import http from 'http'
import stream from 'stream'

/**
 * Router
 */

class Branch {
  constructor() {
    this.children = new Map()
    this.paramName = null
    this.fullparamName = null
    this.handler = null
    this.middlewares = []
  }
}

export const ErrorCodes = {
  ERR_CONNECTION_ABORTED: 'ERR_CON_ABORTED'
}

// Taken from https://github.com/nfp-projects/koa-lite/blob/master/lib/statuses.js
const statuses = {
  100: 'Continue', 101: 'Switching Protocols', 102: 'Processing', 103: 'Early Hints',
  200: 'OK', 201: 'Created', 202: 'Accepted', 203: 'Non-Authoritative Information', 204: 'No Content', 205: 'Reset Content', 206: 'Partial Content', 207: 'Multi-Status', 208: 'Already Reported', 226: 'IM Used',
  300: 'Multiple Choices', 301: 'Moved Permanently', 302: 'Found', 303: 'See Other', 304: 'Not Modified', 305: 'Use Proxy', 306: '(Unused)', 307: 'Temporary Redirect', 308: 'Permanent Redirect',
  400: 'Bad Request', 401: 'Unauthorized', 402: 'Payment Required', 403: 'Forbidden', 404: 'Not Found', 405: 'Method Not Allowed', 406: 'Not Acceptable', 407: 'Proxy Authentication Required', 408: 'Request Timeout', 409: 'Conflict', 410: 'Gone', 411: 'Length Required', 412: 'Precondition Failed', 413: 'Payload Too Large', 414: 'URI Too Long', 415: 'Unsupported Media Type', 416: 'Range Not Satisfiable', 417: 'Expectation Failed', 418: 'I\'m a teapot', 421: 'Misdirected Request', 422: 'Unprocessable Entity', 423: 'Locked', 424: 'Failed Dependency', 425: 'Too Early', 426: 'Upgrade Required', 428: 'Precondition Required', 429: 'Too Many Requests', 431: 'Request Header Fields Too Large', 451: 'Unavailable For Legal Reasons',
  500: 'Internal Server Error', 501: 'Not Implemented', 502: 'Bad Gateway', 503: 'Service Unavailable', 504: 'Gateway Timeout', 505: 'HTTP Version Not Supported', 506: 'Variant Also Negotiates', 507: 'Insufficient Storage', 508: 'Loop Detected', 509: 'Bandwidth Limit Exceeded', 510: 'Not Extended', 511: 'Network Authentication Required',
  redirect: {
    300: true,
    301: true,
    302: true,
    303: true,
    305: true,
    307: true,
    308: true
  },
  empty: {
    204: true,
    205: true,
    304: true
  }
}
const __paramMapName = '__param'
const __fullParamMapName = '__fullparam'

function assertIsHandler(handler, name) {
  if (typeof(handler) !== 'function') {
    throw new Error(`${name} was called with a handler that was not a function`)
  }
}

export class FlaskaRouter {
  constructor() {
    this.root = new Branch()
  }

  addRoute(route, orgMiddlewares, orgHandler) {
    if (route[0] !== '/')
      throw new Error(`route "${route}" must start with forward slash`)
  
    let middlewares = orgMiddlewares
    let handler = orgHandler
    if (!orgHandler) {
      handler = orgMiddlewares
      middlewares = []
    }
    if (middlewares && typeof(middlewares) === 'function') {
      middlewares = [middlewares]
    }
    assertIsHandler(handler, 'addRoute()')
  
    let start = 1
    let end = 1
    let name = ''
    let param = ''
    let isParam = false
    let isFullParam = false
    let branch = this.root
  
    if (route.indexOf(':') < 0) {
      let name = route
      if (name.length > 1 && name[name.length - 1] === '/') {
        name = name.slice(0, -1)
      }
      let child = new Branch()
      branch.children.set(name, child)
      child.handler = handler
      child.middlewares = middlewares
    }
  
