local dates = require "activity.dates"
local git = {}


function git.log (dirname, entries, filter)
	entries = entries or {}
	if not dirname then
		error "did not provide repo"
	end
	local handle = io.popen(([[git -C %s log --all --format="%%aE;%%cE;%%as"]]):format(dirname))
	for line in handle:lines() do
		local author, committer, year, month, day = line:match"([^;]*);([^;]*);(%d+)%-(%d+)%-(%d+)"
		local date = {year=tonumber(year), month=tonumber(month), day=tonumber(day)}
		local entry = {author=author, committer=committer, date=date}
		if not filter or filter(entry) then
			table.insert(entries, entry)
		end
	end
	local ok, _ = handle:close()
	if not ok then
		io.stderr:write("could not read repo: ", dirname, "\n")
	end
	return not ok, entries
end


function git.lookup (repositories, filter)
	local lookup = {}
	local errors = nil
	local entries = {}
	for _, dirname in pairs(repositories) do
		local err, _ = git.log(dirname, entries, filter)
		errors = errors or err
	end
	for _, entry in pairs(entries) do
		local day = dates.day_of_year(entry.date)
		local year = entry.date.year
		lookup[year] = lookup[year] or {}
		lookup[year][day] = (lookup[year][day] or 0) + 1
	end
	return errors, function (year, day)
		return (lookup[year] or {})[day] or 0
	end
end


function git.maybe_filter (field, set)
	if next(set) then
		return function (entry)
			return set[entry[field]]
		end
	end
	return nil
end


return git