streamer VS spaghetti ninjas

Streamer library, which suggests opinionated stream definition / pattern and utilizes core library, that makes asynchronously recursive, pure function <3 possible without spaghetti code ninjas!

Transcript

1. streamer VS spaghetti ninjas
3. gozala
4. gozala ირაკლი გოზალიშვილი
5. gozala @mozilla.com ირაკლი გოზალიშვილი
6. gozala @mozilla.com ირაკლი გოზალიშვილი Function <3
7. I <3 non-blocking nature of JS The way we do it makes me :(
8. black box input output
9. function blackbox(a, b) { var c = assemble(a) return combine(b, c) }
10. input output
11. function spaghetti(a, b, callback) { assemble(a, function(error, c) { if (error) callback(error) else combine(b, c, callback) }) }
12. spaghetti box input callback
13. input callback
15. function listTree(path, callback) { fs.readdir(path, function(error, entries) { if (error) return callback(error) function onStateChange(e, paths) { if (e) return callback(error = e) result = result.concat(paths) if (--waiting === 0) callback(null, result) } function onStat(path, e, stat) { if (error) return null // error already reported if (e) return callback(error = e) if (!stat.isDirectory()) onStateChange(null, [ path ]) else listTree(path, onStateChange) } var waiting = entries.length, result = [ path ] if (!waiting) return callback(null, result) entries.forEach(function(entry) { entry = join(path, entry) fs.stat(entry, onStat.bind(null, entry)) }) })
16. What can we do about this ?
17. black box input output
18. data type for eventual value
19. streamer
20. sequence of elements made available over time
21. We <3 Function
22. function stream() {}
23. function stream(next) {}
24. function stream(next) { next(1) next(2) next(3) }
25. stream(console.log)
26. stream(console.log)
27. function print(source) { source(function onEach(element) { console.log(element) }) } print(stream) // 1 // 2 // 3
28. function numbers(min, max) { var d = max - min return function stream(next) { setInterval(function generate() { next(min + Math.round(Math.random() * d)) }, 20) } } print(numbers(0, 100))
29. streams may be ∞
30. function stream(next, stop) { next(1) next(2) next(3) stop() }
31. what about errors ?
32. function stream(next, stop) { stop(Error('Boom!')) }
33. function print(stream) { console.log('>>>') // start stream(function onElement(element) { console.log(element) // yeild }, function onStop(error) { if (!error) return console.log('<<<') console.log('!!!') console.error(error) }) }
34. print(stream) // >>> // 1 // 2 // 3 // <<<
35. now slides after beer
36. function list() { // Capture arguments as an array. var array array = Array.prototype.slice.call(arguments) return function stream(next, stop) { array.forEach(function(element) { next(element) }) stop() } }
37. print(list(1, 2, 3)) // >>> // 1 // 2 // 3 // <<<
38. function listTree(path, callback) { fs.readdir(path, function(error, entries) { if (error) return callback(error) function onStateChange(e, paths) { if (e) return callback(error = e) result = result.concat(paths) if (--waiting === 0) callback(null, result) } function onStat(path, e, stat) { if (error) return null // error already reported if (e) return callback(error = e) if (!stat.isDirectory()) onStateChange(null, [ path ]) else listTree(path, onStateChange) } var waiting = entries.length, result = [ path ] if (!waiting) return callback(null, result) entries.forEach(function(entry) { entry = join(path, entry) fs.stat(entry, onStat.bind(null, entry)) }) })
39. var fs = require("fs") var path = require("path") function ls(base) { return function stream(next, stop) { fs.readdir(base, function(error, entries) { var entry // stop on error with error if (error) return stop(error) // Otherwise we yield each entry. while ((entry = entries.shift())) next(path.join(base, entry)) stop() }) } }
40. print(ls('./')) // >>> // ./.gitignore // ./History.md // ./package.json // ./readme.js // ./Readme.md // ./streamer.js // ./tests // <<<
41. function stat(path) { return function stream(next, stop) { fs.stat(path, function(error, stats) { // if error, stop stream with error. if (error) return stop(error) // save path to find stat’s owner stats.path = path // We yield `stats` and stop the stream. next(stats) stop() }) } }
