-- =====================================================================
-- lib-core.render v0.2.0 — Tile-Grid + Entity Rendering
-- See: meta/docs/superpowers/specs/2026-05-09-p0-lib-render-design.md
--      meta/docs/superpowers/specs/2026-06-09-phase-A-...
--
-- v0.2.0 additions:
--   - draw_entities(filter) — tag-based entity-render via composition.
--     Supports two sprite-property paths and a fallback:
--       (1) sprite_atlas + sprite_uv.{x,y,w,h} → atlas-sub-rect render
--           via engine.render.draw_sprite_transform
--       (2) sprite_color + sprite_w + sprite_h → colored rect
--           via engine.render.draw_rect
--       (3) none of above → magenta fallback rect (debug-visible)
--     `position.x` and `position.y` are visual CENTER for all modes.
--     Texture-handles for sprite_atlas paths are cached internally.
--
-- v0.1.0 API unverändert: draw_map.
-- =====================================================================

local maps        = require("lib-core.maps")
local composition = require("lib-core.composition")

local FALLBACK_COLOR = {255, 0, 255}  -- magenta — "missing color" debug-marker

-- Texture-handle cache for sprite_atlas paths. lazy-loaded on first
-- draw_entities call that references the path. Lives for the engine
-- process; no eviction in v0.2.0.
local atlas_cache = {}

-- Fallback-rect size (px) for entities without any sprite-property.
-- Magenta is the debug-marker; size is small enough to be intrusive
-- without dominating the screen.
local FALLBACK_RECT_SIZE = 16

local function load_atlas(path)
    local h = atlas_cache[path]
    if h ~= nil then return h end
    h = engine.asset.load_texture(path)
    atlas_cache[path] = h
    return h
end

-- Reads tile-color from TileType-table; fallback to magenta if missing or malformed.
local function tile_color(tile_type)
    local c = tile_type.color
    if type(c) ~= "table" or #c < 3 then return FALLBACK_COLOR end
    return c
end

local M = {}

-- Iterates current (or specified) map's tiles, draws a colored rect per tile.
-- Must be called from inside a render hook (engine.render.* enforces this).
-- Returns the number of tiles drawn (for smoke verification + debug).
function M.draw_map(map_id)
    local size = maps.size(map_id)
    local tile_size = maps.tile_size(map_id)
    local count = 0
    for ty = 0, size.h - 1 do
        for tx = 0, size.w - 1 do
            local t = maps.tile_at(map_id, tx, ty)
            if t ~= nil then
                local c = tile_color(t)
                local color = engine.render.rgb(c[1], c[2], c[3])
                engine.render.draw_rect(
                    tx * tile_size, ty * tile_size,
                    tile_size, tile_size,
                    color)
                count = count + 1
            end
        end
    end
    return count
end

-- ---------------------------------------------------------------------
-- v0.2.0 — Entity Rendering
-- ---------------------------------------------------------------------

-- Try to read an entity-property as a number; returns nil if absent
-- (instead of the engine's typed default), so callers can branch on
-- presence without conflating with default-zero.
--
-- engine.entity:get_property currently returns nil only if the property
-- isn't declared at all; declared-with-default-value yields the default.
-- v0.1 composition declares whatever's in the template — any property
-- not declared is genuinely absent and yields the engine fallback.
local function get_num(entity, key)
    local v = entity:get_property(key)
    if type(v) == "number" then return v end
    return nil
end

local function get_str(entity, key)
    local v = entity:get_property(key)
    if type(v) == "string" and v ~= "" then return v end
    return nil
end

-- Draws all entities tagged with `filter.tag`.
-- Filter shape: { tag = "<string>" } — anything else is loud-error.
-- Returns the number of entities drawn (for smoke verification).
function M.draw_entities(filter)
    if type(filter) ~= "table" then
        error("render.draw_entities: filter must be a table with field 'tag'")
    end
    if type(filter.tag) ~= "string" or filter.tag == "" then
        error("render.draw_entities: filter.tag must be a non-empty string " ..
              "(other filter-shapes deferred — see Phase-A Spec A-Q3)")
    end

    local list = composition.list_by_tag(filter.tag)
    local count = 0
    for _, e in ipairs(list) do
        local px = get_num(e, "position.x")
        local py = get_num(e, "position.y")
        if px ~= nil and py ~= nil then
            local atlas = get_str(e, "sprite_atlas")
            if atlas ~= nil then
                -- Path (1): atlas sub-rect.
                local uvx = get_num(e, "sprite_uv.x")
                local uvy = get_num(e, "sprite_uv.y")
                local uvw = get_num(e, "sprite_uv.w")
                local uvh = get_num(e, "sprite_uv.h")
                if uvx and uvy and uvw and uvh then
                    local tex = load_atlas(atlas)
                    -- position is visual-center: origin = uv center
                    engine.render.draw_sprite_transform(
                        tex, px, py, 0, 1, 1, uvw / 2, uvh / 2,
                        0xFFFFFFFF, uvx, uvy, uvw, uvh)
                    count = count + 1
                end
            else
                local sc = e:get_property("sprite_color")
                local sw = get_num(e, "sprite_w")
                local sh = get_num(e, "sprite_h")
                if type(sc) == "number" and sw and sh then
                    -- Path (2): colored rect, position = visual-center
                    engine.render.draw_rect(
                        px - sw / 2, py - sh / 2, sw, sh, sc)
                    count = count + 1
                else
                    -- Path (3): magenta fallback
                    local fbcol = engine.render.rgb(
                        FALLBACK_COLOR[1], FALLBACK_COLOR[2], FALLBACK_COLOR[3])
                    local s = FALLBACK_RECT_SIZE
                    engine.render.draw_rect(px - s / 2, py - s / 2, s, s, fbcol)
                    count = count + 1
                end
            end
        end
    end
    return count
end

-- Forward-compat stubs for later slices (kept as comments to avoid table-pollution):
-- DEPRECATED-MVP: function M.set_camera(camera)       -- lib-core.camera slice
-- DEPRECATED-MVP: function M.push_layer(name, order)  -- multi-layer slice
-- DEPRECATED-MVP: function M.register_pass(...)       -- post-processing slice (spec §6)
-- DEPRECATED-MVP: function M.set_clear_color(rgb)     -- per-layer clear-color (spec §4)

return M