    for (let i = 1; i <= route.length; i++) {
      if ((i === route.length || route[i] === '/') && end > start) {
        if (branch.fullparamName) {
          throw new Error(`route "${route}" conflicts with a sub-branch that has a full param child`)
        }
        let child
        name = route.substring(start, end)
        if (isFullParam) {
          param = name
          name = __fullParamMapName
        } else if (isParam) {
          param = name
          name = __paramMapName
        }
        if (branch.children.has(name)) {
          child = branch.children.get(name)
        }
        else if (isParam && !isFullParam && branch.children.has(__fullParamMapName)) {
          throw new Error(`route "${route}" conflicts with a sub-branch that has a full param child`)
        }
        else if (isFullParam && branch.children.has(__paramMapName)) {
          throw new Error(`route "${route}" conflicts with a sub-branch that has a partial param child`)
        }
        else {
          child = new Branch()
          branch.children.set(name, child)
        }
        branch = child
        end = i
        start = i
        if (isParam) {
          if (branch.paramName && branch.paramName !== param) {
            throw new Error(`route "${route}" conflicts with pre-existing param name of ${branch.paramName} instead of ${param}`)
          }
          if (isFullParam) {
            branch.fullparamName = param
          } else {
            branch.paramName = param
          }
          isParam = false
        }
      } else if (route[i] === '/' && end === start) {
        throw new Error(`route "${route}" has missing path name inbetween slashes`)
      }
      if (i === route.length) {
        branch.handler = handler
        branch.middlewares = middlewares
        continue
      }
      if (route[i] === ':') {
        if (isParam) {
          isFullParam = true
        }
        isParam = true
        end = start = i + 1
      }
      else if (route[i] === '/') {
        end = start = i + 1
      }
      else {
        end++
      }
    }
  }

  match(orgUrl) {
    let url = orgUrl
    if (url.length > 1 && url[url.length - 1] === '/') {
      url = url.slice(0, -1)
    }
    let branch = this.root
    let start = 1
    let end = 1
    let output
    let name
    let char
    let params = {}
    if (output = branch.children.get(url)) {
      return {
        handler: output.handler,
        middlewares: output.middlewares,
        params: params,
      }
    }
    for (let i = 1; i <= url.length; i++) {
      char = url[i]
      if ((i === url.length || char === '/') && end > start) {
        name = url.slice(start, end)
        if (output = branch.children.get(name)) {
          branch = output
        }
        else if (output = branch.children.get(__paramMapName)) {
          branch = output
          params[branch.paramName] = name
        }
        else if (output = branch.children.get(__fullParamMapName)) {
          params[output.fullparamName] = url.slice(start)
          return {
            handler: output.handler,
            middlewares: output.middlewares,
            params: params,
          }
        } else {
          if (output = this.root.children.get(__fullParamMapName)) {
            params = {
              [output.fullparamName]: url.slice(1)
            }
            return {
              handler: output.handler,
              middlewares: output.middlewares,
              params: params,
            }
          }
          return null
        }
        i++
        end = start = i
        char = url[i]
      }
      // Check branch.handler. This can happen if route /::path is added
      // and request is '/' it will attempt to match root which will fail
      if (i >= url.length && branch.handler) {
        return {
          handler: branch.handler,
          middlewares: branch.middlewares,
          params: params,
        }
      }
      if (char === '/') {
        end = start = i + 1
      } else {
        end++
      }
    }
    if (output = this.root.children.get(__fullParamMapName)) {
      params = {
        [output.fullparamName]: url.slice(1)
      }
      return {
        handler: output.handler,
        middlewares: output.middlewares,
        params: params,
      }
    }
    return null
  }
}

