randy
16e06b2ffe
Not going to be used — drop src-tauri/ and all references to it in the docs. MapTool stays a plain Sinatra web app for now.
117 lines
4.4 KiB
Plaintext
117 lines
4.4 KiB
Plaintext
= Architecture
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:toc:
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:toclevels: 2
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== Overview
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MapTool is a Sinatra web application, served locally by Puma and
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opened in a browser.
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== Directory layout
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[cols="1,3"]
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|===
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| Path | Purpose
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| `app.rb`, `config.ru`
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| Sinatra application and Rack entry point.
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| `config/puma.rb`
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| Puma server configuration (binds to `127.0.0.1` only — the app is
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local-only, not exposed on the network).
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| `public/`, `views/`
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| Frontend assets and Sinatra templates. The map view uses MapLibre GL
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JS, rendering vector tiles.
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| `public/vendor/`
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| Third-party frontend libraries, vendored (not loaded from a CDN) so
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the app also works with no internet access. See
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`docs/third-party-notices.adoc`.
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| `data/`
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| Local, gitignored data files, e.g. `offline.pmtiles`.
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| `docs/`
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| Project documentation, in AsciiDoc.
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|===
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== Offline maps
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Map data is vector, not raster: the app ships
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https://maplibre.org[MapLibre GL JS] (vendored, see below) and the map
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view (`public/js/map.js`) offers two styles:
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* *Online* — a full hosted vector style,
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https://tiles.openfreemap.org/styles/liberty[OpenFreeMap "liberty"],
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requires internet access.
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* *Offline* — built at runtime from a local
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https://github.com/protomaps/PMTiles[PMTiles] archive at
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`data/offline.pmtiles`, served as-is (see below) at
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`/tiles/offline.pmtiles`, decoded client-side by
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https://github.com/protomaps/PMTiles[pmtiles.js] registered as a
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`pmtiles://` protocol handler, and styled with base layers from
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https://github.com/protomaps/basemaps[protomaps-themes-base].
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`GET /api/offline-tiles` reports whether `data/offline.pmtiles` is
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present (`{"available": true|false}`); the frontend uses it once, on
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load, to default to the offline style when local tile data exists —
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otherwise it defaults to the online style. Either way, the layer
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toggle in the top-left of the map lets the user switch manually.
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PMTiles is a single, self-indexed file, which is why this needs no
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tile-decoding logic on the server: `app.rb`'s `/tiles/offline.pmtiles`
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route (`send_file`, which Sinatra serves with HTTP range-request
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support) just returns byte ranges of the file; pmtiles.js in the
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browser reads the archive's own directory and requests only the bytes
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it needs for the tiles on screen.
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=== Known limitation: no offline text labels
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The offline style only renders `protomaps-themes-base`'s non-label
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layers (roads, buildings, land use, water — no place names or street
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labels). Label rendering in MapLibre needs a "glyphs" server serving
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font PBF ranges, which would mean vendoring a font glyph set locally
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too; that has not been done, to keep the initial scope manageable.
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Revisit this if labelled offline maps turn out to matter in practice.
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No PMTiles file ships with the repository — it is expected to be
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supplied locally (see `docs/development.adoc`) and stays gitignored
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because such extracts are typically large binary files.
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== Weather radar overlay
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`public/js/radar.js` adds a "Radar" map control that overlays recent
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precipitation radar from https://www.rainviewer.com[RainViewer]'s free
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public API (no API key required). Enabling it:
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. Fetches `https://api.rainviewer.com/public/weather-maps.json`,
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which lists RainViewer's past radar frames (fixed 10-minute
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cadence, at most 13 covering the last 120 minutes).
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. Takes the most recent 7 (last ~60 minutes — the same default as
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the https://github.com/jpettitt/weather-radar-card[Home Assistant
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weather-radar-card], for a consistent feel with that setup) and
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adds one MapLibre raster source/layer per frame, all pre-loaded but
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only the current frame's `raster-opacity` non-zero.
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. Animates by toggling that opacity across frames on an interval
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(play/pause + a scrub slider), rather than swapping tiles in and out
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— avoids reloading tiles on every step.
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Tile URL: `{host}{frame.path}/256/{z}/{x}/{y}/2/1_0.png` — `2` is
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RainViewer's "Universal Blue" color scheme, `1` enables their
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smoothing, `0` disables the snow overlay. `host` and each frame's
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`path` come from the API response.
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Since `map.setStyle()` (switching Online/Offline) tears down all
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custom sources and layers, the control listens for `style.load` and
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re-adds the radar layers if the overlay was on.
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This is a live, online-only overlay — it always needs internet access
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and is unrelated to the offline PMTiles basemap above. Per RainViewer's
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terms, the API is free for personal/non-commercial use.
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== Networking
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The Sinatra server only binds to `127.0.0.1`. It is not meant to be
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reachable from other machines.
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