Implement pretty issue rendering

lib/gh/issue.ml

@@ -1,9 +1,15 @@
 module Json = Yojson.Basic.Util
 
+type label = {
+  name : string;
+  color : string;
+}
+
 type t = {
   number : int;
   title : string;
   author : string;
+  labels : label list;
 }
 
 let mk_issues_query ~owner ~repo =
@@ -18,28 +24,57 @@ query {
           author {
             login
           }
+          labels(first: 100) {
+            nodes {
+              name
+              color
+            }
+          }
         }
     }
   }
 }
 |}
     owner repo
 
+(* Parse single label from JSON:
+
+{
+  "name": "good first issue",
+  "color": "7057ff"
+}
+*)
+let parse_label json =
+  let name = Json.(json |> member "name" |> to_string) in
+  let color = Json.(json |> member "color" |> to_string) in
+  { name; color }
+
 (* Parse single issue from JSON:
 
 {
   "number": 18,
   "title": "GitHub TUI: Release Tracker for v1.0",
   "author": {
     "login": "chshersh"
+  },
+  "labels": {
+    "nodes": [
+      {
+        "name": "good first issue",
+        "color": "7057ff"
+      }
+    ]
   }
 }
 *)
 let parse_issue json =
-  let number = Json.(member "number" json |> to_int) in
-  let title = Json.(member "title" json |> to_string) in
-  let author = Json.(member "author" json |> member "login" |> to_string) in
-  { number; title; author }
+  let number = Json.(json |> member "number" |> to_int) in
+  let title = Json.(json |> member "title" |> to_string) in
+  let author = Json.(json |> member "author" |> member "login" |> to_string) in
+  let labels =
+    Json.(json |> member "labels" |> member "nodes" |> convert_each parse_label)
+  in
+  { number; title; author; labels }
 
 (* Parse a list of 't' from the following JSON:
 

lib/gh/issue.mli

@@ -1,7 +1,13 @@
+type label = {
+  name : string;
+  color : string;
+}
+
 type t = {
   number : int;
   title : string;
   author : string;
+  labels : label list;
 }
 
 (** Query all open issues *)

lib/pretty/color.ml

@@ -0,0 +1,27 @@
+type t = RGB of int * int * int
+
+let to_255 str =
+  match int_of_string_opt ("0x" ^ str) with
+  | None -> 0
+  | Some c -> c
+
+let rgb r g b = RGB (to_255 r, to_255 g, to_255 b)
+
+let rgb str =
+  match String.to_seq str |> List.of_seq |> List.map (String.make 1) with
+  | [ "#"; r1; r2; g1; g2; b1; b2 ] -> rgb (r1 ^ r2) (g1 ^ g2) (b1 ^ b2)
+  | [ "#"; r1; g1; b1 ] -> rgb r1 g1 b1
+  | _ -> RGB (0, 0, 0)
+
+let of_hex str =
+  if String.starts_with ~prefix:"#" str then rgb str else rgb ("#" ^ str)
+
+(* Calculate the luminance of colour. When applied to background colour, this
+   function could be used to detect the corresponding foreground colour. *)
+let luminance (RGB (r, g, b)) =
+  let scale x = float_of_int x /. 255.0 in
+  let r, g, b = (scale r, scale g, scale b) in
+  (0.2126 *. r) +. (0.7152 *. g) +. (0.0722 *. b)
+
+let foreground color = if luminance color < 0.3 then `Light else `Dark
+let to_escape_seq (RGB (r, g, b)) = Format.sprintf "2;%d;%d;%d" r g b

lib/pretty/color.mli

@@ -0,0 +1,16 @@
+(** This module provides utilities to work with colors. *)
+
+(** An RGB colour code *)
+type t
+
+(** Returns RGB colour from a hex string like "7057f" or "#fbca04".
+
+    Returns black colour by default if there's a parsing error. *)
+val of_hex : string -> t
+
+(** This function calculates the luminance of colour and suggests a foreground
+    colour. *)
+val foreground : t -> [ `Light | `Dark ]
+
+(** Convert code to escape sequence. *)
+val to_escape_seq : t -> string

lib/pretty/pretty.ml

@@ -1,3 +1,4 @@
+module Color = Color
 module Doc = Doc
 module Layout = Layout
 

lib/pretty/pretty.mli

@@ -10,6 +10,9 @@ module Doc = Doc
     {!Layout.t} is the output of {!Doc.render} with all the sizes calculated. *)
 module Layout = Layout
 
+(** Color-related functions. *)
+module Color = Color
+
 (** Render a document into the final string
 
     All notes from {!Doc.render} apply. *)

lib/pretty/style.ml

@@ -1,5 +1,8 @@
 type t = ANSITerminal.style list
 
+let fg_black = ANSITerminal.[ Foreground Black ]
+let fg_white = ANSITerminal.[ Foreground White ]
+let green = ANSITerminal.[ green ]
 let repo = ANSITerminal.[ Bold; blue ]
 let selected = ANSITerminal.[ Bold; green ]
 let directory = ANSITerminal.[ Bold; magenta ]

lib/tui/view.ml

@@ -21,17 +21,44 @@ let code_section (code_tab : Model.code_tab) =
   let fs_doc = Widget.file_view code_tab.fs in
   Pretty.Doc.vertical [ current_path_doc; fs_doc ]
 
+let issue_char = "\u{f41b}"
+
+let apply_background_color ~color text =
+  let module Color = Pretty.Color in
+  let color = Color.of_hex color in
+  let foreground_suggestion = Color.foreground color in
+  let color_code = Pretty.Color.to_escape_seq color in
+  let text = Printf.sprintf "\027[48;%sm %s \027[0m" color_code text in
+  (text, foreground_suggestion)
+
 let issues_section (issues_tab : Model.issues_tab) =
+  let open Pretty.Layout in
+  let fmt_title (issue : Gh.Issue.t) =
+    horizontal
+      [
+        fmt Style.green issue_char;
+        str "  ";
+        fmt Style.secondary (Printf.sprintf "#%d " issue.number);
+        str issue.title;
+        str " by ";
+        fmt Style.bold (Printf.sprintf "@%s" issue.author);
+      ]
+  in
+  let fmt_labels labels =
+    let fmt_label (label : Gh.Issue.label) =
+      let label, foreground =
+        apply_background_color ~color:label.color label.name
+      in
+      let label = label ^ " " in
+      match foreground with
+      | `Light -> fmt Style.fg_white label
+      | `Dark -> fmt Style.fg_black label
+    in
+    labels |> List.map fmt_label |> fun labels ->
+    horizontal (str "   " :: labels)
+  in
   let fmt_issue (issue : Gh.Issue.t) =
-    Pretty.Layout.(
-      horizontal
-        [
-          str " ";
-          fmt Style.secondary (Printf.sprintf "#%d " issue.number);
-          str issue.title;
-          str " by ";
-          fmt Style.bold (Printf.sprintf "@%s" issue.author);
-        ])
+    vertical [ fmt_title issue; fmt_labels issue.labels ]
   in
   issues_tab.issues
   |> Lazy.force