/**
 * Flaska
 */
export class Flaska {
  constructor(opts, orgHttp = http, orgStream = stream) {
    this._before = []
    this._beforeCompiled = null
    this._beforeAsync = []
    this._beforeAsyncCompiled = null
    this._after = []
    this._afterCompiled = null
    this._afterAsync = []
    this._afterAsyncCompiled = null
    this._on404 = function(ctx) {
      ctx.status = 404
      ctx.body = {
        status: 404,
        message: statuses[404],
      }
    }
    this._backuperror = this._onerror = function(err, ctx) {
      ctx.log.error(err)
      ctx.status = 500
      ctx.body = {
        status: 500,
        message: statuses[500],
      }
    }
    this._onreqerror = function(err, ctx) {
      ctx.log.error(err)
      ctx.res.statusCode = ctx.statusCode = 400
      ctx.res.end()
      ctx.finished = true
    }
    this._onreserror = function(err, ctx) {
      ctx.log.error(err)
    }

    let options = opts || {}

    this.log = options.log || console
    this.http = orgHttp
    this.stream = orgStream
    this.server = null
    this.routers = {
      'GET': new FlaskaRouter(),
      'POST': new FlaskaRouter(),
      'PUT': new FlaskaRouter(),
      'DELETE': new FlaskaRouter(),
      'OPTIONS': new FlaskaRouter(),
      'PATCH': new FlaskaRouter(),
    }
    this.get = this.routers.GET.addRoute.bind(this.routers.GET)
    this.post = this.routers.POST.addRoute.bind(this.routers.POST)
    this.put = this.routers.PUT.addRoute.bind(this.routers.PUT)
    this.delete = this.routers.DELETE.addRoute.bind(this.routers.DELETE)
    this.options = this.routers.OPTIONS.addRoute.bind(this.routers.OPTIONS)
    this.patch = this.routers.PATCH.addRoute.bind(this.routers.PATCH)
  }

  _assertIsHandler(handler, name) {
    if (typeof(handler) !== 'function') {
      throw new Error(`${name} was called with a handler that was not a function`)
    }
  }

  devMode() {
    this._backuperror = this._onerror = function(err, ctx) {
      ctx.log.error(err)
      ctx.status = 500
      ctx.body = {
        status: 500,
        message: `${statuses[500]}: ${err.message}`,
        stack: err.stack || '',
      }
    }
  }

  on404(handler) {
    assertIsHandler(handler, 'on404()')
    this._on404 = handler
  }

  onerror(handler) {
    assertIsHandler(handler, 'onerror()')
    this._onerror = handler
  }

  onreqerror(handler) {
    assertIsHandler(handler, 'onreqerror()')
    this._onreqerror = handler
  }
  
  onreserror(handler) {
    assertIsHandler(handler, 'onreserror()')
    this._onreserror = handler
  }

  onerror(handler) {
    assertIsHandler(handler, 'onerror()')
    this._onerror = handler
  }

  before(handler) {
    assertIsHandler(handler, 'before()')
    this._before.push(handler)
  }

  beforeAsync(handler) {
    assertIsHandler(handler, 'beforeAsync()')
    this._beforeAsync.push(handler)
  }
  
  after(handler) {
    assertIsHandler(handler, 'after()')
    this._after.push(handler)
  }

  afterAsync(handler) {
    assertIsHandler(handler, 'afterAsync()')
    this._afterAsync.push(handler)
  }
  
  requestStart(req, res) {
    let url = req.url
    let search = ''
    let hasSearch = url.indexOf('?')

