--[[

This file defines a few helper functions, in particular with respect to pandoc.

--]]

local Options = require("acronyms_options")


local Helpers = {}


-- Helper function to determine pandoc's version.
-- `version` must be a table of numbers, e.g., `{2, 17, 0, 1}`
function Helpers.isAtLeastVersion(version)
    -- `PANDOC_VERSION` exists since 2.1, but we never know...
    if PANDOC_VERSION == nil then
        return false
    end
    -- Loop up over the components
    -- e.g., `2.17.0.1` => [0]=2, [1]=17, [2]=0, [3]=1
    for k, v in ipairs(version) do
        if PANDOC_VERSION[k] == nil or PANDOC_VERSION[k] < version[k] then
            -- Examples: 2.17 < 2.17.0.1, or 2.16 < 2.17
            return false
        elseif PANDOC_VERSION[k] > version[k] then
            -- Example: 2.17 > 2.16.2 (we do not need to check the next!)
            return true
        end
    end
    -- At this point, all components are equal
    return true
end


-- Helper function to determine whether a metadata field is a list.
function Helpers.isMetaList(field)
    -- We want to know whether we have multiple values (MetaList).
    -- Pandoc 2.17 introduced a compatibility-breaking change for this:
    --  the `.tag` is no longer present in >= 2.17 ;
    --  the `pandoc.utils.type` function is only available in >= 2.17
    if Helpers.isAtLeastVersion({2, 17}) then
        -- Use the new `pandoc.utils.type` function
        return pandoc.utils.type(field) == "List"
    else
        -- Use the (old) `.tag` type attribute
        return field.t == "MetaList"
    end
end


-- Helper function to generate the ID (identifier) from an acronym key.
-- The ID can be used for, e.g., links.
function Helpers.key_to_id(key)
    return Options["id_prefix"] .. key
end


-- Similar helper but for the link itself (based on the ID).
function Helpers.key_to_link(key)
    return "#" .. Helpers.key_to_id(key)
end


return Helpers