class_name AtlasMapProtocol
## AtlasLayerRequest/Response, StarMapRequest/Response, CityNamesRequest/Response
## codec — factored out of protocol.gd (T-1118) to stay under gdlint's
## max-file-lines cap, same rationale + shape as browse_protocol.gd
## (T-1131/T-1133): `mp` (the loaded messagepack.gd module) is passed in
## rather than reloaded here — protocol.gd's _mp() already owns that load().
##
## Protocol delegates every one of these under the SAME public name
## (Protocol.atlas_response_from_raw(), Protocol.encode_star_map_request(),
## etc.) via its _amp() accessor — external callers (sim_bridge.gd,
## test_atlas_overlays.gd, test_atlas_data_delivery.gd) are unaffected by the
## move; only where the body lives changed.


## Encode an AtlasLayerRequest (#969, D-225) for the layer-stream proxy.
## A bare map {body_id, up_to} — NOT the Vec<PlayerInput> array — so the server's
## frame demux routes it to the atlas proxy. up_to is a CascadeLayer unit variant
## (bare string: "Heightmap" | "Topography").
##
## `window_center`/`window_n` (T-1138, D-226 T-1124 amendment §1): the windowed
## district-resolution regional-map query. Both are OMITTED from the encoded
## map (not sent as null) when window_center is null — this is what makes
## `#[serde(default)]` on the Rust side decode absence as `window_center: None`
## for every whole-body-only caller (request_atlas_layers()'s existing call
## sites), byte-identical to pre-T-1138 wire traffic. window_center is a
## DistrictPos, wire-encoded as the same [row, col] int-pair convention every
## other position field on this channel already uses (road_graph node
## positions, settlement positions, Layer-1 river-cell positions) — there is
## no separate DistrictPos struct-map on the wire, just a 2-element array.
## window_n is left unclamped here — §1 is explicit the server clamps to
## [1, DISTRICT_WINDOW_MAX_N] itself and never trusts the wire value; the
## client-side default/cap constants (DISTRICT_WINDOW_DEFAULT_N/MAX_N) live on
## the regional-window viewer, not duplicated into the codec.
##
## `window_min_wl_m` (T-1150): the octave cutoff, in whole metres. OMITTED
## (not sent as 0) when at its default — struct/key plumbing, byte-compatible
## with every existing caller that doesn't pass it.
##
## `window_granularity_v2` (T-1152, R5 redesign — see
## server/src/atlas/layer_proxy.rs's `WindowGranularity` doc): the derivation
## granularity, a plain STRING variant tag ("Quarter" | "District" |
## "Region"), matching `RoadNodeKind`'s existing wire precedent on this same
## carrier (a bare `#[derive(Serialize, Deserialize)]` enum with no
## `#[serde(rename_all)]` — rmp_serde encodes the Rust variant NAME verbatim,
## not an integer discriminant). OMITTED (not sent as "") when
## `window_granularity_v2` is the empty string — `#[serde(default)]` on the
## Rust side decodes absence as `None`, resolving to District (the default
## rung).
##
## **T-1159:** the legacy `window_granularity: int` field this codec used to
## also encode (T-1150's finer-than-district-only `u32` wire encoding) is
## retired — `window_granularity_v2` fully shadowed it since T-1152, and no
## caller in this codebase (nor any external client — single-repo
## client/server pair) ever sent it as anything but the byte-compatible
## default.
##
## **Quantization split (PR #191 review, Hoshe 1 / Tyre C3):** `window_min_wl_m`
## is sent HERE as a raw, unquantized value — this codec does NOT snap it to
## the design doc §5 fixed band set. The SERVER is the one place quantization
## happens (`serve_district_window` → `quantize_min_wl_m`, `layer_proxy.rs`):
## it snaps every request's value to the nearest band before touching the
## cache key or the echo, so a caller here is free to send a
## viewport-continuous estimate (e.g. `E/C` from the rung-selection rule) —
## don't pre-quantize client-side, it would just duplicate logic the server
## already owns and could drift out of sync with it.
static func encode_atlas_layer_request(
	mp,
	body_id: String,
	up_to: String = "Topography",
	window_center: Variant = null,
	window_n: int = 0,
	window_min_wl_m: int = 0,
	window_granularity_v2: String = ""
) -> PackedByteArray:
	var msg := {"body_id": body_id, "up_to": up_to}
	if window_center != null:
		var center: Vector2i = window_center
		msg["window_center"] = [center.x, center.y]
		msg["window_n"] = window_n
		if window_min_wl_m != 0:
			msg["window_min_wl_m"] = window_min_wl_m
		if not window_granularity_v2.is_empty():
			msg["window_granularity_v2"] = window_granularity_v2
	var result = mp.encode(msg)
	if result.status != null:
		push_error("Protocol: encode_atlas_layer_request failed: %s" % result.status)
		return PackedByteArray()
	return result.value


