| One frontend where there were three, and a core that is not Clojure 438b247 nandi yesterday | 1 | ## The C ABI, and nothing else. |
| 2 | ## |
| 3 | ## Every exported symbol is here so there is one file to read when asking what |
| 4 | ## the Dart side can call. The logic lives under `frq/` in ordinary Nim with |
| 5 | ## ordinary Nim types, which is what lets the tests test the rules rather than |
| 6 | ## the marshalling. |
| 7 | ## |
| 8 | ## Two conventions, both of which the bindings in `flutter/src/frq/core/` |
| 9 | ## wrap so no call site has to remember them: |
| 10 | ## |
| 11 | ## * Every returned string is the **caller's** to free, with `frq_free`. Nim's |
| 12 | ## allocator is not Dart's, so a `free()` on this side of the boundary is |
| 13 | ## undefined behaviour rather than a leak you can live with. |
| 14 | ## * `frq_init` runs once before anything else. Nim's runtime needs setting up |
| 15 | ## and `--app:lib` does not do it for you on every platform. |
| 16 | ## |
| 17 | ## Answers that are not a single string come back as JSON. A struct would mean |
| 18 | ## both sides agreeing on a memory layout, and a field added later would be a |
| 19 | ## version skew that segfaults rather than one that fails; JSON costs a parse |
| 20 | ## per call, which is nothing against the network round trip that produced the |
| 21 | ## line being parsed. |
| 22 | |
| 23 | import std/json |
| Nim owns the screen, Dart owns the pixels 43a02c2 nandi yesterday | 24 | import frq/[ircparse, ui, state] |
| 25 | import frq/screens/connect as connectScreen |
| One frontend where there were three, and a core that is not Clojure 438b247 nandi yesterday | 26 | |
| 27 | proc NimMain() {.importc.} |
| 28 | |
| 29 | var initialised = false |
| 30 | |
| 31 | proc frq_init*() {.exportc, dynlib.} = |
| 32 | ## Set Nim's runtime up. Idempotent, because a binding that guesses wrong |
| 33 | ## about whether it has been called should be harmless rather than fatal. |
| 34 | if not initialised: |
| 35 | NimMain() |
| 36 | initialised = true |
| 37 | |
| 38 | proc dup(s: string): cstring = |
| 39 | ## A copy of `s` that outlives this call, for the caller to `frq_free`. |
| 40 | ## `allocShared0` and not `alloc0`: the Dart side may free it from a |
| 41 | ## different thread than the one that made it. |
| 42 | let n = s.len |
| 43 | let p = cast[cstring](allocShared0(n + 1)) |
| 44 | if n > 0: |
| 45 | copyMem(p, unsafeAddr s[0], n) |
| 46 | p |
| 47 | |
| 48 | proc frq_free*(p: cstring) {.exportc, dynlib.} = |
| 49 | ## Free what one of the functions below returned. Null is fine. |
| 50 | if p != nil: |
| 51 | deallocShared(p) |
| 52 | |
| 53 | proc frq_version*(): cstring {.exportc, dynlib.} = |
| 54 | ## Static storage, deliberately: this one is NOT freed, and is the only |
| 55 | ## exception to the rule above. It exists so a binding can check at load |
| 56 | ## time that the library it found is the one it was built against. |
| 57 | "0.1.0" |
| 58 | |
| 59 | # ----------------------------------------------------------------- irc/parse |
| 60 | |
| 61 | proc frq_irc_parse_line*(line: cstring): cstring {.exportc, dynlib.} = |
| 62 | ## An IRC line as JSON: `{raw, tags, account, prefix, command, params}`. |
| 63 | ## |
| 64 | ## `tags`, `account` and `prefix` are JSON null where the line carried none, |
| 65 | ## which is the distinction `frq.irc.parse` draws with nil and every caller |
| 66 | ## of it depends on — a PRIVMSG from a server with no prefix is not the same |
| 67 | ## line as one from a nick. |
| 68 | if line == nil: return dup("null") |
| 69 | let p = parseLine($line) |
| 70 | var o = newJObject() |
| 71 | o["raw"] = %p.raw |
| 72 | o["tags"] = if p.hasTags: %p.tags else: newJNull() |
| 73 | o["account"] = if p.hasAccount: %p.account else: newJNull() |
| 74 | o["prefix"] = if p.hasPrefix: %p.prefix else: newJNull() |
| 75 | o["command"] = %p.command |
| 76 | o["params"] = %p.params |
| 77 | dup($o) |
| 78 | |
| 79 | proc frq_irc_tag_value*(tags, key: cstring): cstring {.exportc, dynlib.} = |
| 80 | ## One tag's value, unescaped — or **null** where the tag is absent or |
| 81 | ## empty, which IRCv3 says are the same thing. Null and not "" on purpose: |
| 82 | ## see `tagValue`. |
| 83 | if tags == nil or key == nil: return nil |
| 84 | let (v, ok) = tagValue($tags, $key) |
| 85 | if ok: dup(v) else: nil |
| 86 | |
| 87 | proc frq_irc_unescape_tag*(v: cstring): cstring {.exportc, dynlib.} = |
| 88 | if v == nil: return nil |
| 89 | dup(unescapeTag($v)) |
| 90 | |
| 91 | proc frq_irc_escape_tag_value*(v: cstring): cstring {.exportc, dynlib.} = |
| 92 | if v == nil: return dup("") |
| 93 | dup(escapeTagValue($v)) |
| 94 | |
| 95 | proc frq_irc_nick_of*(prefix: cstring): cstring {.exportc, dynlib.} = |
| 96 | if prefix == nil: return nil |
| 97 | dup(nickOf($prefix)) |
| Nim owns the screen, Dart owns the pixels 43a02c2 nandi yesterday | 98 | |
| 99 | # ------------------------------------------------------------------- the UI |
| 100 | # |
| 101 | # The spike's real claim: Nim owns the state and the screen, Dart owns the |
| 102 | # pixels, and the only things crossing are a tree going out and an event id |
| 103 | # coming back. See `frq/ui.nim`. |
| 104 | |
| 105 | proc frq_ui_render*(): cstring {.exportc, dynlib.} = |
| 106 | ## The current screen as a widget tree, in JSON. Pure: calling it twice with |
| 107 | ## no dispatch between gives the same answer, which is what lets the |
| 108 | ## renderer rebuild whenever Flutter asks rather than when Nim says so. |
| 109 | dup($connectScreen.connectScreen(app).toJson) |
| 110 | |
| 111 | proc frq_ui_dispatch*(event: cstring): cstring {.exportc, dynlib.} = |
| 112 | ## Apply an event and answer with the tree it produced. |
| 113 | ## |
| 114 | ## One call rather than dispatch-then-render, and not to save a crossing: |
| 115 | ## it makes the pair atomic. Two calls leave a window in which Dart could |
| 116 | ## render a state nothing asked for, which is the sort of thing that shows |
| 117 | ## up once a week and never in a test. |
| 118 | ## |
| 119 | ## A malformed event is ignored rather than fatal — it arrives from a tree |
| 120 | ## the renderer may have been holding for a frame, which is a normal race. |
| 121 | if event != nil: |
| 122 | try: |
| 123 | dispatch(parseJson($event)) |
| 124 | except JsonParsingError: |
| 125 | discard |
| 126 | dup($connectScreen.connectScreen(app).toJson) |
| 127 | |
| 128 | proc frq_ui_reset*() {.exportc, dynlib.} = |
| 129 | ## Back to a fresh state. For tests, and for a renderer that wants a known |
| 130 | ## starting point rather than whatever the last run left. |
| 131 | app = initState() |