local json = require('opus.json')
local Util = require('opus.util')

local GITHUB_TREE_URL = 'https://api.github.com/repos/%s/%s/git/trees/%s?recursive=1'
local GITHUB_FILE_URL = 'https://raw.githubusercontent.com/%s/%s/%s/%s'
local GITEA_TREE_URL  = 'https://%s/api/v1/repos/%s/%s/git/trees/%s?recursive=1'
local GITEA_FILE_URL  = 'https://%s/%s/%s/raw/branch/%s/%s'
local TREE_HEADERS = {}
local git = { }

if _G._GIT_API_KEY then
	TREE_HEADERS.Authorization = 'token ' .. _G._GIT_API_KEY
end

local function parseTree(data, path, fileUrlFn)
	if data.message then
		if data.message:find("API rate limit exceeded") then
			error("Out of API calls, try again later")
		end
		if data.message == "Not found" or data.message == "Not Found" then
			error("Invalid repository")
		end
	end

	local list = { }
	for _, v in pairs(data.tree) do
		if v.type == "blob" then
			v.path = v.path:gsub("%s", "%%20")
			if not path then
				list[v.path] = {
					url = fileUrlFn(v.path),
					size = v.size,
				}
			elseif Util.startsWith(v.path, path) then
				local p = string.sub(v.path, #path)
				list[p] = {
					url = fileUrlFn(path .. p),
					size = v.size,
				}
			end
		end
	end
	return list
end

local function fetchTree(url)
	local contents, msg = Util.httpGet(url, TREE_HEADERS)
	if not contents then
		error(string.format('Failed to download %s\n%s', url, msg), 2)
	end
	return json.decode(contents) or error('Invalid repository')
end

-- GitHub: user/repo/branch/subdir/
local function listGithub(repository)
	local t = Util.split(repository, '(.-)/')
	local user   = table.remove(t, 1)
	local repo   = table.remove(t, 1)
	local branch = table.remove(t, 1) or 'main'
	local path   = not Util.empty(t) and (table.concat(t, '/') .. '/') or nil

	local data = fetchTree(string.format(GITHUB_TREE_URL, user, repo, branch))
	return parseTree(data, path, function(p)
		return string.format(GITHUB_FILE_URL, user, repo, branch, p)
	end)
end

-- Gitea: gitea://host/user/repo/branch/subdir/
local function listGitea(host, remainder)
	local t = Util.split(remainder, '(.-)/')
	local user   = table.remove(t, 1)
	local repo   = table.remove(t, 1)
	local branch = table.remove(t, 1) or 'main'
	local path   = not Util.empty(t) and (table.concat(t, '/') .. '/') or nil

	local data = fetchTree(string.format(GITEA_TREE_URL, host, user, repo, branch))
	return parseTree(data, path, function(p)
		return string.format(GITEA_FILE_URL, host, user, repo, branch, p)
	end)
end

function git.list(repository)
	local host_type, host, rest = repository:match('^(%w+)://(.-)/(.*)')
	if host_type == 'gitea' then
		return listGitea(host, rest)
	end
	return listGithub(repository)
end

return git