package cabana

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"reflect"
	"strconv"
	"strings"
	"time"

	"git.golem15.com/golem15/summercms/backpack"
	"git.golem15.com/golem15/summercms/bouncer"
	"git.golem15.com/golem15/summercms/pact"
	"git.golem15.com/golem15/summercms/party"
	"git.golem15.com/golem15/summercms/phrasebook"
	"gorm.io/gorm"
)

// Routes is the raw admin API mounted by surf.BuildRouter.
type Routes struct {
	Middleware pact.Middleware
	Mount      func(r pact.Router)
}

type service struct {
	app        *backpack.App
	reg        *Registry
	secret     string
	ttl        time.Duration
	refreshTTL time.Duration
	grace      time.Duration
	bcryptCost int
	loginMax   int
	loginDecay int
	issuer     string
	bl         bouncer.BlacklistStore
}

// Activate compiles admin controllers and, when any exist, requires
// admin.jwt.secret. No controllers means no admin routes and no secret check.
func Activate(app *backpack.App, plugins []party.Plugin) (*Routes, error) {
	items, err := collectControllers(plugins)
	if err != nil {
		return nil, err
	}
	if len(items) == 0 {
		return nil, nil
	}
	secret, err := adminSecret(app)
	if err != nil {
		return nil, err
	}
	reg, err := compileRegistry(items)
	if err != nil {
		return nil, err
	}
	if err := compileContributions(reg, plugins); err != nil {
		return nil, err
	}
	if app == nil {
		return nil, errors.New("cabana: app is nil")
	}
	guards, ok := app.Lookup[*bouncer.Registry]()
	if !ok || guards == nil {
		guards = bouncer.NewRegistry()
		if err := app.Publish(guards); err != nil {
			return nil, err
		}
	}
	bl := adminBlacklist(app)
	guard := bouncer.NewBackendJWTGuard(secret, lazyBackendUsers{app: app, reg: reg}, bl, writeUnauthenticated)
	if _, err := guards.Middleware("backend"); err != nil {
		if err := guards.Register("summercms.cabana", "backend", guard); err != nil {
			return nil, err
		}
	}
	mw, err := guards.Middleware("backend")
	if err != nil {
		return nil, err
	}
	loginMax, loginDecay := adminLoginWindow(app)
	svc := &service{
		app:        app,
		reg:        reg,
		secret:     secret,
		ttl:        adminTTL(app),
		refreshTTL: adminRefreshTTL(app),
		grace:      adminGrace(app),
		bcryptCost: adminBcryptCost(app),
		loginMax:   loginMax,
		loginDecay: loginDecay,
		issuer:     adminIssuer(app),
		bl:         bl,
	}
	return &Routes{Middleware: mw, Mount: svc.mount}, nil
}

func writeUnauthenticated(w http.ResponseWriter, _ error) {
	WriteError(w, http.StatusUnauthorized, "unauthenticated", msgUnauthenticated)
}

type lazyBackendUsers struct {
	app *backpack.App
	reg *Registry
}

func (p lazyBackendUsers) FindByID(ctx context.Context, id uint) (*bouncer.Principal, error) {
	if p.app == nil {
		return nil, errors.New("cabana: database is not configured")
	}
	db, ok := p.app.Lookup[*gorm.DB]()
	if !ok || db == nil {
		return nil, errors.New("cabana: database is not configured")
	}
	return (BackendUsers{DB: db, Registry: p.reg}).FindByID(ctx, id)
}

