-- Mock implementation of resty.sha256 for testing
-- Uses system sha256sum command since we don't have OpenResty libraries

local sha256 = {}
sha256.__index = sha256

function sha256:new()
    local obj = {
        buffer = ""
    }
    setmetatable(obj, sha256)
    return obj
end

function sha256:update(data)
    self.buffer = self.buffer .. data
end

function sha256:final()
    -- Use sha256sum command to compute hash
    local handle = io.popen("echo -n '" .. self.buffer:gsub("'", "'\\''") .. "' | sha256sum")
    local result = handle:read("*a")
    handle:close()

    -- Parse hex string into binary
    local hex = result:match("^(%x+)")
    local binary = {}
    for i = 1, #hex, 2 do
        table.insert(binary, string.char(tonumber(hex:sub(i, i+1), 16)))
    end

    return table.concat(binary)
end

return sha256