-- Chest backend
-- Currently just the one for Dragon. Will not actually work yet.

local w = require "lib"
local d = require "luadash"
local fuzzy_match = require "fuzzy"

local conf = w.load_config({
    "buffer_internal",
    "buffer_external"
}, {
    modem_internal = nil
})

local BUFFER_OUT_SLOT = 1
local BUFFER_IN_SLOT = 2

-- Find all chests or shulker boxes
local inventories = d.map_with_key(w.find_peripherals(function(type, name, wrapped)
    return string.find(name, "chest") or string.find(name, "shulker")
end, conf.modem_internal), function(_, p) return p.name, p.wrapped end)

local info_cache = {}

-- Gets the display name of the given item (in the given chest peripheral & slot)
-- If its name is not cached, cache it.
-- If it is, just return the cached name
local function cache(item, chest, slot)
    local idx = w.get_internal_identifier(item)
    
    if info_cache[idx] then
        return info_cache[idx]
    else
		local info = chest.getItemMeta(slot)
        info_cache[idx] = { display_name = info.displayName, max_count = info.maxCount }
		return info_cache[idx]
    end
end

local index = {}
-- Update the index for the given peripheral
local function update_index_for(name)
    local inv = inventories[name]
    local data = inv.list()
    
    for slot, item in pairs(data) do
        data[slot] = w.to_wyvern_item(data[slot])
        w.join(data[slot], cache(data[slot], inv, slot))
    end
    
    index[name] = data
    
    print("Indexed " .. name .. ".")
end

-- Reindex all connected inventories
local function update_index()
    print "Full indexing started."
	for n in pairs(inventories) do
        update_index_for(n)
		sleep()
	end
	print "Full indexing complete."
end

-- Finds all items matching a certain predicate.
-- Returns a table of tables of { name, slot, item }
local function find(predicate)
    local ret = {}
    for inventory, items in pairs(index) do
        for slot, item in pairs(items) do
            local ok, extra = predicate(item) -- allow predicates to return some extra data which will come out in resulting results
            if ok then
                table.insert(ret, { location = { inventory = inventory, slot = slot }, item = item, extra = extra })
            end
        end
    end
    return ret
end

-- Finds space in the chest system. Returns the name of an inventory which has space.
local function find_space(item)
    local locations = {}
    local quantity = item.count
    for name, items in pairs(index) do
        for i = 1, inventories[name].size() do
            local item_in_slot = index[name][i]
            if not item_in_slot or (item_in_slot.ID == item.ID and item_in_slot.meta == item.meta and item_in_slot.NBT_hash == item.NBT_hash) then -- slot is free or contains same type of item
                local available_space = item.max_count
                if item_in_slot then available_space = available_space - item_in_slot.count end
                if available_space > 0 then 
                    quantity = quantity - available_space
                    table.insert(locations, { inventory = name, slot = i })
                end
                if quantity <= 0 then return locations end
            end
        end
    end
    error(w.errors.make(w.errors.NOSPACE))
end

local function find_by_ID_meta_NBT(ID, meta, NBT_hash)
    return find(function(item)
        return 
        (not meta or item.meta == meta) and -- if metadata provided, ensure match
        (not ID or item.ID == ID) and -- if internal name provided, ensure match
        (not NBT_hash or item.NBT_hash == NBT_hash) -- if NBT hash provided, ensure match
    end)
end

local function search(query, exact)
    local results = find(function(item)
        if exact then
            return string.lower(query) == string.lower(item.display_name), 0
        else
            local match, best_start = fuzzy_match(item.display_name, query)
            if best_start ~= nil and match > 0 then return true, match end
        end
    end)
    return d.sort_by(results, function(x) return x.extra end) -- sort returned results by closeness to query
end

-- Retrives items from a location in storage and puts them in the buffer
local function fetch_by_location(loc, limit)
    local peripheral_name, slot, limit = loc.inventory, loc.slot, limit or 64
    return peripheral.call(conf.buffer_internal, "pullItems", peripheral_name, slot, limit, BUFFER_OUT_SLOT)
end

