local ZK = {}

local ls = require 'zettelkasten.list'

function ZK.init(vimapi)
    vim = vimapi or vim
    ZK.options = {
        anchor_separator = vim.g["zettel_anchor_separator"] or
            vim.b["zettel_anchor_separator"] or "_",
        zettel_extension = vim.g["zettel_extension"] or
            vim.b["zettel_extension"] or ".md"
        -- zettel_root = vim.g["zettel_root"] or vim.b["zettel_root"] or "~/documents/notes",
        -- TODO zettel_anchor_pattern = regex? -> needs custom creation function in `create_anchor`
    }
end

-- entrypoint for pressing the zettel key when the cursor
-- is either on an existing link  (it will then
-- follow it) or over text (it will then turn it into a
-- zettel link)
function ZK.follow_link()
    assert(false, "NOT IMPLEMENTED")
    return ''
end

-- Return a valid zettelkasten anchor,
-- composed of yymmddHHMM.
--
-- date can be passed in as a table containing a year, a month, a day, an hour,
-- and a minute key. Returns nil if the date passed in is invalid.
-- If no date is passed in, returns Zettel anchor for current moment.
function ZK.create_anchor(date)
    local timestamp
    if pcall(function() timestamp = os.time(date) end) then
        return os.date('%y%m%d%H%M', timestamp)
    else
        return nil
    end
end

-- Returns a link to a markdown file with the date replaced with a zettel anchor,
-- and the text cleaned up to be useful in a link.
function ZK.create_link(text, date)
    text = text or ""
    local o = ZK.options
    if text == "" then
        text = "" .. ZK.create_anchor(date)
    else
        text = text:lower():gsub(" ", "-")
        text = "" .. ZK.create_anchor(date) .. (o.anchor_separator or "_") ..
                   text
    end
    return text .. (o.zettel_extension or ".md")
end

-- Returns all zettel in path as a
-- { "anchor" = "path/to/zettel/anchor filename.md" }
-- table.
-- Recurses into subdirectories if recursive argument is true.
function ZK.get_zettel_list(path, recursive)
    return ls.get_anchors_and_paths(path, recursive or false)
end

return {
    init = ZK.init,
    zettel_link_create = ZK.zettel_link_create,
    create_anchor = ZK.create_anchor,
    create_link = ZK.create_link,
    get_zettel_list = ZK.get_zettel_list
}