include /etc/nginx/conf.d/include/proxy-buffer;
include /etc/nginx/conf.d/include/proxy-pass-internal;
include /etc/nginx/conf.d/include/portal-access-check;

# variable definititions - we need to define a variable to be able to access it in lua by ngx.var.something
set $skylink ''; # placeholder for the base64 skylink
set $skylink_base32 ''; # placeholder for the base32 skylink

# resolve handshake domain by requesting to /hnsres endpoint and assign correct values to $skylink and $rest
rewrite_by_lua_block {
    local json = require('cjson')
    local httpc = require("resty.http").new()

    -- make a get request to /hnsres endpoint with the domain name from request_uri
    -- 10.10.10.50 points to handshake-api service (alias not available when using resty-http)
    local hnsres_res, hnsres_err = httpc:request_uri("http://10.10.10.50:3100/hnsres/" .. ngx.var.hns_domain)

    -- print error and exit with 500 or exit with response if status is not 200
    if hnsres_err or (hnsres_res and hnsres_res.status ~= ngx.HTTP_OK) then
        ngx.status = (hnsres_err and ngx.HTTP_INTERNAL_SERVER_ERROR) or hnsres_res.status
        ngx.header["content-type"] = "text/plain"
        ngx.say(hnsres_err or hnsres_res.body)
        return ngx.exit(ngx.status)
    end

    -- since /hnsres endpoint response is a json, we need to decode it before we access it
    -- example response: '{"skylink":"sia://XABvi7JtJbQSMAcDwnUnmp2FKDPjg8_tTTFP4BwMSxVdEg"}'
    local hnsres_json = json.decode(hnsres_res.body)

    -- define local variable containing rest of the skylink if provided
    local skylink_rest

    if hnsres_json.skylink then
        -- try to match the skylink with sia:// prefix
        skylink, skylink_rest = string.match(hnsres_json.skylink, "sia://([^/?]+)(.*)")

        -- in case the skylink did not match, assume that there is no sia:// prefix and try to match again
        if skylink == nil then
            skylink, skylink_rest = string.match(hnsres_json.skylink, "/?([^/?]+)(.*)")
        end
    elseif hnsres_json.registry then
        local publickey = hnsres_json.registry.publickey
        local datakey = hnsres_json.registry.datakey

        -- make a get request to /skynet/registry endpoint with the credentials from text record
        -- 10.10.10.10 points to sia service (alias not available when using resty-http)
        local registry_res, registry_err = httpc:request_uri("http://10.10.10.10:9980/skynet/registry?publickey=" .. publickey .. "&datakey=" .. datakey, {
            headers = { ["User-Agent"] = "Sia-Agent" }
        })

        -- print error and exit with 500 or exit with response if status is not 200
        if registry_err or (registry_res and registry_res.status ~= ngx.HTTP_OK) then
            ngx.status = (registry_err and ngx.HTTP_INTERNAL_SERVER_ERROR) or registry_res.status
            ngx.header["content-type"] = "text/plain"
            ngx.say(registry_err or registry_res.body)
            return ngx.exit(ngx.status)
        end

        -- since /skynet/registry endpoint response is a json, we need to decode it before we access it
        local registry_json = json.decode(registry_res.body)
        -- response will contain a hex encoded skylink, we need to decode it
        local data = (registry_json.data:gsub('..', function (cc)
            return string.char(tonumber(cc, 16))
        end))

        skylink = data
    end

    -- fail with a generic 404 if skylink has not been extracted from a valid /hnsres response for some reason
    if not skylink then
        return ngx.exit(ngx.HTTP_NOT_FOUND)
    end

    ngx.var.skylink = skylink
    if ngx.var.path == "/" and skylink_rest ~= nil and skylink_rest ~= "" and skylink_rest ~= "/" then
        ngx.var.path = skylink_rest
    end

    -- assign base32 skylink to be used in proxy_pass
    ngx.var.skylink_base32 = require("skynet.skylink").base32(ngx.var.skylink)
}

# host header has to be adjusted to properly match server name
proxy_set_header Host $skylink_base32.$skynet_portal_domain;

# pass the skylink request to subdomain skylink server
proxy_pass $scheme://$server_addr$path$is_args$args;

# in case siad returns location header, we need to replace the skylink with the domain name
header_filter_by_lua_block {
    ngx.header["Skynet-Portal-Api"] = ngx.var.scheme .. "://" .. ngx.var.skynet_portal_domain
    ngx.header["Skynet-Server-Api"] = ngx.var.scheme .. "://" .. ngx.var.skynet_server_domain

    if ngx.header.location then
        -- match location redirect part after the skylink
        local path = string.match(ngx.header.location, "[^/?]+(.*)");

        -- because siad will set the location header to ie. XABvi7JtJbQSMAcDwnUnmp2FKDPjg8_tTTFP4BwMSxVdEg/index.html
        -- we need to replace the skylink with the domain_name so we are not redirected to skylink
        ngx.header.location = ngx.var.hns_domain .. path
    end
}