## Build an AtlasLayerResponse from an already-decoded raw value. Returns null
## if it is not an atlas response (no "status" key).
## road_graph/settlements (T-960): passthrough fields for the L2 road/rail
## graph and L3 settlement placements, mirroring the district_grid precedent
## (T-1046) — raw decoded maps/arrays, no further client-side reshaping.
## region_grid (T-1113/T-1118): the region climate grid, same passthrough
## pattern. quarter_footprints (T-1119, D-226 T-1112 amendment touch point 3):
## the L4 quarter-footprint aggregates, same passthrough pattern —
## QuarterFootprintLayer.entries is a BTreeMap<u64, QuarterFootprintEntry> on
## the wire, decoding to a Dictionary with int keys (city_id), no reshaping.
## district_window (T-1138, D-226 T-1124 amendment §2): the windowed
## DistrictWindowLayer — a DISTINCT payload by design (keyed on the request's
## (body, center, n), not the body alone), but the wire passthrough is the
## same shape as every sibling: raw.get() with no reshaping, `None` on the
## wire decodes to GDScript `null` exactly like every other Option field here.
## The response's `center`/`n` echo (inside the layer dict itself) is the
## client's race-condition/staleness guard (§2) — read by the window cache,
## not unwrapped here. `granularity_v2` (T-1152) rides inside the same dict,
## a bare string variant tag ("Quarter"/"District"/"Region") — no separate
## top-level unwrap needed, it passes through with everything else.
## Key names "road_graph"/"settlements"/"region_grid"/"quarter_footprints"/
## "district_window" are the CONFIRMED wire contract — identical to
## server/src/atlas/layer_proxy.rs AtlasLayerResponse's field names
## (region_grid pinned 2026-07-14, quarter_footprints pinned 2026-07-18,
## district_window per the D-226 T-1124 amendment §2 struct; round-tripped by
## test_atlas_overlays.gd/test_atlas_data_delivery.gd and the server's msgpack
## round-trip tests). This remains the one client-side spot to touch if the
## contract ever changes.
static func atlas_response_from_raw(raw: Variant) -> Variant:
	if not raw is Dictionary or not raw.has("status"):
		return null
	var status_raw = raw["status"]
	var status := ""
	var error := ""
	if status_raw is String:
		status = status_raw
	elif status_raw is Dictionary and status_raw.has("Error"):
		status = "Error"
		error = str(status_raw["Error"])
	return {
		"body_id": raw.get("body_id", ""),
		"status": status,
		"error": error,
		"layer1": raw.get("layer1"),
		"district_grid": raw.get("district_grid"),
		"road_graph": raw.get("road_graph"),
		"settlements": raw.get("settlements"),
		"region_grid": raw.get("region_grid"),
		"quarter_footprints": raw.get("quarter_footprints"),
		"district_window": raw.get("district_window"),
	}


## Decode a status enum shared by StarMapStatus/CityNamesStatus/AtlasLayerStatus
## shape: a unit variant is a bare string ("Ready", "SolExcluded", …); the one
## data variant (Error(String)) is a single-key map {"Error": "message"}.
## Returns {"status": String, "error": String} (error empty unless Error).
static func _decode_status_field(status_raw: Variant) -> Dictionary:
	if status_raw is String:
		return {"status": status_raw, "error": ""}
	if status_raw is Dictionary and status_raw.has("Error"):
		return {"status": "Error", "error": str(status_raw["Error"])}
	return {"status": "", "error": ""}


## Encode a StarMapRequest (T-949, D-010) for the Reach-level star-map proxy.
## `star_map: true` is the mandatory discriminator field the server's demux
## matches on (dudley-atlas-server contract, 2026-07-14) — always send it,
## never omit it, or the frame can't be routed.
static func encode_star_map_request(mp) -> PackedByteArray:
	var msg := {"star_map": true}
	var result = mp.encode(msg)
	if result.status != null:
		push_error("Protocol: encode_star_map_request failed: %s" % result.status)
		return PackedByteArray()
	return result.value


## Build a StarMapResponse from an already-decoded raw value. Returns null if
## it is not a star-map response (no "status" key). `data` is a verbatim
## MessagePack re-encoding of star_map_data.json's own top-level shape
## (`_meta`/`nodes`/`edges`) — unwrapped here so callers (SystemIndex) see the
## same {"nodes": [...]} shape they'd have gotten from the raw file, and never
## need to know about the status/data envelope.
static func star_map_response_from_raw(raw: Variant) -> Variant:
	if not raw is Dictionary or not raw.has("status"):
		return null
	var decoded_status := _decode_status_field(raw.get("status"))
	var nodes: Array = []
	if decoded_status["status"] == "Ready":
		var data: Variant = raw.get("data")
		if data is Dictionary:
			nodes = data.get("nodes", [])
	return {"status": decoded_status["status"], "error": decoded_status["error"], "nodes": nodes}


## Encode a CityNamesRequest (T-949, D-223/D-236) for one body's atlas
## city-name pool. `city_names: true` is the mandatory discriminator field
## (same contract as StarMapRequest) — without it the request is structurally
## ambiguous with a malformed AtlasLayerRequest (missing `up_to`). Sent for
## every body INCLUDING Sol — the server itself reports SolExcluded for those
## (D-236) as a defensive backstop; atlas_viewer.gd's own guard is expected to
## make that path rare, not load-bearing on its own.
static func encode_city_names_request(mp, body_id: String) -> PackedByteArray:
	var msg := {"city_names": true, "body_id": body_id}
	var result = mp.encode(msg)
	if result.status != null:
		push_error("Protocol: encode_city_names_request failed: %s" % result.status)
		return PackedByteArray()
	return result.value


## Build a CityNamesResponse from an already-decoded raw value. Returns null
## unless it carries both "body_id" and "status". `cities` is a flat array of
## {city_id, name, is_capital} — no position (that comes from SettlementLayer,
## T-960's gen_l3_settlements). status is one of "Ready" | "SolExcluded" |
## "Error" (see _decode_status_field) — SolExcluded means the caller must fall
## back to the legacy markers.json read for that body (D-236).
static func city_names_response_from_raw(raw: Variant) -> Variant:
	if not raw is Dictionary or not raw.has("body_id") or not raw.has("status"):
		return null
	var decoded_status := _decode_status_field(raw.get("status"))
	return {
		"body_id": str(raw.get("body_id", "")),
		"status": decoded_status["status"],
		"error": decoded_status["error"],
		"cities": raw.get("cities", []),
	}