-- =====================================================================
-- lib-core.interaction — Proximity-Trigger + Action-Dispatch (P.0)
-- See: meta/docs/superpowers/specs/2026-05-10-p0-lib-interaction-design.md
--
-- Scope: register proximity-triggers (target-point + range + action-name +
-- callback), dispatch nearest matching trigger per action_name when action
-- fires. Was-pressed semantics (single-frame edge, no hold-repeat).
-- DEPRECATED-MVP for: AABB-targets, action-effect-pipeline, visual-feedback,
-- action-cycling, hold-charging, per-action-resolution-override,
-- callback-pcall-wrap, target-entity-binding, range-shape-variants.
-- =====================================================================
local input    = require("lib-core.input")
local spatial  = engine.spatial

local M = {}

-- module-local state
local triggers      = {}   -- array of trigger records
local next_id       = 1

local function find_index_by_id(id)
    for i, t in ipairs(triggers) do
        if t.id == id then return i end
    end
    return nil
end

function M.register(target_x, target_y, range, action_name, callback)
    if type(target_x) ~= "number" or type(target_y) ~= "number" then
        error("interaction.register: target_x and target_y must be numbers")
    end
    if type(range) ~= "number" or range <= 0 then
        error("interaction.register: range must be a positive number")
    end
    if type(action_name) ~= "string" or action_name == "" then
        error("interaction.register: action_name must be a non-empty string")
    end
    if type(callback) ~= "function" then
        error("interaction.register: callback must be a function")
    end
    local id = next_id
    next_id = next_id + 1
    triggers[#triggers + 1] = {
        id          = id,
        target_x    = target_x,
        target_y    = target_y,
        range       = range,
        action_name = action_name,
        callback    = callback,
    }
    return id
end

function M.unregister(id)
    local idx = find_index_by_id(id)
    if idx then
        table.remove(triggers, idx)
    end
    -- silent no-op if id not found
end

function M.update(actor_x, actor_y)
    if type(actor_x) ~= "number" or type(actor_y) ~= "number" then
        error("interaction.update: actor_x and actor_y must be numbers")
    end

    -- group-by-action_name: { action_name -> { nearest_trigger, nearest_dist } }
    local groups = {}
    for _, t in ipairs(triggers) do
        local d = spatial.distance(actor_x, actor_y, t.target_x, t.target_y)
        if d <= t.range then
            local g = groups[t.action_name]
            if not g or d < g.dist then
                groups[t.action_name] = { trigger = t, dist = d }
            end
        end
    end

    -- fire nearest per action_name if action was pressed this frame
    for action_name, g in pairs(groups) do
        if input.was_action_pressed(action_name) then
            local t = g.trigger
            t.callback({
                actor_x     = actor_x,
                actor_y     = actor_y,
                target_x    = t.target_x,
                target_y    = t.target_y,
                distance    = g.dist,
                trigger_id  = t.id,
                action_name = action_name,
            })
        end
    end
end

function M.list()
    local out = {}
    for i, t in ipairs(triggers) do
        out[i] = {
            id          = t.id,
            target_x    = t.target_x,
            target_y    = t.target_y,
            range       = t.range,
            action_name = t.action_name,
        }
    end
    return out
end

function M.trigger_count()
    return #triggers
end

-- DEPRECATED-MVP: AABB-targets (range as rect)            -- footprint-items slice
-- DEPRECATED-MVP: action-effect-pipeline integration      -- post-P.0 action-pipeline activation
-- DEPRECATED-MVP: visual-feedback / moodlet UI hint        -- UI slice
-- DEPRECATED-MVP: action-cycling (multi-action UX)         -- UI + multi-action-UX slice
-- DEPRECATED-MVP: hold-vs-press semantics (charge, hold)   -- charge-action slice
-- DEPRECATED-MVP: per-action-resolution-override           -- multi-pickup slice
-- DEPRECATED-MVP: callback pcall-wrap (resilience)         -- E.9 resilience refactor
-- DEPRECATED-MVP: target-entity-binding (entity-handle)    -- actor / composition slice
-- DEPRECATED-MVP: range-shape variants (cone, line, AABB)  -- combat / vision-cone slice

return M