extract TileMap and Pos modules

Makefile

@@ -3,6 +3,7 @@ default: frontend/frontend.js dist-newstyle/build/x86_64-linux/ghc-9.6.5/souples
 dist-newstyle/build/x86_64-linux/ghc-9.6.5/souplesse-0.1.0.0/x/souplesse/build/souplesse/souplesse: app/*.hs lib/*.hs
 	cabal build
 
-frontend/frontend.js: frontend/src/Main.elm frontend/src/Lib.elm frontend/src/Point.elm
+FRONTEND=Main.elm Lib.elm Point.elm Pos.elm TileMap.elm
+frontend/frontend.js: $(patsubst %,frontend/src/%,$(FRONTEND))
 	elm-test frontend/tests/
 	elm make --output=$@ $<

frontend/src/Main.elm

@@ -11,7 +11,8 @@ import Lib exposing(..)
 import List.Extra exposing(find)
 import Json.Decode as D
 import Http
-import Point exposing(Point, Pos ,decoder)
+import Point exposing (Point, decoder)
+import Pos exposing (Pos)
 import Svg exposing (Svg, svg, rect, g, polyline, line)
 import Svg.Attributes as S exposing
     ( viewBox
@@ -22,6 +23,7 @@ import Svg.Attributes as S exposing
     , fill
     , stroke, strokeWidth, strokeOpacity)
 import Time
+import TileMap exposing (..) -- (tiles, FineZoomLevel, toZoomCoord, toCoord)
 import Url.Parser exposing (Parser, (<?>), int, map, s, string)
 import Url.Parser.Query as Query
 import Url exposing (Url)
@@ -47,73 +49,6 @@ main =
 
 -- MATHS
 
--- Coordinates in a Mercator projection
-type alias Coord = { x: Float, y: Float }
-
--- zoom level
-type alias ZoomLevel = Int
-type FineZoomLevel = FineZoomLevel Int
-
-zoomStep = 8
-
-toZoom : FineZoomLevel -> ZoomLevel
-toZoom (FineZoomLevel f) = f // zoomStep
-
-
-incZoom : FineZoomLevel -> Int -> FineZoomLevel
-incZoom (FineZoomLevel z) delta =
-    FineZoomLevel (clamp 0 (20 * zoomStep) (z + delta))
-
-type alias TileNumber = { x: Int, y: Int }
-
--- project lat/long to co-ordinates based on pseudocode at
--- https://wiki.openstreetmap.org/wiki/Slippy_map_tilenames#Zoom_levels
-
-sec x = 1 / (cos x)
-
-toCoord : Pos -> Coord
-toCoord pos =
-    let
-        lat_rad = pos.lat * pi / 180
-        x = (pos.lon + 180) / 360
-        y = (1 - (logBase e ((tan lat_rad) + (sec lat_rad))) / pi) / 2
-    in
-        Coord x y
-
-pixelsToCoord z (x,y) =
-    let x_float = toFloat x / toFloat ( 2 ^ (z + 8))
-        y_float = toFloat y / toFloat ( 2 ^ (z + 8))
-    in Coord x_float y_float
-
-reflect : Coord -> Coord
-reflect c = Coord -c.x -c.y
-
--- translate : a -> a -> a
-translate base offset =
-    { base | x = (base.x + offset.x), y = (base.y + offset.y) }
-
-translatePixels : Coord -> ZoomLevel -> (Int, Int) -> Coord
-translatePixels old z (x, y) = translate old (pixelsToCoord z (x, y))
-
-
-tileCovering : Coord -> ZoomLevel -> TileNumber
-tileCovering c z =
-    TileNumber (truncate (toFloat (2 ^ z) * c.x)) (truncate (toFloat (2 ^ z) * c.y))
-
-pixelFromCoord : Coord -> ZoomLevel -> (Int, Int)
-pixelFromCoord c z =
-    let {x,y} = tileCovering c (z + 8)
-    in (x,y)
-
-boundingTiles : Coord -> ZoomLevel -> Int -> Int -> (TileNumber, TileNumber)
-boundingTiles centre z width height =
-    -- find the tiles needed to cover the area (`width` x `height`)
-    -- about the point at `centre`
-    let delta = pixelsToCoord z ((width // 2), (height // 2))
-        minCoord = translate centre (reflect delta)
-        maxCoord = translate centre delta
-    in ((tileCovering minCoord z),
-        (translate (tileCovering maxCoord z) (TileNumber 1 1)))
 
 -- MODEL
 
@@ -314,18 +249,6 @@ timeTick duration =
            Just n -> n
            Nothing -> width
 
-tileUrl : TileNumber -> ZoomLevel -> String
-tileUrl {x,y} z =
-    String.concat ["https://a.tile.openstreetmap.org",
-                       "/", String.fromInt z,
-                       "/", String.fromInt x,
-                       "/", String.fromInt y,
-                       ".png" ]
-
-tileImg zoom tilenumber = img [ width 256,
-                                height 256,
-                                src (tileUrl tilenumber zoom) ] []
-
 type alias Colour = String
 
 measureView : String -> Colour -> (Point -> Maybe Float) -> List Point -> Svg Msg
@@ -578,12 +501,6 @@ trackView leftedge topedge zoom points =
 
 px x = String.fromInt x ++ "px"
 
