package seo_test

import (
	"encoding/json"
	"errors"
	"net/http"
	"sort"
	"strings"
	"testing"

	"git.golem15.com/golem15/sm-seo-plugin/classes"
	"git.golem15.com/golem15/sm-seo-plugin/models"
	"gorm.io/gorm"
)

// redirectRow is a stored redirect as the tests read it.
type redirectRow struct {
	ID            uint
	Source        string
	Match         string
	Target        string
	Status        int
	Query         string
	IgnoreCase    bool
	TrailingSlash bool
	Origin        string
}

// redirects returns every stored redirect in id order.
func (e *testEnv) redirects(t *testing.T) []redirectRow {
	t.Helper()
	var rows []redirectRow
	if err := e.db.Raw(`SELECT id, source, match, target, status, query, ignore_case, trailing_slash, origin FROM golem15_seo_redirects ORDER BY id`).Scan(&rows).Error; err != nil {
		t.Fatal(err)
	}
	return rows
}

// redirectTo returns the target of the exact redirect of source, "" when
// there is none.
func redirectTo(rows []redirectRow, source string) string {
	for _, r := range rows {
		if r.Source == source && r.Match == "exact" {
			return r.Target
		}
	}
	return ""
}

// seedRedirect stores a redirect directly.
func (e *testEnv) seedRedirect(t *testing.T, source, match, target string, status int) {
	t.Helper()
	if err := e.db.Exec(`INSERT INTO golem15_seo_redirects (source, match, target, status, created_at, updated_at) VALUES (?, ?, ?, ?, NOW(), NOW())`,
		source, match, target, status).Error; err != nil {
		t.Fatal(err)
	}
}

// saveNotices returns the save notices of an admin save response.
func saveNotices(t *testing.T, body []byte) []struct{ Field, Message string } {
	t.Helper()
	var out struct {
		Meta struct {
			Notices []struct {
				Field   string `json:"field"`
				Message string `json:"message"`
			} `json:"notices"`
		} `json:"meta"`
	}
	if err := json.Unmarshal(body, &out); err != nil {
		t.Fatal(err)
	}
	var notices []struct{ Field, Message string }
	for _, n := range out.Meta.Notices {
		notices = append(notices, struct{ Field, Message string }{n.Field, n.Message})
	}
	return notices
}

// TestSlugChange301 is the plan's tracer (SC-3, D-18): an editor changes a
// published page's slug in the admin; inside the save a 301 from the old
// address to the new one is created, an earlier redirect to the old
// address is pointed straight at the new one, the editor gets the
// redirects.auto_created notice, and the resolve answer redirects the old
// address in one hop.
func TestSlugChange301(t *testing.T) {
	env := bootEnv(t)
	token := env.admin(t, true)
	id := env.createPage(t, token, map[string]any{"title": "Alpha", "slug": "a", "published": true})
	env.seedRedirect(t, "/pages/x", "exact", "/pages/a", 301)

	rec := env.expect(t, http.StatusOK, http.MethodPut, adminAPI("/acme/pages/pages/"+id), token, map[string]any{
		"title": "Alpha", "slug": "b", "published": true,
	})
	var found bool
	for _, n := range saveNotices(t, rec.Body.Bytes()) {
		if n.Field == "slug" && strings.Contains(n.Message, "“/pages/a”") && strings.Contains(n.Message, "“/pages/b”") && strings.Contains(n.Message, "1 earlier") {
			found = true
		}
	}
	if !found {
		t.Fatalf("update notices lack redirects.auto_created on slug: %s", rec.Body.String())
	}

