-- 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 testify = testimony.new("== mneme: cursor iteration ==")

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

testify:that("cursor iterates all keys in sorted order", function()
	local path = tmp_path()
	local db = mneme.open(path, { sync = "none" })
	local txn = db:txn_begin(false)
	local root = db:info().keyspace_root_pgno

	-- Insert 50 keys in random-ish order
	local keys = {}
	for i = 1, 50 do
		local k = string.format("key:%04d", (i * 37) % 50 + 1)
		root = txn:btree_put(root, k, "v" .. i)
		keys[k] = true
	end

	-- Iterate with cursor
	local cur = txn:cursor_open(root)
	local collected = {}
	local k = cur:first()
	while k do
		table.insert(collected, k)
		k = cur:next()
	end
	cur:close()

	-- Should be sorted
	testimony.assert_equal(50, #collected)
	for i = 2, #collected do
		testimony.assert_true(collected[i - 1] < collected[i])
	end

	txn:abort()
	db:close()
	std.fs.remove(path)
end)

testify:that("cursor iterates backward with last/prev", function()
	local path = tmp_path()
	local db = mneme.open(path, { sync = "none" })
	local txn = db:txn_begin(false)
	local root = db:info().keyspace_root_pgno

	for i = 1, 20 do
		root = txn:btree_put(root, string.format("r:%03d", i), "v")
	end

	local cur = txn:cursor_open(root)
	local collected = {}
	local k = cur:last()
	while k do
		table.insert(collected, k)
		k = cur:prev()
	end
	cur:close()

	testimony.assert_equal(20, #collected)
	-- Should be reverse sorted
	for i = 2, #collected do
		testimony.assert_true(collected[i - 1] > collected[i])
	end

	txn:abort()
	db:close()
	std.fs.remove(path)
end)

testify:that("cursor seek positions at first key >= target", function()
	local path = tmp_path()
	local db = mneme.open(path, { sync = "none" })
	local txn = db:txn_begin(false)
	local root = db:info().keyspace_root_pgno

	for i = 1, 10 do
		root = txn:btree_put(root, string.format("s:%02d", i * 2), "v")
	end
	-- Keys: s:02, s:04, s:06, s:08, s:10, s:12, s:14, s:16, s:18, s:20

	local cur = txn:cursor_open(root)

	-- Seek to "s:05" → should land on "s:06"
	local k = cur:seek("s:05")
	testimony.assert_equal("s:06", k)

	-- Seek to "s:10" → exact match
	k = cur:seek("s:10")
	testimony.assert_equal("s:10", k)

	-- Seek to "s:21" → past all keys → nil
	k = cur:seek("s:21")
	testimony.assert_nil(k)

	-- Seek to "s:01" → should land on "s:02" (first key)
	k = cur:seek("s:01")
	testimony.assert_equal("s:02", k)

	cur:close()
	txn:abort()
	db:close()
	std.fs.remove(path)
end)

testify:that("cursor skips long runs of emptied leaves", function()
	local path = tmp_path()
	local db = mneme.open(path, { sync = "none" })

	local txn = db:txn_begin(false)
	local root = db:info().keyspace_root_pgno
	local big = string.rep("v", 600)
	for i = 1, 1200 do
		root = txn:btree_put(root, string.format("e:%06d", i), big)
	end
	for i = 2, 1199 do
		root = txn:btree_del(root, string.format("e:%06d", i))
	end
	local ok, err = txn:commit()
	testimony.assert_true(ok, err)

	txn = db:txn_begin(true)
	local cur = txn:cursor_open(root)

	local k = cur:first()
	testimony.assert_equal("e:000001", k)
	k = cur:next()
	testimony.assert_equal("e:001200", k)
	testimony.assert_nil(cur:next())

	k = cur:last()
	testimony.assert_equal("e:001200", k)
	k = cur:prev()
	testimony.assert_equal("e:000001", k)
	testimony.assert_nil(cur:prev())

	k = cur:seek("e:000500")
	testimony.assert_equal("e:001200", k)

	cur:close()
	txn:abort()
	db:close()
	std.fs.remove(path)
end)

testify:that("cursor on empty tree returns nil", function()
	local path = tmp_path()
	local db = mneme.open(path, { sync = "none" })
	local txn = db:txn_begin(true)
	local root = db:info().keyspace_root_pgno

	local cur = txn:cursor_open(root)
	local k = cur:first()
	testimony.assert_nil(k)

	k = cur:last()
	testimony.assert_nil(k)

	cur:close()
	txn:abort()
	db:close()
	std.fs.remove(path)
end)

testify:that("cursor works across leaf splits (many keys)", function()
	local path = tmp_path()
	local db = mneme.open(path, { sync = "none" })
	local txn = db:txn_begin(false)
	local root = db:info().keyspace_root_pgno

	-- Insert 300 keys to force multiple leaf pages
	for i = 1, 300 do
		root = txn:btree_put(root, string.format("m:%06d", i), "v" .. i)
	end

	local cur = txn:cursor_open(root)
	local count = 0
	local prev_k = ""
	local k, v = cur:first()
	while k do
		count = count + 1
		testimony.assert_true(k > prev_k)
		prev_k = k
		k, v = cur:next()
	end
	cur:close()

	testimony.assert_equal(300, count)

	txn:abort()
	db:close()
	std.fs.remove(path)
end)

testify:conclude()