42. print(stat('./')) // >>> // { dev: 234881026, // ino: 19933437, // mode: 16877, // nlink: 17, // uid: 502, // gid: 20, // rdev: 0, // size: 578, // blksize: 4096, // blocks: 0, // atime: Thu, 09 Jun 2011 10:51:25 GMT, // mtime: Thu, 09 Jun 2011 12:48:32 GMT, // ctime: Thu, 09 Jun 2011 12:48:32 GMT, // path: './' }
43. function map(lambda, source) { return function stream(next, stop) { source(function onElement(element) { next(lambda(element)) }, stop) } }
44. print(map(function(x) { return x * 2 }, list(1, 2, 3))) // >>> // 2 // 4 // 6 // <<<
45. function filter(lambda, source) { return function stream(next, stop) { source(function onElement(element) { if (lambda(element)) next(element) }, stop) } }
46. print(filter(function(x) { return x % 2 }, list(1, 2, 3, 4))) // >>> // 1 // 3 // <<<
47. function dirs(paths) { var stats = map(stat, paths) var dirStats = filter(function(stat) { return stat.isDirectory() }, stats) return map(function(stat) { return stat.path }, dirStats) }
48. function merge(source) { return function stream(next, stop) { var open = 1 function onStop(error) { if (!open) return false if (error) open = 0 else open -- if (!open) stop(error) } source(function onStream(stream) { open ++ stream(function(value) { if (open) next(value) }, onStop) }, onStop) }
49. print(merge(list(list(1, 2), list('a', 'b')))) // >>> // 1 // 2 // a // b // <<<
50. function dirs(paths) { var stats = merge(map(paths, stat)) var dirStats = filter(function(stat) { return stat.isDirectory() }, stats) return map(function(stat) { return stat.path }, dirStats) }
51. print(dirs(ls(process.cwd()))) // >>> // /Users/gozala/streamer/.git // /Users/gozala/streamer/node_modules // ... // <<<
52. function lstree(path) { var paths = ls(path) var nested = merge(map(lstree, dirs(paths))) return merge(list(paths, nested)) }
53. function listTree(path, callback) { fs.readdir(path, function(error, entries) { if (error) return callback(error) function onStateChange(e, paths) { if (e) return callback(error = e) result = result.concat(paths) if (--waiting === 0) callback(null, result) } function onStat(path, e, stat) { if (error) return null // error already reported if (e) return callback(error = e) if (!stat.isDirectory()) onStateChange(null, [ path ]) else listTree(path, onStateChange) } var waiting = entries.length, result = [ path ] if (!waiting) return callback(null, result) entries.forEach(function(entry) { entry = join(path, entry) fs.stat(entry, onStat.bind(null, entry)) }) })
54. function dirs(paths) { var stats = merge(map(paths, stat)) var dirStats = filter(function($) { return $.isDirectory() }, stats) return map(function(stat) { return stat.path }, dirStats) } function lstree(path) { var paths = ls(path) var nested = merge(map(lstree, dirs(paths))) return merge(list(paths, nested)) }
55. function blackbox(a, b) { var c = assemble(a) return combine(b, c) }
56. function blackbox(a, b) { var c = assemble(a) return combine(b, c) } function assemble(a) { return function stream(next, stop) { fs.readFile(a, function(e, content) { e ? stop(e) : next(context) }) } } function combine(b, c) { return map(function($) { return $ + b }, c) }
57. Questions ?
58. What is it good for ?
59. var http = require('http-streamer/request') var response = http.put({ url: 'http://myhost.com/upload', body: fs.read(path) // async! })
60. var http = require('http-streamer/server') var fs = require('fs-streamer') var streamer = require('streamer') var server = http.server(function(request) { return { status: 200, head: { 'ContentType': 'text/plain' }, body: streamer.append(fs.read(header), request.body, fs.read(footer)) } }, 8080)
61. var http = require('http-streamer/server') var streamer = require('streamer') function domEvents(target, type, capture) { return function stream(next, stop) { target.addEventListener(type, function onEvent(event) { if (false === next(event)) target.removeEventListener(type, onEvent, !!capture) }, !!capture) } } var keys = domEvents(document, 'keypress') var codes = streamer.map(function($) { return url + '?q=' + $.keyCode }, keys) var data = streamer.merge(streamer.map(http.get, codes)) print(data)