-- SPDX-FileCopyrightText: © 2026 Vladimir Zorin <vladimir@deviant.guru>
-- SPDX-License-Identifier: OWL-1.0 or later

local testimony = require("testimony")
local std = require("std")
local mneme = require("mneme")
local core = require("mneme.core")

local testify = testimony.new("== mneme: reader registry ==")

local tmp_path = function()
	return "/tmp/mneme_readers_" .. std.nanoid() .. ".mneme"
end

local function teardown(db, path)
	db:close()
	std.fs.remove(path)
end

testify:that("same-handle read txn keeps its snapshot root after writer commit", function()
	local path = tmp_path()
	local db = mneme.open(path, { sync = "none" })
	local ks = db:keyspace("t")
	ks:set("k", "v1")

	local reader = db:txn_begin(true)
	local snap_root = reader:meta().keyspace_root_pgno
	local before_pg = reader:btree_get(snap_root, "t")
	testimony.assert_not_nil(before_pg)
	local before_root = core.unpack_u32(before_pg)
	testimony.assert_equal("v1", reader:btree_get(before_root, "k"))

	ks:set("k", "v2")

	local still_pg = reader:btree_get(snap_root, "t")
	testimony.assert_not_nil(still_pg)
	local still_root = core.unpack_u32(still_pg)
	testimony.assert_equal(before_root, still_root)
	testimony.assert_equal("v1", reader:btree_get(still_root, "k"))

	reader:abort()
	teardown(db, path)
end)

testify:that("cross-handle read txn keeps its snapshot root after writer commit", function()
	local path = tmp_path()
	local db_a = mneme.open(path, { sync = "none" })
	local db_b = mneme.open(path, { sync = "none" })

	db_a:keyspace("t"):set("k", "one")

	local reader = db_a:txn_begin(true)
	local snap_root = reader:meta().keyspace_root_pgno
	local before_pg = reader:btree_get(snap_root, "t")
	testimony.assert_not_nil(before_pg)
	local before_root = core.unpack_u32(before_pg)
	testimony.assert_equal("one", reader:btree_get(before_root, "k"))

	db_b:keyspace("t"):set("k", "two")

	local still_pg = reader:btree_get(snap_root, "t")
	testimony.assert_not_nil(still_pg)
	local still_root = core.unpack_u32(still_pg)
	testimony.assert_equal(before_root, still_root)
	testimony.assert_equal("one", reader:btree_get(still_root, "k"))
	testimony.assert_equal("two", db_b:keyspace("t"):get("k"))

	reader:abort()
	db_b:close()
	teardown(db_a, path)
end)

testify:conclude()