feat: fix naming

lua/cp/problem.lua

@@ -0,0 +1,37 @@
+---@class ProblemContext
+---@field contest string Contest name (e.g. "atcoder", "codeforces")
+---@field problem_id string Raw problem ID (e.g. "abc123", "1933")
+---@field problem_letter? string Problem letter for AtCoder/Codeforces (e.g. "a", "b")
+---@field source_file string Source filename (e.g. "abc123a.cpp")
+---@field binary_file string Binary output path (e.g. "build/abc123a")
+---@field input_file string Input test file path (e.g. "io/abc123a.in")
+---@field output_file string Output file path (e.g. "io/abc123a.out")
+---@field expected_file string Expected output path (e.g. "io/abc123a.expected")
+---@field problem_name string Canonical problem identifier (e.g. "abc123a")
+
+local M = {}
+
+---@param contest string
+---@param problem_id string
+---@param problem_letter? string
+---@param config cp.Config
+---@return ProblemContext
+function M.create_context(contest, problem_id, problem_letter, config)
+	local filename_fn = config.filename or require("cp.config").default_filename
+	local source_file = filename_fn(contest, problem_id, problem_letter)
+	local base_name = vim.fn.fnamemodify(source_file, ":t:r")
+
+	return {
+		contest = contest,
+		problem_id = problem_id,
+		problem_letter = problem_letter,
+		source_file = source_file,
+		binary_file = ("build/%s"):format(base_name),
+		input_file = ("io/%s.in"):format(base_name),
+		output_file = ("io/%s.out"):format(base_name),
+		expected_file = ("io/%s.expected"):format(base_name),
+		problem_name = base_name,
+	}
+end
+
+return M