	got := env.resolve(t, "/pages/a")
	if got["action"] != "redirect" || got["status"] != float64(301) || got["location"] != siteURL+"/pages/b" {
		t.Fatalf("resolve /pages/a = %v, want redirect 301 to %s/pages/b", got, siteURL)
	}
	if got := env.resolve(t, "/pages/b"); got["action"] != "ok" {
		t.Fatalf("resolve /pages/b = %v, want ok", got)
	}
	rows := env.redirects(t)
	if target := redirectTo(rows, "/pages/x"); target != "/pages/b" {
		t.Fatalf("earlier redirect /pages/x -> %q, want flattened to /pages/b (%+v)", target, rows)
	}
	if target := redirectTo(rows, "/pl/pages/a"); target != "/pl/pages/b" {
		t.Fatalf("pl redirect /pl/pages/a -> %q, want /pl/pages/b (%+v)", target, rows)
	}
	for _, r := range rows {
		if r.Source == "/pages/a" && r.Origin != "slug" {
			t.Fatalf("address-change redirect origin = %q, want slug", r.Origin)
		}
	}
	if got := env.resolve(t, "/pages/x"); got["location"] != siteURL+"/pages/b" {
		t.Fatalf("resolve /pages/x = %v, want one hop to /pages/b", got)
	}
}

// saveRedirect stores r through the service in its own transaction.
func (e *testEnv) saveRedirect(t *testing.T, r models.Redirect) (classes.RedirectCheck, error) {
	t.Helper()
	svc := e.seoPlugin(t).Service()
	var check classes.RedirectCheck
	err := e.db.Transaction(func(tx *gorm.DB) error {
		c, err := svc.SaveRedirect(t.Context(), tx, &r)
		check = c
		return err
	})
	return check, err
}

// mustRedirect stores r and fails on a refusal.
func (e *testEnv) mustRedirect(t *testing.T, source, match, target string, status int, opts ...func(*models.Redirect)) classes.RedirectCheck {
	t.Helper()
	r := models.NewRedirect()
	r.Source, r.Match, r.Target, r.Status = source, match, target, status
	for _, o := range opts {
		o(&r)
	}
	check, err := e.saveRedirect(t, r)
	if err != nil {
		t.Fatalf("save %s -> %s: %v", source, target, err)
	}
	return check
}

// refusedOn asserts that saving r is refused with key on field.
func (e *testEnv) refusedOn(t *testing.T, r models.Redirect, field, key string) {
	t.Helper()
	_, err := e.saveRedirect(t, r)
	var problems *classes.ProblemsError
	if !errors.As(err, &problems) {
		t.Fatalf("save %+v: err = %v, want a refusal on %s", r, err, field)
	}
	for _, p := range problems.Problems[field] {
		if p.Key == key {
			return
		}
	}
	t.Fatalf("save %+v: problems = %+v, want %s on %s", r, problems.Problems, key, field)
}

// expectRedirect asserts that target resolves to a redirect to location.
func (e *testEnv) expectRedirect(t *testing.T, target string, status int, location string) {
	t.Helper()
	got := e.resolve(t, target)
	if got["action"] != "redirect" || got["status"] != float64(status) || got["location"] != location {
		t.Fatalf("resolve %s = %v, want redirect %d to %s", target, got, status, location)
	}
}

// expectAction asserts the resolve action of target.
func (e *testEnv) expectAction(t *testing.T, target, action string) map[string]any {
	t.Helper()
	got := e.resolve(t, target)
	if got["action"] != action {
		t.Fatalf("resolve %s = %v, want %s", target, got, action)
	}
	return got
}

// TestRedirectEngine checks the redirect engine through the service and
// the resolve answer (D-16, D-17, D-19, T-32-16, T-32-17): matching
// options, order, statuses, refusals, loops, chains and the back-and-forth
// address change.
func TestRedirectEngine(t *testing.T) {
	env := bootEnv(t)
	svc := env.seoPlugin(t).Service()
	ignoreCase := func(r *models.Redirect) { r.IgnoreCase = true }
	noSlash := func(r *models.Redirect) { r.TrailingSlash = false }
	pass := func(r *models.Redirect) { r.Query = models.QueryPass }

