package main

import (
	"bytes"
	"io"
	"net/http"
	"net/http/httptest"
	"net/url"
	"os"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
	"testing"
)

// The environment mailu gives automx on novox when the fixtures were captured (files/mailu.env): the mail domain,
// the route name for both servers, the ports.
var capturedEnvironment = map[string]string{
	"AMX_MAIL_DOMAINS": "novox.be",
	"AMX_IMAP_ADDRESS": "mail.novox.be",
	"AMX_IMAP_PORT":    "143",
	"AMX_SMTP_ADDRESS": "mail.novox.be",
	"AMX_SMTP_PORT":    "587",
	"AUTOMX_PORT":      "4243",
}

func getenvOf(m map[string]string) func(string) string {
	return func(k string) string { return m[k] }
}

func testServer(t *testing.T) *httptest.Server {
	t.Helper()
	cfg, err := configFrom(getenvOf(capturedEnvironment))
	if err != nil {
		t.Fatal(err)
	}
	s := httptest.NewServer(newHandler(cfg))
	t.Cleanup(s.Close)
	return s
}

const captured = "testdata/captured"

// A captured request: its first line is the method and the URL the client used, then the headers sent, then after
// a blank line the body sent (CAPTURED, how the files were written).
type request struct {
	method, url string
	header      [][2]string
	body        string
}

func readRequest(t *testing.T, stem string) request {
	t.Helper()
	raw, err := os.ReadFile(stem + ".request")
	if err != nil {
		t.Fatal(err)
	}
	head, body, hasBody := strings.Cut(string(raw), "\n\n")
	if !hasBody {
		head = strings.TrimSuffix(head, "\n")
	}
	lines := strings.Split(head, "\n")
	method, target, ok := strings.Cut(lines[0], " ")
	if !ok {
		t.Fatalf("%s: first line %q is not METHOD URL", stem, lines[0])
	}
	r := request{method: method, url: target, body: body}
	for _, l := range lines[1:] {
		k, v, ok := strings.Cut(l, ": ")
		if !ok {
			t.Fatalf("%s: header line %q", stem, l)
		}
		r.header = append(r.header, [2]string{k, v})
	}
	return r
}

func readFile(t *testing.T, name string) string {
	t.Helper()
	b, err := os.ReadFile(name)
	if err != nil {
		t.Fatal(err)
	}
	return string(b)
}

// A fixture asks for its body to differ only where DIFFERENCES says so: a stem with a .corrected.body is answered
// with that, and its Content-Length is the corrected body's.
func expectedBody(t *testing.T, stem string) (body string, corrected bool) {
	if _, err := os.Stat(stem + ".corrected.body"); err == nil {
		return readFile(t, stem+".corrected.body"), true
	}
	return readFile(t, stem+".body"), false
}

func TestEveryCapturedRequestIsAnsweredAsAutomxAnswered(t *testing.T) {
	stems, _ := filepath.Glob(filepath.Join(captured, "*.request"))
	if len(stems) < 17 {
		t.Fatalf("%d captured requests found, want the 17 of issue 1630", len(stems))
	}
	srv := testServer(t)
	client := &http.Client{CheckRedirect: func(*http.Request, []*http.Request) error { return http.ErrUseLastResponse }}
	for _, f := range stems {
		stem := strings.TrimSuffix(f, ".request")
		t.Run(filepath.Base(stem), func(t *testing.T) {
			rq := readRequest(t, stem)
			u, err := url.Parse(rq.url)
			if err != nil {
				t.Fatal(err)
			}
			// The mesh's route reaches the program with the client's name and scheme; the program is told them in
			// the forwarding headers (the Location of fixture 14 holds them).
			req, err := http.NewRequest(rq.method, srv.URL+u.RequestURI(), strings.NewReader(rq.body))
			if err != nil {
				t.Fatal(err)
			}
			for _, h := range rq.header {
				req.Header.Set(h[0], h[1])
			}
			req.Host = u.Host
			req.Header.Set("X-Forwarded-Proto", u.Scheme)
			resp, err := client.Do(req)
			if err != nil {
				t.Fatal(err)
			}
			defer resp.Body.Close()
			got, _ := io.ReadAll(resp.Body)

			if want := strings.TrimRight(readFile(t, stem+".status"), "\n"); resp.Status != want {
				t.Errorf("status %q, captured %q", resp.Status, want)
			}
			wantBody, corrected := expectedBody(t, stem)
			if !bytes.Equal(got, []byte(wantBody)) {
				t.Errorf("body\n%q\nwant\n%q", got, wantBody)
			}
			want := map[string]string{}
			for _, l := range strings.Split(strings.TrimRight(readFile(t, stem+".headers"), "\n"), "\n") {
				if k, v, ok := strings.Cut(l, ": "); ok {
					want[k] = v
				}
			}
			if corrected {
				want["Content-Length"] = strconv.Itoa(len(wantBody))
			}
			// Server names the Python program that answered (DIFFERENCES); Date changes on every request.
			delete(want, "Server")
			var extra []string
			for k := range resp.Header {
				if k == "Date" || k == "Server" {
					continue
				}
				if _, ok := want[k]; !ok {
					extra = append(extra, k)
				}
			}
			sort.Strings(extra)
			if len(extra) > 0 {
				t.Errorf("headers the capture does not have: %v", extra)
			}
			for k, v := range want {
				if g := resp.Header.Get(k); g != v {
					t.Errorf("header %s: %q, captured %q", k, g, v)
				}
			}
		})
	}
}

