-- ===================================================================

eregions.used       = {}
eregions.addabm_map = {}

-- ===================================================================

local eregions_addabm = function (efeature)
    if eregions.used [efeature] ~= nil then return end
       eregions.used [efeature] =  1

    local func = eregions.addabm_map [efeature]
    if func ~= nil then func() end
end

-- ===================================================================

-- Save the eregions table to a file

function eregions:save()
    local  datastr = minetest.serialize (self.eregions)
    if not datastr then
        minetest.log ("error",
            "[eregions] Failed to serialize eregion data")
        return
    end

    local file, err = io.open (eregions.filename, "w")
    if err then return err end
    file:write (datastr)
    file:close()
end

-- ===================================================================

-- Load the eregions table from the save file
function eregions:load()
    local file, err = io.open (eregions.filename, "r")
    if err then
        self.eregions = self.eregions or {}
        return err
    end

    self.eregions = minetest.deserialize (file:read ("*a"))
    if type(self.eregions) ~= "table" then
        self.eregions = {}
    end
    file:close()
    self:populateStore()

    for id, eregion in pairs (eregions.eregions) do
        eregions_addabm (eregion.efeature)
    end
end

-- ===================================================================

--- Checks an AreaStore ID.
-- Deletes the AreaStore (falling back to the iterative method)
-- and prints an error message if the ID is invalid.
-- @return Whether the ID was valid.

function eregions:checkAreaStoreId (sid)
    if not sid then
        minetest.log ("error", "AreaStore failed to find an ID for an "
            .."eregion. Falling back to iterative eregion checking.")
        self.store     = nil
        self.store_ids = nil
    end
    return sid and true or false
end

-- ===================================================================

-- Populates the AreaStore after loading, if needed.

function eregions:populateStore()
    if not rawget (_G, "AreaStore") then return end
    local store     = AreaStore()
    local store_ids = {}

    for id, eregion in pairs (eregions.eregions) do
        local sid = store:insert_area (eregion.pos1,
            eregion.pos2, tostring (id))
        if not self:checkAreaStoreId (sid) then return end
        store_ids [id] = sid
    end

    self.store     = store
    self.store_ids = store_ids
end

-- ===================================================================

-- Finds the first usable index in a table
-- Eg: {[1]=false,[4]=true} -> 2

local function findFirstUnusedIndex (t)
    local  i = 0
    repeat i = i + 1
    until t [i] == nil
    return i
end

-- ===================================================================

local eregions_addabm_lavagel = function()

    minetest.register_abm ({
        nodenames = {
            "default:lava_flowing" ,
            "default:lava_source"  ,
        } ,
        catch_up  = false                     ,
        chance    =  1                        ,
        interval  =  3                        ,

        action    = function (pos, node)
            if eregions:has_feature (pos, "lavagel") then
                local newnode

                if node.name == "default:lava_source" then
                    newnode = "default:lava_gel"
                else
                    newnode = "air"
                end

                minetest.set_node (pos, { name = newnode })
            end
        end
    })
end
eregions.addabm_map ["lavagel"] = eregions_addabm_lavagel

-- ===================================================================

function eregions:add (efeature, pos1, pos2)

    local id = findFirstUnusedIndex (self.eregions)
    self.eregions [id] = {
        pos1     = pos1     ,
        pos2     = pos2     ,
        efeature = efeature ,
    }

    if self.store then
        local sid = self.store:insert_area (pos1, pos2,
            tostring (id))
        if self:checkAreaStoreId (sid) then
            self.store_ids [id] = sid
        end
    end

    eregions_addabm (efeature)
    return id
end

-- ===================================================================

function eregions:remove (id)
    if self.eregions [id] == nil then return false end

    -- Remove main entry
    self.eregions [id] = nil

    -- Remove from AreaStore
    if  self.store then
        self.store:remove_area (self.store_ids [id])
        self.store_ids [id] = nil
    end

    return true
end

-- ===================================================================
-- Move an eregion

function eregions:move (id, eregion, pos1, pos2)
    eregion.pos1 = pos1
    eregion.pos2 = pos2

    if self.store then
        self.store:remove_area (eregions.store_ids [id])
        local sid = self.store:insert_area (pos1, pos2, tostring (id))
        if self:checkAreaStoreId (sid) then
            self.store_ids[id] = sid
        end
    end
end

-- ===================================================================

function eregions:isERegionEFeature(id, name)
    local cur = self.eregions[id]
    if cur and minetest.check_player_privs(name, self.adminPrivs) then
        return true
    end
    while cur do
        if cur.efeature == name then
            return true
        elseif cur.parent then
            cur = self.eregions[cur.parent]
        else
            return false
        end
    end
    return false
end

-- ===================================================================
-- End of module.