	env.mustRedirect(t, "/old", "exact", "/new", 301)
	env.expectRedirect(t, "/old", 301, siteURL+"/new")
	env.expectRedirect(t, "/old/", 301, siteURL+"/new")
	env.expectRedirect(t, "/old?a=1", 301, siteURL+"/new")
	env.expectAction(t, "/OLD", "not_found")

	env.mustRedirect(t, "/Case", "exact", "/case-new", 302, ignoreCase)
	env.expectRedirect(t, "/CASE", 302, siteURL+"/case-new")
	env.mustRedirect(t, "/strict", "exact", "/strict-new", 301, noSlash)
	env.expectAction(t, "/strict/", "not_found")

	env.mustRedirect(t, "/p-old", "exact", "/p-new", 301, pass)
	env.expectRedirect(t, "/p-old?a=1&b=2", 301, siteURL+"/p-new?a=1&b=2")
	env.mustRedirect(t, "/q?id=5", "exact", "/q5", 301, pass)
	env.expectRedirect(t, "/q?id=5", 301, siteURL+"/q5")
	env.expectAction(t, "/q?id=6", "not_found")

	env.mustRedirect(t, "/w/*", "pattern", "/nw/*", 301)
	env.expectRedirect(t, "/w/x/y", 301, siteURL+"/nw/x/y")
	env.mustRedirect(t, `^/p/(\d+)$`, "regex", "/post/$1", 301)
	env.expectRedirect(t, "/p/12", 301, siteURL+"/post/12")
	env.expectAction(t, "/p/abc", "not_found")

	env.mustRedirect(t, "/w/exact", "exact", "/exact-wins", 301)
	env.mustRedirect(t, `^/w/.*$`, "regex", "/regex-loses", 301)
	env.expectRedirect(t, "/w/exact", 301, siteURL+"/exact-wins")
	env.expectRedirect(t, "/w/z", 301, siteURL+"/nw/z")

	env.mustRedirect(t, "/gone", "exact", "", 410)
	got := env.expectAction(t, "/gone", "gone")
	if got["status"] != float64(410) || got["location"] != nil {
		t.Fatalf("gone answer = %v, want 410 without a location", got)
	}

	newRule := func(source, match, target string, status int) models.Redirect {
		r := models.NewRedirect()
		r.Source, r.Match, r.Target, r.Status = source, match, target, status
		return r
	}
	env.refusedOn(t, newRule("/g2", "exact", "/x", 410), "target", "golem15.seo::lang.redirects.target_gone")
	env.refusedOn(t, newRule("/g3", "exact", "", 301), "target", "golem15.seo::lang.redirects.target_required")
	env.refusedOn(t, newRule("/g4", "exact", "elsewhere", 301), "target", "golem15.seo::lang.redirects.target_invalid")
	env.refusedOn(t, newRule(`^/(`, "regex", "/x", 301), "source", "golem15.seo::lang.redirects.regex_invalid")
	env.refusedOn(t, newRule("^/"+strings.Repeat("a", 520), "regex", "/x", 301), "source", "golem15.seo::lang.redirects.regex_invalid")
	env.refusedOn(t, newRule("/old", "exact", "/other", 301), "source", "golem15.seo::lang.redirects.source_taken")
	env.refusedOn(t, newRule("old", "exact", "/other", 301), "source", "golem15.seo::lang.redirects.source_invalid")
	env.refusedOn(t, newRule("/a*", "exact", "/other", 301), "source", "golem15.seo::lang.redirects.source_invalid")