func (s *service) mount(r pact.Router) {
	throttle := fmt.Sprintf("throttle:%d,%d", s.loginMax, s.loginDecay)
	r.GroupRaw("/_admin/api/v1/auth", nil, func(g pact.Router) {
		g.Post("/login", s.login, throttle)
		g.Post("/refresh", s.refresh)
	})
	r.GroupRaw("/_admin/api/v1", []string{"backend"}, func(g pact.Router) {
		g.Post("/auth/logout", s.logout)
		g.Get("/auth/me", s.me)
		g.Get("/navigation", s.navigation)
		g.Get("/settings", s.settingsList)
		g.Get("/settings/{code}/schema", s.settingsSchema)
		constrainSetting(g)
		g.Get("/settings/{code}", s.settingsGet)
		constrainSetting(g)
		g.Put("/settings/{code}", s.settingsPut)
		constrainSetting(g)
		g.Get("/{vendor}/{plugin}/{controller}/schema/list", s.listSchema)
		constrainController(g)
		g.Get("/{vendor}/{plugin}/{controller}/schema/form", s.formSchema)
		constrainController(g)
		g.Get("/{vendor}/{plugin}/{controller}/schema/relation/{name}", s.relationSchema)
		constrainRelation(g)
		g.Get("/{vendor}/{plugin}/{controller}", s.list)
		constrainController(g)
		g.Post("/{vendor}/{plugin}/{controller}", s.create)
		constrainController(g)
		g.Post("/{vendor}/{plugin}/{controller}/bulk-delete", s.bulkDelete)
		constrainController(g)
		g.Get("/{vendor}/{plugin}/{controller}/{id}", s.show)
		constrainController(g)
		g.Put("/{vendor}/{plugin}/{controller}/{id}", s.update)
		constrainController(g)
		g.Delete("/{vendor}/{plugin}/{controller}/{id}", s.deleteRecord)
		constrainController(g)
		g.Get("/{vendor}/{plugin}/{controller}/{id}/relations/{name}", s.relationLinked)
		constrainRelation(g)
		g.Get("/{vendor}/{plugin}/{controller}/{id}/relations/{name}/candidates", s.relationCandidates)
		constrainRelation(g)
		g.Post("/{vendor}/{plugin}/{controller}/{id}/relations/{name}/link", s.relationLink)
		constrainRelation(g)
		g.Post("/{vendor}/{plugin}/{controller}/{id}/relations/{name}/unlink", s.relationUnlink)
		constrainRelation(g)
	})
}

func constrainController(g pact.Router) {
	g.Where("vendor", "[A-Za-z0-9_-]+")
	g.Where("plugin", "[A-Za-z0-9_-]+")
	g.Where("controller", "[A-Za-z0-9_-]+")
}

func constrainRelation(g pact.Router) {
	constrainController(g)
	g.Where("name", "[A-Za-z_][A-Za-z0-9_]*")
}

func constrainSetting(g pact.Router) {
	g.Where("code", "[A-Za-z_][A-Za-z0-9_-]*")
}

func (s *service) navigation(w http.ResponseWriter, r *http.Request) {
	principal, ok := bouncer.User(r.Context())
	if !ok || principal == nil || !principal.Backend {
		WriteError(w, http.StatusUnauthorized, "unauthenticated", msgUnauthenticated)
		return
	}
	navigation, _ := s.reg.Metadata(r.Context(), principal, s.translator())
	WriteData(w, http.StatusOK, navigation, map[string]any{"locale": schemaLocale(r.Context(), s.translator())})
}

func (s *service) settingsList(w http.ResponseWriter, r *http.Request) {
	principal, ok := bouncer.User(r.Context())
	if !ok || principal == nil || !principal.Backend {
		WriteError(w, http.StatusUnauthorized, "unauthenticated", msgUnauthenticated)
		return
	}
	_, settings := s.reg.Metadata(r.Context(), principal, s.translator())
	WriteData(w, http.StatusOK, settings, map[string]any{"locale": schemaLocale(r.Context(), s.translator())})
}

func (s *service) settingsSchema(w http.ResponseWriter, r *http.Request) {
	s.protectSetting(w, r, func(setting *CompiledSetting) {
		view, err := setting.Form.Localize(r.Context(), s.translator(), nil)
		if err != nil {
			WriteError(w, http.StatusInternalServerError, "error", msgServerError)
			return
		}
		WriteData(w, http.StatusOK, view, map[string]any{"locale": view.Meta.Locale})
	})
}