-- Clears out the buffer into storage.
local function clear_buffer()
    for i = 1, peripheral.call(conf.buffer_internal, "size") do
        local space_location = find_space()
        if not space_location then error("Storage capacity reached. Please add more chests or shulker boxes.") end
        peripheral.call(conf.buffer_internal, "pushItems", space_location, i)
        os.queueEvent("reindex", space_location)
        sleep()
    end
end

local function update_slot(inv, slot, by, stack)
    if index[inv][slot] then 
        index[inv][slot].count = index[inv][slot].count - by
        if index[inv][slot].count == 0 then index[inv][slot] = nil
        elseif index[inv][slot].count < 0 then os.queueEvent "reindex" error "Index inconsistency error." end
    else
        index[inv][slot] = stack
    end
end

local function server(command)
    if command.type == "buffers" then -- Sends the external address of the buffer
        return conf.buffer_external
    elseif command.type == "reindex" then
        os.queueEvent "reindex"
    elseif command.type == "extract" then
        local result = find_by_ID_meta_NBT(command.ID, command.meta, command.NBT_hash)
        
        local stacks = {}
        
        -- Check if we have an item, and its stack is big enough; otherwise, send back an error.
        local quantity_to_fetch_remaining, items_moved_from_storage = command.quantity or 0, 0
        repeat
            local stack_to_pull = table.remove(result, 1)
            
            if not stack_to_pull then 
                error(w.errors.make(w.errors.NOITEMS, { type = w.get_internal_identifier(command), quantity = quantity_to_fetch_remaining }))
            end
            
            table.insert(stacks, stack_to_pull)
            items_moved_from_storage = items_moved_from_storage + fetch_by_location(stack_to_pull.location, command.quantity)

            -- update index
            local location = stack_to_pull.location
            update_slot(location.inventory, location.slot, items_moved_from_storage, stack_to_pull)
        until items_moved_from_storage >= quantity_to_fetch_remaining
        
        if command.destination_inventory then
            -- push items to destination
            items_moved_to_destination = peripheral.call(conf.buffer_external, "pushItems", command.destination_inventory, BUFFER_OUT_SLOT, command.quantity, command.destination_slot)
            
            -- If destination didn't accept all items, clear out the buffer.
            if items_moved_to_destination < items_moved_from_storage then
                clear_buffer()
            end
        end
        
        return { moved = items_moved_to_destination or items_moved_from_storage, stacks = stacks_moved }
    elseif command.type == "insert" then
        if command.from_inventory and command.from_slot then
            peripheral.call(conf.buffer_external, "pullItems", command.from_inventory, command.from_slot, command.quantity, BUFFER_IN_SLOT) -- pull from from_inventory to buffer
        end
        
        local quantity = peripheral.call(conf.buffer_external, "pullItems", conf.buffer_external, BUFFER_IN_SLOT, 64, BUFFER_IN_SLOT) -- send to itself to get stack size

        local raw_item = peripheral.call(conf.buffer_internal, "getItemMeta", BUFFER_IN_SLOT)
        if not raw_item or quantity == 0 then return end
        local item = w.to_wyvern_item(raw_item)

        w.join(item, cache(item, peripheral.wrap(conf.buffer_internal), BUFFER_IN_SLOT))
        local space_locations = find_space(item) -- command contains item-related stuff

        local moved = 0

        for _, loc in pairs(space_locations) do
            local moved_now = peripheral.call(conf.buffer_internal, "pushItems", loc.inventory, BUFFER_IN_SLOT, 64, loc.slot) -- push from buffer to free space
            update_slot(loc.inventory, loc.slot, -moved_now, item)
            moved = moved + moved_now
        end
        
        return { moved = moved }
    elseif command.type == "search" then
        return w.collate_stacks(d.map(search(command.query, command.exact), function(x) return x.item end))
    elseif command.type == "list" then
        return index
    end
end

local function indexer_thread()
    while true do
        local _, inventory = os.pullEvent "reindex"
        if inventory then update_index_for(inventory) else update_index() end
    end
end

w.init()
parallel.waitForAll(function() os.queueEvent("reindex") w.serve(server, "storage") end, indexer_thread)