	// Loops are refused; chains are saved with a notice (D-19).
	env.mustRedirect(t, "/la", "exact", "/lb", 301)
	_, err := env.saveRedirect(t, newRule("/lb", "exact", "/la", 301))
	var loop *classes.LoopError
	if !errors.As(err, &loop) || loop.Check.PathText() != "/lb → /la → /lb" {
		t.Fatalf("B -> A after A -> B: err = %v, want a loop /lb → /la → /lb", err)
	}
	if !strings.Contains(svc.LoopMessage(t.Context(), loop.Check), "/lb → /la → /lb") {
		t.Fatalf("loop message = %q", svc.LoopMessage(t.Context(), loop.Check))
	}
	_, err = env.saveRedirect(t, newRule("/grow/*", "pattern", "/grow/new/*", 301))
	if !errors.As(err, &loop) {
		t.Fatalf("/grow/* -> /grow/new/*: err = %v, want a loop (pattern probe)", err)
	}
	_, err = env.saveRedirect(t, newRule(`^/rx/(\d+)$`, "regex", "/rx/$1", 301))
	if !errors.As(err, &loop) {
		t.Fatalf("regex onto itself: err = %v, want a loop (regex probe)", err)
	}
	env.mustRedirect(t, "/cb", "exact", "/cc", 301)
	check := env.mustRedirect(t, "/ca", "exact", "/cb", 301)
	if !check.Chain || check.Final != "/cc" || check.Hops != 2 || check.PathText() != "/ca → /cb → /cc" {
		t.Fatalf("A -> B with B -> C: check = %+v, want a chain to /cc", check)
	}
	check = env.mustRedirect(t, "/cz", "exact", "/ca", 301)
	if !check.Chain || check.Final != "/cc" || check.Hops != 3 {
		t.Fatalf("Z -> A -> B -> C: check = %+v, want a 3-hop chain to /cc", check)
	}
	env.expectRedirect(t, "/cz", 301, siteURL+"/cc")
	check = env.mustRedirect(t, "/lone", "exact", "/somewhere", 301)
	if check.Chain || check.Loop {
		t.Fatalf("a single redirect: check = %+v, want neither chain nor loop", check)
	}

	// Slug back and forth (RESEARCH Pitfall 11): A→B, B→A, then A→C ends
	// with exactly A→C and B→C.
	for _, step := range [][2]string{{"/fa", "/fb"}, {"/fb", "/fa"}, {"/fa", "/fc"}} {
		if err := env.db.Transaction(func(tx *gorm.DB) error {
			_, err := svc.AddressChanged(t.Context(), tx, classes.AddressChange{Old: step[0], New: step[1]})
			return err
		}); err != nil {
			t.Fatal(err)
		}
	}
	var back []string
	for _, r := range env.redirects(t) {
		if strings.HasPrefix(r.Source, "/f") {
			back = append(back, r.Source+"->"+r.Target)
		}
	}
	sort.Strings(back)
	if strings.Join(back, ",") != "/fa->/fc,/fb->/fc" {
		t.Fatalf("back and forth = %v, want exactly /fa->/fc and /fb->/fc", back)
	}

	// A capture never turns an internal target into another host
	// (T-32-16); an absolute literal keeps its own host.
	env.mustRedirect(t, `^/r/(.*)$`, "regex", "/$1", 301)
	got = env.resolve(t, "/r//evil.example/x")
	if loc, _ := got["location"].(string); got["action"] != "redirect" || !strings.HasPrefix(loc, siteURL+"/") || strings.HasPrefix(loc, siteURL+"//") {
		t.Fatalf("protocol-relative capture = %v, want a path on the site", got)
	}
	env.mustRedirect(t, `^/ext/(.*)$`, "regex", "https://partner.example/$1", 301)
	env.expectRedirect(t, "/ext/x", 301, "https://partner.example/x")
	env.seedRedirect(t, `^/ext2(.*)$`, "regex", "https://partner.example$1", 301)
	if got := env.resolve(t, "/ext2@evil.example"); got["action"] == "redirect" {
		t.Fatalf("capture into the host = %v, want no redirect", got)
	}
	env.mustRedirect(t, "/qp/*", "pattern", "/nq/*", 301, pass)
	got = env.resolve(t, "/qp/a?next=//evil.example")
	if loc, _ := got["location"].(string); !strings.HasPrefix(loc, siteURL+"/nq/a?") {
		t.Fatalf("passed query = %v, want it appended to the query only", got)
	}
}