{ lib, machineDir, ... }: let allMachineNames = lib.mapAttrsToList (name: _: name) (builtins.readDir machineDir); getFactPath = fact: machine: "${machineDir}/${machine}/facts/${fact}"; readFact = fact: machine: let path = getFactPath fact machine; in if builtins.pathExists path then builtins.readFile path else null; # Example: # # readFactFromAllMachines zerotier-ip # => { # machineA = "1.2.3.4"; # machineB = "5.6.7.8"; # }; readFactFromAllMachines = fact: let machines = allMachineNames; facts = lib.genAttrs machines (readFact fact); filteredFacts = lib.filterAttrs (_machine: fact: fact != null) facts; in filteredFacts; # all given facts are are set and factvalues are never null. # # Example: # # readFactsFromAllMachines [ "zerotier-ip" "syncthing.pub" ] # => { # machineA = # { # "zerotier-ip" = "1.2.3.4"; # "synching.pub" = "1234"; # }; # machineB = # { # "zerotier-ip" = "5.6.7.8"; # "synching.pub" = "23456719"; # }; # }; readFactsFromAllMachines = facts: let # machine -> fact -> factvalue machinesFactsAttrs = lib.genAttrs allMachineNames (machine: lib.genAttrs facts (fact: readFact fact machine)); # remove all machines which don't have all facts set filteredMachineFactAttrs = lib.filterAttrs (_machine: values: builtins.all (fact: values.${fact} != null) facts) machinesFactsAttrs; in filteredMachineFactAttrs; in { inherit allMachineNames getFactPath readFact readFactFromAllMachines readFactsFromAllMachines; }