func (s *service) settingsGet(w http.ResponseWriter, r *http.Request) {
	s.protectSetting(w, r, func(setting *CompiledSetting) {
		db, err := s.db()
		if err != nil {
			WriteError(w, http.StatusInternalServerError, "error", msgServerError)
			return
		}
		result, err := (SettingsService{DB: db}).Get(r.Context(), setting)
		if err != nil {
			writeCRUDError(w, err)
			return
		}
		WriteData(w, http.StatusOK, result, nil)
	})
}

func (s *service) settingsPut(w http.ResponseWriter, r *http.Request) {
	s.protectSetting(w, r, func(setting *CompiledSetting) {
		body, err := decodeObject(r)
		if err != nil {
			writeCRUDError(w, err)
			return
		}
		db, err := s.db()
		if err != nil {
			WriteError(w, http.StatusInternalServerError, "error", msgServerError)
			return
		}
		result, err := (SettingsService{DB: db}).Put(r.Context(), setting, body)
		if err != nil {
			writeCRUDError(w, err)
			return
		}
		WriteData(w, http.StatusOK, result, nil)
	})
}

func (s *service) protectSetting(w http.ResponseWriter, r *http.Request, fn func(*CompiledSetting)) {
	principal, ok := bouncer.User(r.Context())
	if !ok || principal == nil || !principal.Backend {
		WriteError(w, http.StatusUnauthorized, "unauthenticated", msgUnauthenticated)
		return
	}
	setting, exists := s.reg.Setting(r.PathValue("code"))
	if !exists {
		WriteError(w, http.StatusNotFound, "not_found", msgNotFound)
		return
	}
	if !Allows(principal, setting.Item.Permissions) {
		WriteError(w, http.StatusForbidden, "forbidden", msgForbidden)
		return
	}
	fn(setting)
}

func (s *service) relationSchema(w http.ResponseWriter, r *http.Request) {
	s.protect(w, r, func(cc *CompiledController) {
		cr, err := relationOf(cc, r.PathValue("name"))
		if err != nil {
			writeCRUDError(w, err)
			return
		}
		tr := s.translator()
		view := cr.Schema.Localize(r.Context(), tr)
		meta := map[string]any{}
		if locale := schemaLocale(r.Context(), tr); locale != "" {
			meta["locale"] = locale
		}
		WriteData(w, http.StatusOK, view, meta)
	})
}

func relationQueryFromRequest(r *http.Request) RelationQuery {
	q := r.URL.Query()
	return RelationQuery{Search: q.Get("search"), Sort: q.Get("sort"), Dir: q.Get("dir"), Page: q.Get("page"), PerPage: q.Get("per_page")}
}

func (s *service) relationLinked(w http.ResponseWriter, r *http.Request) {
	s.relationList(w, r, false)
}

func (s *service) relationCandidates(w http.ResponseWriter, r *http.Request) {
	s.relationList(w, r, true)
}

func (s *service) relationList(w http.ResponseWriter, r *http.Request, candidates bool) {
	s.protect(w, r, func(cc *CompiledController) {
		id, err := pathID(r)
		if err != nil {
			writeCRUDError(w, err)
			return
		}
		svc, err := s.relations()
		if err != nil {
			WriteError(w, http.StatusInternalServerError, "error", msgServerError)
			return
		}
		var result *RelationResult
		if candidates {
			result, err = svc.Candidates(r.Context(), cc, r.PathValue("name"), id, relationQueryFromRequest(r))
		} else {
			result, err = svc.Linked(r.Context(), cc, r.PathValue("name"), id, relationQueryFromRequest(r))
		}
		if err != nil {
			writeCRUDError(w, err)
			return
		}
		WriteData(w, http.StatusOK, result.Data, map[string]any{"page": result.Meta.Page, "per_page": result.Meta.PerPage, "total": result.Meta.Total, "last_page": result.Meta.LastPage})
	})
}