// DIFFERENCES: the one change clause 9 of ADR 0480 allows to an answer is the IMAP server's name, written from
// AMX_IMAP_ADDRESS where automx wrote an empty one.
func TestTheOnlyCorrectedAnswerIsTheImapServersName(t *testing.T) {
	corrected, _ := filepath.Glob(filepath.Join(captured, "*.corrected.body"))
	if len(corrected) != 3 {
		t.Fatalf("%d corrected answers, want the three Thunderbird answers (01, 02, 03): %v", len(corrected), corrected)
	}
	for _, c := range corrected {
		orig := readFile(t, strings.TrimSuffix(c, ".corrected.body")+".body")
		want := strings.Replace(orig, "<hostname />", "<hostname>mail.novox.be</hostname>", 1)
		if strings.Contains(want, "<hostname />") || want == orig {
			t.Fatalf("%s: the capture has no single empty hostname to correct", c)
		}
		if got := readFile(t, c); got != want {
			t.Errorf("%s differs from the capture by more than the IMAP server's name", c)
		}
	}
}

func TestTheImapServerIsNamedFromTheImapAddress(t *testing.T) {
	env := map[string]string{}
	for k, v := range capturedEnvironment {
		env[k] = v
	}
	env["AMX_IMAP_ADDRESS"] = "imap.example.test"
	env["AMX_IMAP_PORT"] = "993"
	cfg, err := configFrom(getenvOf(env))
	if err != nil {
		t.Fatal(err)
	}
	rec := httptest.NewRecorder()
	newHandler(cfg).ServeHTTP(rec, httptest.NewRequest("GET", "/mail/config-v1.1.xml?emailaddress=a@novox.be", nil))
	body := rec.Body.String()
	if !strings.Contains(body, `<incomingServer type="imap"><hostname>imap.example.test</hostname><port>993</port>`) {
		t.Errorf("incoming server not named from AMX_IMAP_ADDRESS and AMX_IMAP_PORT: %s", body)
	}
	if !strings.Contains(body, `<outgoingServer type="smtp"><hostname>mail.novox.be</hostname><port>587</port>`) {
		t.Errorf("outgoing server changed: %s", body)
	}
}

func TestEveryDomainOfTheEnvironmentIsServed(t *testing.T) {
	env := map[string]string{}
	for k, v := range capturedEnvironment {
		env[k] = v
	}
	env["AMX_MAIL_DOMAINS"] = "novox.be, example.test"
	cfg, err := configFrom(getenvOf(env))
	if err != nil {
		t.Fatal(err)
	}
	h := newHandler(cfg)
	for _, d := range []string{"novox.be", "example.test"} {
		rec := httptest.NewRecorder()
		h.ServeHTTP(rec, httptest.NewRequest("GET", "/mail/config-v1.1.xml?emailaddress=a@"+d, nil))
		if rec.Code != 200 || !strings.Contains(rec.Body.String(), "<domain>"+d+"</domain>") {
			t.Errorf("%s: %d %s", d, rec.Code, rec.Body.String())
		}
	}
}

// Failure is loud (issue 1631 AC2): a missing variable stops the program and its name is in the message.
func TestAMissingVariableStopsTheProgramNamingIt(t *testing.T) {
	for name := range capturedEnvironment {
		t.Run(name, func(t *testing.T) {
			env := map[string]string{}
			for k, v := range capturedEnvironment {
				env[k] = v
			}
			delete(env, name)
			if _, err := configFrom(getenvOf(env)); err == nil || !strings.Contains(err.Error(), name) {
				t.Fatalf("configFrom without %s: %v", name, err)
			}
			var out bytes.Buffer
			if code := run(getenvOf(env), &out, func(*http.Server) error { t.Fatal("served without its configuration"); return nil }); code == 0 || !strings.Contains(out.String(), name) {
				t.Errorf("run without %s: exit %d, said %q", name, code, out.String())
			}
		})
	}
}

func TestAPortThatIsNotANumberIsRefusedNamingIt(t *testing.T) {
	env := map[string]string{}
	for k, v := range capturedEnvironment {
		env[k] = v
	}
	env["AMX_SMTP_PORT"] = "submission"
	if _, err := configFrom(getenvOf(env)); err == nil || !strings.Contains(err.Error(), "AMX_SMTP_PORT") {
		t.Fatalf("got %v", err)
	}
}