local datafile = require "datafile"
local dir = require "pl.dir"
local path = require "pl.path"
local store = require "volksdata.store"

local term = require "volksdata.term"
local nsm = require "volksdata.namespace"


-- Read only module properties.
local PROTECTED = {
    store = true,
    reset_store = true,
}


local config_path = os.getenv("PKAR_CONFIG_DIR") or
        path.dirname(datafile.path("config/app.lua"))

print ("Using config at:", config_path)

local config = dofile(path.join(config_path, "app.lua"))
local store_id = "file://" .. (os.getenv("PKAR_BASE") or config.fs.dres_path)

-- Fill namespace map from config.
for pfx, ns in pairs(config.namespace) do nsm.add(pfx, ns) end


local M = {
    -- Project root path.
    config_path = config_path,
    config = config,

    store_id = store_id,

    --Logger config.
    logger = require "sllog":init{
      {"err",   "%T PKAR %-5L ",          "%n", io.stderr},
      {"warn",  "%T PKAR %-5L ",          "%n", io.stderr},
      {"info",  "%T PKAR %-5L ",          "%n", io.stderr},
      {"debug", "%T PKAR %-5L%f (%S) ",   "%n", io.stderr},
      timefn=(require "socket" or {}).gettime,
      report="debug",
      hookrequire=false,
      level="debug",
    },

    -- Commonly used terms.
    RDF_TYPE = term.new_iriref(term.RDF_TYPE),

    -- Methods.

    -- Escape strings for use in gsub patterns.
    escape_ptn = function(src)
        return src:gsub("[%(%)%.%%%+%-%*%?%[%]%^%$]", "%%%0")
    end,

}


--[[
  Generate pairtree directory and file path from an ID string and prefix.

  The directory is created if not existing.

  The ID string can include the `par:` namespace prefix or the fully qualified
  namespace.

  ext is optional, and is appended to the raw path.

  if no_create is not nil or false, the directory will not be checked for
  existence or created. This is normally set for web paths.

  return: full file path, with the optional extension if provided.
--]]
M.gen_pairtree = function (pfx, id_str, ext, no_create)
    local bare_id = id_str:gsub(nsm.get_ns("par"), ""):gsub("^par:", "")
    local res_dir = path.join(pfx, bare_id:sub(1,2), bare_id:sub(3,4))

    local created, err
    if (path.isdir(res_dir)) or no_create then created = false
    else
        created, err = dir.makepath(res_dir)
        if not created then error(err) end
    end

    local fpath
    if (res_dir) then fpath = path.join(res_dir, bare_id .. (ext or "")) end

    return fpath, created
end


-- No more assignments to the module afte here.


local mt = {
    __index = function(t, k)
        if (k == "store") then
            if not rawget(t, "_store") then
                    rawset(t, "_store", store.new(store.MDB, store_id)) end
            return rawget(t, "_store")

        -- WIPE ALL DATA from the store and returns the new empty store handle.
        elseif (k == "reset_store") then
            rawset(t, "_store", store.new(store.MDB, store_id, true))
            return rawget(t, "_store")
        end
    end,

    __newindex = function () return nil, "Module is read only." end
}

setmetatable (M, mt)

math.randomseed(M.config.id.seed or os.time())

return M