-- mini.diff source backed by jj.

local M = {}

local function resolve(buf_id)
	local name = vim.api.nvim_buf_get_name(buf_id)
	if name == "" then
		return nil
	end

	local change_id, rel = name:match("^jj://([^/]+)/(.+)$")
	if change_id then
		-- The path in the uri is repo-relative; jj resolves it from anywhere in
		-- the repo, so run from the current working directory.
		return { rev = change_id .. "-", file = rel, cwd = vim.fn.getcwd() }
	end

	local path = vim.uv.fs_realpath(name)
	if path == nil then
		return nil
	end
	return { rev = "@-", file = path, cwd = vim.fs.dirname(path) }
end

local function set_ref_text(buf_id)
	if not vim.api.nvim_buf_is_valid(buf_id) then
		return
	end
	local target = resolve(buf_id)
	if target == nil then
		return
	end
	vim.system(
		{ "jj", "file", "show", "--ignore-working-copy", "-r", target.rev, target.file },
		{ cwd = target.cwd, text = true },
		vim.schedule_wrap(function(obj)
			if not vim.api.nvim_buf_is_valid(buf_id) then
				return
			end
			local text = obj.code == 0 and obj.stdout or ""
			pcall(MiniDiff.set_ref_text, buf_id, text)
		end)
	)
end

local function group_name(buf_id)
	return "MiniDiffSourceJj" .. buf_id
end

local function attach(buf_id)
	local target = resolve(buf_id)
	if target == nil then
		return false
	end

	if vim.fs.root(target.cwd, ".jj") == nil then
		return false
	end

	local group = vim.api.nvim_create_augroup(group_name(buf_id), { clear = true })
	vim.api.nvim_create_autocmd({ "BufWritePost", "BufReadPost", "BufEnter", "FocusGained", "FileChangedShellPost" }, {
		group = group,
		buffer = buf_id,
		desc = "Refresh jj diff reference",
		callback = function()
			set_ref_text(buf_id)
		end,
	})

	set_ref_text(buf_id)
end

local function detach(buf_id)
	pcall(vim.api.nvim_del_augroup_by_name, group_name(buf_id))
end

M.source = {
	name = "jj",
	attach = attach,
	detach = detach,
}

-- support jj:// buffers
function M.setup()
	local group = vim.api.nvim_create_augroup("MiniDiffJjRevisionBuffers", { clear = true })
	vim.api.nvim_create_autocmd({ "BufWinEnter", "BufReadPost" }, {
		group = group,
		desc = "Enable mini.diff on jj revision buffers",
		callback = function(ev)
			vim.schedule(function()
				if not vim.api.nvim_buf_is_valid(ev.buf) then
					return
				end
				if vim.api.nvim_buf_get_name(ev.buf):match("^jj://") then
					pcall(require("mini.diff").enable, ev.buf)
				end
			end)
		end,
	})
end

return M