    if (hasSearch > 0) {
      search = url.slice(hasSearch)
      url = url.slice(0, hasSearch)
    }

    let ctx = {
      log: this.log,
      req: req,
      res: res,
      method: req.method,
      url: url,
      search: search,
      state: {},
      status: 200,
      body: null,
      type: null,
      length: null,
    }

    req.on('error', (err) => {
      this._onreqerror(err, ctx)
    })
    res.on('error', (err) => {
      this._onreserror(err, ctx)
    })

    req.on('aborted', function() {
      ctx.aborted = true
    })
    req.on('close', () => {
      this.requestEnded()
    })

    try {
      this._beforeCompiled(ctx)
      if (this._beforeAsyncCompiled) {
        return this._beforeAsyncCompiled(ctx)
          .then(() => {
            this.requestStartInternal(ctx)
          }).catch(err => {
            this.requestEnd(err, ctx)
          })
      }
      this.requestStartInternal(ctx)
    }
    catch (err) {
      this.requestEnd(err, ctx)
    }
  }

  requestStartInternal(ctx) {
    let route = this.routers[ctx.method].match(ctx.url)
    ctx.params = route.params

    if (route.middlewares.length) {
      let middle = this.handleMiddleware(ctx, route.middlewares, 0)

      if (middle && middle.then) {
        return middle.then(() => {
          return route.handler(ctx)
        })
        .then(() => {
          this.requestEnd(null, ctx)
        }, err => {
          this.requestEnd(err, ctx)
        })
      }
    }
    let handler = route.handler(ctx)
    if (handler && handler.then) {
      return handler.then(() => {
        this.requestEnd(null, ctx)
      }, err => {
        this.requestEnd(err, ctx)
      })
    }
    this.requestEnd(null, ctx)
  }

  handleMiddleware(ctx, middles, index) {
    for (let i = index; i < middles.length; i++) {
      let res = middles[i](ctx)
      if (res && res.then) {
        return res.then(() => {
          return this.handleMiddleware(ctx, middles, i + 1)
        })
      }
    }
  }

  requestEnd(err, ctx) {
    if (err) {
      this._onerror(err, ctx)
      return ctx.res.end()
    }
    if (ctx.req.complete) {
      return
    }

    ctx.res.statusCode = ctx.status
    if (statuses.empty[ctx.status]) {
      return ctx.res.end()
    }

    let body = ctx.body
    let length = 0
    if (body && typeof(body.pipe) === 'function') {
      ctx.res.setHeader('Content-Type', ctx.type || 'application/octet-stream')
      return this.stream.pipeline(body, ctx.res, function() {})
    }
    if (typeof(body) === 'object') {
      body = JSON.stringify(body)
      length = Buffer.byteLength(body)
      ctx.res.setHeader('Content-Type', 'application/json; charset=utf-8')
    } else {
      body = body.toString()
      length = Buffer.byteLength(body)
      ctx.res.setHeader('Content-Type', ctx.type || 'text/plain; charset=utf-8')
    }
    ctx.res.setHeader('Content-Length', length)
    ctx.res.end(body)
  }

  requestEnded(ctx) {
    this._afterCompiled(ctx)
    if (this._afterAsyncCompiled) {
      return this._afterAsyncCompiled(ctx).then()
    }
  }

  compile() {
    let types = ['before', 'after']
    for (let i = 0; i < types.length; i++) {
      let type = types[i]
      let args = ''
      let body = ''
      for (let i = 0; i < this['_' + type].length; i++) {
        args += `a${i}, `
        body += `a${i}(ctx);`
      }
      args += 'ctx'

      let func = new Function(args, body)
      this[`_${type}Compiled`] = func.bind(this, ...this['_' + type])

      if (this[`_${type}Async`].length) {
        args = ''
        body = 'return Promise.all(['
        for (let i = 0; i < this[`_${type}Async`].length; i++) {
          args += `a${i}, `
          body += `a${i}(ctx),`
        }
        args += 'ctx'
        body += '])'
        func = new Function(args, body)
        this[`_${type}AsyncCompiled`] = func.bind(this, ...this[`_${type}Async`])
      }
    }
  }

  listen(port, cb) {
    if (typeof(port) !== 'number') {
      throw new Error('Flaska.listen() called with non-number in port')
    }
    this.compile()
    this.server = this.http.createServer(this.requestStart.bind(this))
    this.server.listen(port, cb)
  }
}