--[[

A package of utilities related to the Extension and its interaction
with the server.

]]--

local ExtUtils = {}
local cjson = require "cjson"

function ExtUtils.slurpFile( name )
    local f = assert( io.open( name, "rb" ) )
    local content = f:read( "*all" )
    f:close()
    return content
end

function ExtUtils.writeFile( name, content )
    local f = assert( io.open( name, "w" ) )
    local content = f:write( content )
    f:close()
end

--[[

When an Extension is installed, the bundle is unpackaged and put
in a directory under 'server.extensions.dir'.  The GetArchDirFileName()
function returns a path to a file in that directory.

The Extension manifest is a JSON file with various bits of useful
metadata that an Extension often needs, so this function gets it
ready to use.

]]--

function getManifest()
  local fn = Helix.Core.Server.GetArchDirFileName( "manifest.json" )
  return cjson.decode( ExtUtils.slurpFile( fn ) )
end

-- Remove leading and trailing whitespace from a string.

function trim( s )
   return ( s:gsub( "^%s*(.-)%s*$", "%1" ) )
end

--[[

Extensions have a single global configuration and one for each instance
of the Extension.  The GetInstanceConfigData() function returns a dictionary
of the k/v pairs that are saved in the instance config that caused the
Extension to be running.  Examples of what might be in an instance config
are the depot paths the Extension is activated for, or a list of users
who the Extension is used on.

]]--

function getICfg()
  local cfg = {}
  for k, v in pairs( Helix.Core.Server.GetInstanceConfigData() ) do
    -- It's the Extension's responsibility to massage the data
    -- into the format it expects.  Here, we make sure that there's
    -- no empty answers and that the whitespace has been trimmed off.
    if string.len( v ) > 0 then
      cfg[ k ] = trim( v )
    end
  end
  cfg[ "ngroups" ] = 0
  if cfg[ "groups" ] ~= nil then
    local groups = {}
    local n = 0
    -- Create a table of groups whose members we target.
    for g in string.gmatch( cfg[ "groups" ], "%S+" ) do
      groups[ g ] = 1
      n = n + 1
    end
    cfg[  "groups" ] = groups
    cfg[ "ngroups" ] = n
  end
  return cfg
end

-- Return a string we can use to identify the Extension.
function ExtUtils.getID()
  return ExtUtils.manifest[ "name" ] .. "/" .. ExtUtils.manifest[ "key" ] .. "/" ..
         ExtUtils.manifest[ "version_name" ]
end

function ExtUtils.msgHeader()
  return ExtUtils.getID() .. ":  "
end

ExtUtils.manifest = {}
ExtUtils.iCfgData = {}

--[[

An Extension is loaded and can be executed multiple times on a
single client connection, so in order to minimize the amount of work
it does, we only initialize ourselves once at the beginning (read
the manifest, etc).

]]--

function ExtUtils.init()
  if ExtUtils.iCfgData[ "specName" ] == nil then
    ExtUtils.iCfgData = getICfg()
-- todo: split the user list into another table
  end
  if ExtUtils.manifest[ "key" ] == nil then
    ExtUtils.manifest = getManifest()
  end
end

return ExtUtils