func (s *service) relationLink(w http.ResponseWriter, r *http.Request) {
	s.relationMutation(w, r, true)
}

func (s *service) relationUnlink(w http.ResponseWriter, r *http.Request) {
	s.relationMutation(w, r, false)
}

func (s *service) relationMutation(w http.ResponseWriter, r *http.Request, link bool) {
	s.protect(w, r, func(cc *CompiledController) {
		id, err := pathID(r)
		if err != nil {
			writeCRUDError(w, err)
			return
		}
		in, err := decodeRelationMutation(r)
		if err != nil {
			writeCRUDError(w, err)
			return
		}
		svc, err := s.relations()
		if err != nil {
			WriteError(w, http.StatusInternalServerError, "error", msgServerError)
			return
		}
		var result RelationMutationResult
		if link {
			result, err = svc.Link(r.Context(), cc, r.PathValue("name"), id, in)
		} else {
			result, err = svc.Unlink(r.Context(), cc, r.PathValue("name"), id, in)
		}
		if err != nil {
			writeCRUDError(w, err)
			return
		}
		WriteData(w, http.StatusOK, result, nil)
	})
}

func decodeRelationMutation(r *http.Request) (RelationMutationInput, error) {
	dec := json.NewDecoder(r.Body)
	dec.UseNumber()
	dec.DisallowUnknownFields()
	var in RelationMutationInput
	if err := dec.Decode(&in); err != nil {
		return RelationMutationInput{}, relationInvalid("body", "The request body is invalid.")
	}
	var trailing any
	if err := dec.Decode(&trailing); err != io.EOF {
		return RelationMutationInput{}, relationInvalid("body", "The request body is invalid.")
	}
	return in, nil
}

func (s *service) relations() (RelationService, error) {
	db, err := s.db()
	if err != nil {
		return RelationService{}, err
	}
	return RelationService{DB: db}, nil
}

func (s *service) formSchema(w http.ResponseWriter, r *http.Request) {
	s.protect(w, r, func(cc *CompiledController) {
		if cc.Form == nil {
			WriteError(w, http.StatusNotFound, "not_found", msgNotFound)
			return
		}
		view, err := cc.Form.Localize(r.Context(), s.translator(), dropdownProvider(cc.Controller))
		if err != nil {
			WriteError(w, http.StatusInternalServerError, "error", msgServerError)
			return
		}
		meta := map[string]any{}
		if view.Meta.Locale != "" {
			meta["locale"] = view.Meta.Locale
		}
		WriteData(w, http.StatusOK, view, meta)
	})
}

func (s *service) listSchema(w http.ResponseWriter, r *http.Request) {
	s.protect(w, r, func(cc *CompiledController) {
		schema := cc.List
		if schema == nil {
			schema = &ListSchema{}
		}
		view, err := schema.Localize(r.Context(), s.translator())
		if err != nil {
			WriteError(w, http.StatusInternalServerError, "error", msgServerError)
			return
		}
		meta := map[string]any{}
		if view.Meta != nil {
			meta["locale"] = view.Meta.Locale
		}
		WriteData(w, http.StatusOK, view, meta)
	})
}

func (s *service) translator() *phrasebook.Translator {
	if s == nil || s.app == nil {
		return nil
	}
	tr, ok := s.app.Lookup[*phrasebook.Translator]()
	if !ok {
		return nil
	}
	return tr
}

func (s *service) show(w http.ResponseWriter, r *http.Request) {
	s.protect(w, r, func(cc *CompiledController) {
		id, err := pathID(r)
		if err != nil {
			writeCRUDError(w, err)
			return
		}
		svc, err := s.crud()
		if err != nil {
			WriteError(w, http.StatusInternalServerError, "error", msgServerError)
			return
		}
		rec, err := svc.Show(r.Context(), cc, id)
		if err != nil {
			writeCRUDError(w, err)
			return
		}
		WriteData(w, http.StatusOK, rec, nil)
	})
}

