null }

  const sourceDir = path.dirname(sourceFile)
      , cacheKey = sourceDir + hashObject(settings).digest('hex') + modulePath

  const cacheSettings = ModuleCache.getSettings(settings)

  const cachedPath = fileExistsCache.get(cacheKey, cacheSettings)
  if (cachedPath !== undefined) return { found: true, path: cachedPath }

  function cache(resolvedPath) {
    fileExistsCache.set(cacheKey, resolvedPath)
  }

  function withResolver(resolver, config) {

    function v1() {
      try {
        const resolved = resolver.resolveImport(modulePath, sourceFile, config)
        if (resolved === undefined) return { found: false }
        return { found: true, path: resolved }
      } catch (err) {
        return { found: false }
      }
    }

    function v2() {
      return resolver.resolve(modulePath, sourceFile, config)
    }

    switch (resolver.interfaceVersion) {
      case 2:
        return v2()

      default:
      case 1:
        return v1()
    }
  }

  const configResolvers = (settings['import/resolver']
    || { 'node': settings['import/resolve'] }) // backward compatibility

  const resolvers = resolverReducer(configResolvers, new Map())

  for (let pair of resolvers) {
    let name = pair[0]
      , config = pair[1]
    const resolver = requireResolver(name, sourceFile)
        , resolved = withResolver(resolver, config)

    if (!resolved.found) continue

    // else, counts
    cache(resolved.path)
    return resolved
  }

  // failed
  // cache(undefined)
  return { found: false }
}
exports.relative = relative

function resolverReducer(resolvers, map) {
  if (resolvers instanceof Array) {
    resolvers.forEach(r => resolverReducer(r, map))
    return map
  }

  if (typeof resolvers === 'string') {
    map.set(resolvers, null)
    return map
  }

  if (typeof resolvers === 'object') {
    for (let key in resolvers) {
      map.set(key, resolvers[key])
    }
    return map
  }

  throw new Error('invalid resolver config')
}

function getBaseDir(sourceFile) {
  return pkgDir.sync(sourceFile) || process.cwd()
}
function requireResolver(name, sourceFile) {
  // Try to resolve package with conventional name
  let resolver = tryRequire(`eslint-import-resolver-${name}`) ||
    tryRequire(name) ||
    tryRequire(path.resolve(getBaseDir(sourceFile), name))

  if (!resolver) {
    throw new Error(`unable to load resolver "${name}".`)
  }
  if (!isResolverValid(resolver)) {
    throw new Error(`${name} with invalid interface loaded as resolver`)
  }

  return resolver
}

function isResolverValid(resolver) {
  if (resolver.interfaceVersion === 2) {
    return resolver.resolve && typeof resolver.resolve === 'function'
  } else {
    return resolver.resolveImport && typeof resolver.resolveImport === 'function'
  }
}

const erroredContexts = new Set()

/**
 * Given
 * @param  {string} p - module path
 * @param  {object} context - ESLint context
 * @return {string} - the full module filesystem path;
 *                    null if package is core;
 *                    undefined if not found
 */
function resolve(p, context) {
  try {
    return relative( p
                   , context.getFilename()
                   , context.settings
                   )
  } catch (err) {
    if (!erroredContexts.has(context)) {
      context.report({
        message: `Resolve error: ${err.message}`,
        loc: { line: 1, column: 0 },
      })
      erroredContexts.add(context)
    }
  }
}
resolve.relative = relative
exports.default = resolve
