-- ffi/libc.lua — shared libc bindings: chdir, errno, strerror.
-- Phase 0: just enough to make `cd` interception work in executor.lua.
-- See docs/PHASE0.md §7.

local ffi = require("ffi")

ffi.cdef[[
int   chdir(const char *path);
int  *__errno_location(void);
char *strerror(int errnum);
]]

local C = ffi.C

local M = {}

-- Apply chdir per PHASE0.md §7 (intercepts `cd` so wd persists across popen).
-- Returns: true on success; false, errmsg on failure.
function M.chdir(path)
    local rc = C.chdir(path)
    if rc == 0 then return true end
    return false, ffi.string(C.strerror(C.__errno_location()[0]))
end

function M.errno()
    return C.__errno_location()[0]
end

function M.strerror(en)
    return ffi.string(C.strerror(en))
end

return M