-- =====================================================================
-- lib-core.command v0.1.0 — Move-Commands + Per-Frame-Execution
-- See: meta/docs/superpowers/specs/2026-05-14-p3-7-lib-command-design.md
--
-- Handle-Registry mit get_pos + set_pos + speed (extending selection-pattern
-- mit write-callback). Lib-driven auto-wire via action-binding (press-edge,
-- analog selection). Per-frame movement: direction-normalize + step-vs-distance
-- → arrive-snap. Move-only in v0.1.0; context-sensitive dispatch deferred.
--
-- DEPRECATED-MVPs siehe Spec §7 + inline-comments unten.
-- =====================================================================

local input  = require("lib-core.input")
local camera = require("lib-core.camera")

-- Registry: array of {handle, get_pos, set_pos, speed}.
local units = {}
local next_handle = 1

-- Active commands: handle → {type, target_x, target_y}.
local active_commands = {}

-- Bindings.
local move_action     = nil
local target_provider = nil

-- Settings.
local arrive_threshold = 2     -- px
local enabled_flag     = true

-- ---------- internal helpers ----------

local function check_function(arg_name, value)
    if type(value) ~= "function" then
        error(string.format("command.%s: must be a function", arg_name))
    end
end

local function check_positive(arg_name, value)
    if type(value) ~= "number" or value <= 0 then
        error(string.format("command.%s: must be positive number", arg_name))
    end
end

local function check_string(arg_name, value)
    if type(value) ~= "string" or value == "" then
        error(string.format("command.%s: must be non-empty string", arg_name))
    end
end

local function find_unit_index(handle)
    for i, u in ipairs(units) do
        if u.handle == handle then return i end
    end
    return nil
end

local function find_unit(handle)
    for _, u in ipairs(units) do
        if u.handle == handle then return u end
    end
    return nil
end

-- ---------- public API ----------

local M = {}

-- Registry

function M.register(get_pos_fn, set_pos_fn, speed)
    check_function("register.get_pos_fn", get_pos_fn)
    check_function("register.set_pos_fn", set_pos_fn)
    check_positive("register.speed", speed)
    local h = next_handle
    next_handle = next_handle + 1
    units[#units + 1] = {
        handle  = h,
        get_pos = get_pos_fn,
        set_pos = set_pos_fn,
        speed   = speed,
    }
    return h
end

function M.unregister(handle)
    local idx = find_unit_index(handle)
    if idx then
        table.remove(units, idx)
        active_commands[handle] = nil   -- clear dangling command
    end
    -- silent no-op on unknown handle
end

function M.count_registered()
    return #units
end

-- Per-Unit Speed

function M.set_speed(handle, n)
    local u = find_unit(handle)
    if u == nil then
        error("command.set_speed: handle " .. tostring(handle) .. " not registered")
    end
    check_positive("set_speed.n", n)
    u.speed = n
end

function M.speed(handle)
    local u = find_unit(handle)
    if u == nil then
        error("command.speed: handle " .. tostring(handle) .. " not registered")
    end
    return u.speed
end

-- Command-Issue (Programmatic)

function M.move_to(handles, target_x, target_y)
    if type(handles) ~= "table" then
        error("command.move_to: handles must be a table (array of handles)")
    end
    if type(target_x) ~= "number" or type(target_y) ~= "number" then
        error("command.move_to: target_x and target_y must be numbers")
    end
    -- Validate ALL handles BEFORE mutating any state.
    for _, h in ipairs(handles) do
        if find_unit(h) == nil then
            error("command.move_to: handle " .. tostring(h) .. " not registered")
        end
    end
    for _, h in ipairs(handles) do
        active_commands[h] = { type = "move", target_x = target_x, target_y = target_y }
    end
end

function M.cancel(handle)
    active_commands[handle] = nil   -- silent no-op
end

function M.cancel_all()
    active_commands = {}
end

-- Command-State-Query

function M.current(handle)
    local cmd = active_commands[handle]
    if cmd == nil then return nil end
    return { type = cmd.type, target_x = cmd.target_x, target_y = cmd.target_y }
end

function M.is_moving(handle)
    return active_commands[handle] ~= nil
end

-- Bindings

function M.bind_move_action(action_name)
    check_string("bind_move_action", action_name)
    move_action = action_name
end

function M.bind_target_provider(fn)
    check_function("bind_target_provider", fn)
    target_provider = fn
end

-- Settings

function M.set_arrive_threshold(n)
    check_positive("set_arrive_threshold", n)
    arrive_threshold = n
end

function M.arrive_threshold()
    return arrive_threshold
end

function M.set_enabled(b)
    if type(b) ~= "boolean" then
        error("command.set_enabled: must be boolean")
    end
    enabled_flag = b
end

function M.enabled()
    return enabled_flag
end

-- Per-Frame

function M.update(dt)
    if not enabled_flag then return end

    -- A) Input-Polling für Auto-Wire (press-edge):
    if move_action ~= nil and target_provider ~= nil then
        if input.was_action_pressed(move_action) then
            local handles = target_provider()
            if type(handles) == "table" and #handles > 0 then
                local mx, my = engine.input.get_mouse_pos()
                local wx, wy = camera.screen_to_world(mx, my)
                M.move_to(handles, wx, wy)
            end
        end
    end

    -- B) Movement-Tick: iterate active commands:
    for handle, cmd in pairs(active_commands) do
        local unit = find_unit(handle)
        if unit == nil then
            active_commands[handle] = nil   -- handle unregistered
        elseif cmd.type == "move" then
            local pos = unit.get_pos()
            if type(pos) == "table"
               and type(pos.x) == "number" and type(pos.y) == "number" then
                local dx = cmd.target_x - pos.x
                local dy = cmd.target_y - pos.y
                local dist = math.sqrt(dx * dx + dy * dy)
                local step = unit.speed * dt
                if dist <= arrive_threshold or step >= dist then
                    unit.set_pos(cmd.target_x, cmd.target_y)
                    active_commands[handle] = nil
                else
                    local ratio = step / dist
                    unit.set_pos(pos.x + dx * ratio, pos.y + dy * ratio)
                end
            end
            -- invalid pos return: skip frame (best-effort)
        end
    end
end

-- DEPRECATED-MVP: context-sensitive RMB dispatch (attack/harvest/follow per
--                 target-type) — own slice when 2nd command-type exists.
-- DEPRECATED-MVP: pathfinding (A* / nav-mesh) — own slice, P.4
-- DEPRECATED-MVP: stop-command via dedicated action — comes with attack slice
-- DEPRECATED-MVP: formation-move (offset keeping) — P.4 RTS-polish
-- DEPRECATED-MVP: command-queue (Shift+RMB waypoints) — own slice
-- DEPRECATED-MVP: path-move (waypoint-list as single target) — precursor to queue
-- DEPRECATED-MVP: per-command speed-multiplier (sprint, walk) — gameplay-driven
-- DEPRECATED-MVP: faction/ownership system (own vs enemy command-eligibility) — P.4+
-- DEPRECATED-MVP: observer pattern (on_command_complete callback) — UI-refresh
-- DEPRECATED-MVP: direction-smoothing (turn-rate, acceleration) — P.4 RTS-polish
-- DEPRECATED-MVP: collision-avoidance (units pushing each other) — P.4+

return M