local sign = {}

local sha256 = require("sha256")

function sign.sign(key, secret, time, host, path, headers, contentSha256, region)
        local day = os.date("%Y%m%d", time)
        local date = os.date("%a, %d %b %Y %H:%M:%S GMT", time)
        local timestamp = os.date("%Y%m%dT%H%M%SZ", time)
        local dateKey = sha256.hmac_sha256("AWS4" .. secret, day)
        local dateRegionKey = sha256.hmac_sha256(dateKey, region)
        local dateRegionSvcKey = sha256.hmac_sha256(dateRegionKey, 's3')
        local signingKey = sha256.hmac_sha256(dateRegionSvcKey, 'aws4_request')
        print("DateKey:          " .. dateKey)
        print("DateRegionKey:    " .. dateRegionKey)
        print("DateRegionSvcKey: " .. dateRegionSvcKey)
        print("SigningKey:       " .. signingKey)

        headers["x-amz-content-sha256"] = contentSha256
        headers["date"] = date
        headers["host"] = host

        local keys = {}
        for k in pairs(headers) do
                table.insert(keys, k)
        end
        table.sort(keys)

        local signedHeaders = ""

        local request = "PUT\n" .. path .. "\n"
        for _, k in ipairs(keys) do
                request = request .. "\n" .. k .. ":" .. headers[k]
                signedHeaders = signedHeaders .. ";" .. k
        end
        signedHeaders = string.sub(signedHeaders, 2)

        request = request .. "\n\n" .. signedHeaders .. "\n" .. contentSha256
        print("Request:\n" .. request)
        print("-------")
        local stringToSign = "AWS4-HMAC-SHA256\n" .. timestamp  .. "\n" .. day .. "/" .. region .. "/s3/aws4_request\n" .. sha256.sha256(request)
        print("String to sign:\n" .. stringToSign)
        print("-------")
        local signature = sha256.hmac_sha256(signingKey, stringToSign)
        print("Signature:\n" .. signature)
        print("-------")

        local result = "AWS4-HMAC-SHA256 Credential=" .. key .. "/" .. day .. "/" .. region .. "/s3/aws4_request,SignedHeaders=" .. signedHeaders
        result = result .. ",Signature=" .. signature
        return result
end

return sign