refactor: move TH structs and definitions to model (#894)

This commit moves the TH structs and definitions to model. We don't want
oohelperd to depend on web_connectivity@v0.4.

Part of https://github.com/ooni/probe/issues/2240

internal/model/th.go

@@ -0,0 +1,85 @@
+package model
+
+// THDNSNameError is the error returned by the control on NXDOMAIN
+const THDNSNameError = "dns_name_error"
+
+// THRequest is the request that we send to the control
+type THRequest struct {
+	HTTPRequest        string              `json:"http_request"`
+	HTTPRequestHeaders map[string][]string `json:"http_request_headers"`
+	TCPConnect         []string            `json:"tcp_connect"`
+}
+
+// THTCPConnectResult is the result of the TCP connect
+// attempt performed by the control vantage point.
+type THTCPConnectResult struct {
+	Status  bool    `json:"status"`
+	Failure *string `json:"failure"`
+}
+
+// THTLSHandshakeResult is the result of the TLS handshake
+// attempt performed by the control vantage point.
+type THTLSHandshakeResult struct {
+	ServerName string  `json:"server_name"`
+	Status     bool    `json:"status"`
+	Failure    *string `json:"failure"`
+}
+
+// THHTTPRequestResult is the result of the HTTP request
+// performed by the control vantage point.
+type THHTTPRequestResult struct {
+	BodyLength int64             `json:"body_length"`
+	Failure    *string           `json:"failure"`
+	Title      string            `json:"title"`
+	Headers    map[string]string `json:"headers"`
+	StatusCode int64             `json:"status_code"`
+}
+
+// TODO(bassosimone): ASNs is a private implementation detail of v0.4
+// that is actually ~annoying because we are mixing the data model with fields used
+// by just the v0.4 client implementation. We should avoid repeating this mistake
+// when implementing v0.5 of the client and eventually remove ASNs.
+
+// THDNSResult is the result of the DNS lookup
+// performed by the control vantage point.
+type THDNSResult struct {
+	Failure *string  `json:"failure"`
+	Addrs   []string `json:"addrs"`
+	ASNs    []int64  `json:"-"` // not visible from the JSON
+}
+
+// THIPInfo contains information about IP addresses resolved either
+// by the probe or by the TH and processed by the TH.
+type THIPInfo struct {
+	// ASN contains the address' AS number.
+	ASN int64 `json:"asn"`
+
+	// Flags contains flags describing this address.
+	Flags int64 `json:"flags"`
+}
+
+const (
+	// THIPInfoFlagResolvedByProbe indicates that the probe has
+	// resolved this IP address.
+	THIPInfoFlagResolvedByProbe = 1 << iota
+
+	// THIPInfoFlagResolvedByTH indicates that the test helper
+	// has resolved this IP address.
+	THIPInfoFlagResolvedByTH
+
+	// THIPInfoFlagIsBogon indicates that the address is a bogon
+	THIPInfoFlagIsBogon
+
+	// THIPInfoFlagValidForDomain indicates that an IP address
+	// is valid for the domain because it works with TLS
+	THIPInfoFlagValidForDomain
+)
+
+// THResponse is the response from the control service.
+type THResponse struct {
+	TCPConnect   map[string]THTCPConnectResult   `json:"tcp_connect"`
+	TLSHandshake map[string]THTLSHandshakeResult `json:"tls_handshake"`
+	HTTPRequest  THHTTPRequestResult             `json:"http_request"`
+	DNS          THDNSResult                     `json:"dns"`
+	IPInfo       map[string]*THIPInfo            `json:"ip_info"`
+}