-tiles xs ys zoom =
-    List.map
-        (\ y -> div []
-             (List.map (\ x -> tileImg zoom (TileNumber x y)) xs))
-        ys
-
 ifTrack : Model -> (List Point ->  Html msg) ->  Html msg
 ifTrack model content =
     case model.track of

frontend/src/Point.elm

@@ -1,12 +1,7 @@
-module Point exposing(Pos, Point, decoder, downsample, duration, subseq, startTime, centre)
+module Point exposing(Point, decoder, downsample, duration, subseq, startTime, centre)
 
 import Json.Decode as D
-
+import Pos exposing (Pos)
-type alias Pos =
-    { lat : Float
-    , lon : Float
-    , ele : Maybe Float
-    }
 
 
 type alias Point =

frontend/src/Pos.elm

@@ -0,0 +1,7 @@
+module Pos exposing (Pos)
+
+type alias Pos =
+    { lat : Float
+    , lon : Float
+    , ele : Maybe Float
+    }

frontend/src/TileMap.elm

@@ -0,0 +1,105 @@
+module TileMap exposing (tiles
+                        , FineZoomLevel(..)
+                        , ZoomLevel
+                        , Coord
+                        , toCoord
+                        , toZoom
+                        , translate
+                        , translatePixels
+                        , incZoom
+                        , boundingTiles
+                        , pixelsToCoord
+                        , pixelFromCoord
+                        , zoomStep)
+
+import Html exposing (img, div)
+import Html.Attributes as H exposing (src, style, width, height)
+
+import Pos exposing (Pos)
+
+type alias TileNumber = { x: Int, y: Int }
+
+-- Coordinates in a Mercator projection
+type alias Coord = { x: Float, y: Float }
+
+-- zoom level
+type alias ZoomLevel = Int
+type FineZoomLevel = FineZoomLevel Int
+
+zoomStep = 8
+
+toZoom : FineZoomLevel -> ZoomLevel
+toZoom (FineZoomLevel f) = f // zoomStep
+
+
+incZoom : FineZoomLevel -> Int -> FineZoomLevel
+incZoom (FineZoomLevel z) delta =
+    FineZoomLevel (clamp 0 (20 * zoomStep) (z + delta))
+
+
+-- project lat/long to co-ordinates based on pseudocode at
+-- https://wiki.openstreetmap.org/wiki/Slippy_map_tilenames#Zoom_levels
+
+sec x = 1 / (cos x)
+
+toCoord : Pos -> Coord
+toCoord pos =
+    let
+        lat_rad = pos.lat * pi / 180
+        x = (pos.lon + 180) / 360
+        y = (1 - (logBase e ((tan lat_rad) + (sec lat_rad))) / pi) / 2
+    in
+        Coord x y
+
+pixelsToCoord z (x,y) =
+    let x_float = toFloat x / toFloat ( 2 ^ (z + 8))
+        y_float = toFloat y / toFloat ( 2 ^ (z + 8))
+    in Coord x_float y_float
+
+reflect : Coord -> Coord
+reflect c = Coord -c.x -c.y
+
+-- translate : a -> a -> a
+translate base offset =
+    { base | x = (base.x + offset.x), y = (base.y + offset.y) }
+
+translatePixels : Coord -> ZoomLevel -> (Int, Int) -> Coord
+translatePixels old z (x, y) = translate old (pixelsToCoord z (x, y))
+
+
+tileCovering : Coord -> ZoomLevel -> TileNumber
+tileCovering c z =
+    TileNumber (truncate (toFloat (2 ^ z) * c.x)) (truncate (toFloat (2 ^ z) * c.y))
+
+pixelFromCoord : Coord -> ZoomLevel -> (Int, Int)
+pixelFromCoord c z =
+    let {x,y} = tileCovering c (z + 8)
+    in (x,y)
+
+boundingTiles : Coord -> ZoomLevel -> Int -> Int -> (TileNumber, TileNumber)
+boundingTiles centre z width height =
+    -- find the tiles needed to cover the area (`width` x `height`)
+    -- about the point at `centre`
+    let delta = pixelsToCoord z ((width // 2), (height // 2))
+        minCoord = translate centre (reflect delta)
+        maxCoord = translate centre delta
+    in ((tileCovering minCoord z),
+        (translate (tileCovering maxCoord z) (TileNumber 1 1)))
+
+tileUrl : TileNumber -> ZoomLevel -> String
+tileUrl {x,y} z =
+    String.concat ["https://a.tile.openstreetmap.org",
+                       "/", String.fromInt z,
+                       "/", String.fromInt x,
+                       "/", String.fromInt y,
+                       ".png" ]
+
+tileImg zoom tilenumber = img [ width 256,
+                                height 256,
+                                src (tileUrl tilenumber zoom) ] []
+
+tiles xs ys zoom =
+    List.map
+        (\ y -> div []
+             (List.map (\ x -> tileImg zoom (TileNumber x y)) xs))
+        ys

frontend/tests/PointTest.elm

@@ -1,6 +1,7 @@
 module PointTest exposing (specs)
 
-import Point exposing (Point, Pos, downsample, subseq)
+import Point exposing (Point, downsample, subseq)
+import Pos exposing (Pos)
 import Test exposing (..)
 import Expect exposing (Expectation)