local string = string
local table = table
local io = io

local lyaml = require("lyaml")


local M = {}

-- Parameters that do not get inherited.
local NO_INHERIT = {abstract = true}
local MODEL_PATH = "./config/model/"


local function camel2snake(src)
    return string.lower(
        string.gsub(
            string.gsub (src, "^pas:", ""),  -- Strip namespace.
            "([^^])(%u)", "%1_%2"  -- Uppercase (except initial) to underscore.
        )
    )
end


M.parse_model = function(mod_id)
    local hierarchy = {}

    local function traverse(mod_id)
        print("traversing:", mod_id)
        local fname = camel2snake (mod_id)
        local fh = assert(io.open(MODEL_PATH .. fname .. ".yml"), "r")
        local yml_data = fh:read("a")
        fh:close()
        local model = lyaml.load(yml_data)
        model.id = mod_id
        --print("Model: ")
        --for k, v in pairs(model) do print (k, v) end

        -- Prepend to hierarchy.
        table.insert(hierarchy, 1, model)

        if model.broader then traverse(model.broader) end
    end
    traverse(mod_id)

    local lineage = {}  -- Config ID lineage, from ancestor to leaf.
    for _, mod in ipairs(hierarchy) do table.insert(lineage, mod.id) end
    --[[
    for k, v in ipairs(hierarchy) do 
        for kk, vv in pairs(v) do print(k, kk, vv) end
    end
    --]]

    local function merge(src, dest)
        for k, v in pairs(src) do
            if NO_INHERIT[k] then goto continue end
            if type(v) == "table" then
                dest[k] = dest[k] or {}
                assert(type(dest[k]) == "table")
                merge(v, dest[k])
            else
                dest[k] = v
            end
            ::continue::
        end
    end
    local config = {}

    for _, src_config in ipairs(hierarchy) do
        merge(src_config, config)
    end

    return config
end

return M