Initial commit of the bones of an unused-open-removing Agda tool

AgdaUnusedOpens/AgdaFile.fs

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+namespace AgdaUnusedOpens
+
+open AgdaUnusedOpens.Internals
+open System.IO
+open System.Text.RegularExpressions
+open AgdaUnusedOpens.Types
+
+[<RequireQualifiedAccess>]
+module Path =
+    let fold<'s> (f : 's -> string -> 's) (initial : 's) (p : Path) : 's =
+        p.Tail
+        |> List.fold f (f initial p.Head)
+
+    let toString (p : Path) : string =
+        match p.Tail with
+        | [] ->
+            p.Head
+        | _ ->
+            sprintf "%s.%s" p.Head (String.concat "." p.Tail)
+
+    let combine (agdaRoot : DirectoryInfo) (p : Path) : FileInfo =
+        p
+        |> fold (fun soFar next -> Path.Combine (soFar, next)) agdaRoot.FullName
+        |> FileInfo
+
+    let rename (newModule : string) (p : Path) =
+        match p.Tail with
+        | [] -> { Head = newModule ; Tail = [] }
+        | t -> { Head = p.Head ; Tail = t |> List.rev |> List.tail |> (fun i -> newModule :: i) |> List.rev }
+
+    let make (p : string list) =
+        match p with
+        | [] -> failwith "You fool"
+        | x :: xs ->
+            {
+                Head = x
+                Tail = xs
+            }
+
+/// An in-memory representation of an Agda file.
+type AgdaFile =
+    internal
+        {
+            Path : Path
+            Contents : string list
+            /// Line number of the line which contains the module statement
+            ModuleLine : int
+        }
+
+[<RequireQualifiedAccess>]
+module AgdaFile =
+    let make (lines : string list) : AgdaFile =
+        let moduleLineNo, moduleLine =
+            lines
+            |> List.indexed
+            |> List.filter (fun (_, line) -> line.TrimStart().StartsWith "module ")
+            |> List.exactlyOne
+        let pathRegex = Regex ".*module ([^ ]+) .*where"
+        let path =
+            (pathRegex.Match moduleLine).Groups.[1].Value.Split('.')
+            |> Array.toList
+            |> Path.make
+
+        {
+            Path = path
+            Contents = lines
+            ModuleLine = moduleLineNo
+        }
+
+    let flush (agdaRoot : DirectoryInfo) (f : AgdaFile) : unit =
+        let location = Path.combine agdaRoot f.Path
+        File.WriteAllLines (location.FullName, f.Contents)
+
+    let rename (newName : string) (f : AgdaFile) : AgdaFile =
+        let newPath = Path.rename newName f.Path
+        {
+            Path = newPath
+            Contents =
+                let currentLine = f.Contents.[f.ModuleLine]
+                let newLine =
+                    let i = currentLine.IndexOf "module " + String.length "module "
+                    sprintf "%s%s%s" (currentLine.Substring(0, i)) (Path.toString newPath) (currentLine.Substring(currentLine.IndexOf(' ', i)))
+                f.Contents
+                |> List.replaceAt f.ModuleLine newLine
+            ModuleLine = f.ModuleLine
+        }
+