func (s *service) create(w http.ResponseWriter, r *http.Request) {
	s.protect(w, r, func(cc *CompiledController) {
		body, err := decodeObject(r)
		if err != nil {
			writeCRUDError(w, err)
			return
		}
		svc, err := s.crud()
		if err != nil {
			WriteError(w, http.StatusInternalServerError, "error", msgServerError)
			return
		}
		rec, err := svc.Create(r.Context(), cc, RecordInput{Body: body})
		if err != nil {
			writeCRUDError(w, err)
			return
		}
		WriteData(w, http.StatusCreated, rec, nil)
	})
}

func (s *service) update(w http.ResponseWriter, r *http.Request) {
	s.protect(w, r, func(cc *CompiledController) {
		id, err := pathID(r)
		if err != nil {
			writeCRUDError(w, err)
			return
		}
		body, err := decodeObject(r)
		if err != nil {
			writeCRUDError(w, err)
			return
		}
		svc, err := s.crud()
		if err != nil {
			WriteError(w, http.StatusInternalServerError, "error", msgServerError)
			return
		}
		rec, err := svc.Update(r.Context(), cc, id, RecordInput{Body: body})
		if err != nil {
			writeCRUDError(w, err)
			return
		}
		WriteData(w, http.StatusOK, rec, nil)
	})
}

func (s *service) bulkDelete(w http.ResponseWriter, r *http.Request) {
	s.protect(w, r, func(cc *CompiledController) {
		in, err := decodeBulk(r)
		if err != nil {
			writeCRUDError(w, err)
			return
		}
		svc, err := s.crud()
		if err != nil {
			WriteError(w, http.StatusInternalServerError, "error", msgServerError)
			return
		}
		result, err := svc.BulkDelete(r.Context(), cc, in)
		if err != nil {
			writeCRUDError(w, err)
			return
		}
		WriteData(w, http.StatusOK, result, nil)
	})
}

func decodeBulk(r *http.Request) (BulkDeleteInput, error) {
	dec := json.NewDecoder(r.Body)
	dec.UseNumber()
	var in BulkDeleteInput
	if err := dec.Decode(&in); err != nil {
		return BulkDeleteInput{}, &ValidationError{Details: map[string]any{"body": []string{"The request body is invalid."}}}
	}
	return in, nil
}

func (s *service) deleteRecord(w http.ResponseWriter, r *http.Request) {
	s.protect(w, r, func(cc *CompiledController) {
		id, err := pathID(r)
		if err != nil {
			writeCRUDError(w, err)
			return
		}
		svc, err := s.crud()
		if err != nil {
			WriteError(w, http.StatusInternalServerError, "error", msgServerError)
			return
		}
		result, err := svc.Delete(r.Context(), cc, id)
		if err != nil {
			writeCRUDError(w, err)
			return
		}
		WriteData(w, http.StatusOK, result, nil)
	})
}

func (s *service) crud() (CRUDService, error) {
	db, err := s.db()
	if err != nil {
		return CRUDService{}, err
	}
	return CRUDService{DB: db}, nil
}

func (s *service) list(w http.ResponseWriter, r *http.Request) {
	s.protect(w, r, func(cc *CompiledController) {
		db, err := s.db()
		if err != nil {
			WriteError(w, http.StatusInternalServerError, "error", msgServerError)
			return
		}
		result, err := ExecuteList(r.Context(), db, cc, listQueryFromRequest(r))
		var invalid *ListValidationError
		if errors.As(err, &invalid) {
			WriteErrorDetails(w, http.StatusUnprocessableEntity, "validation_failed", "Validation failed", invalid.Details)
			return
		}
		if err != nil {
			WriteError(w, http.StatusInternalServerError, "error", msgServerError)
			return
		}
		WriteData(w, http.StatusOK, result.Data, map[string]any{
			"page":      result.Meta.Page,
			"per_page":  result.Meta.PerPage,
			"total":     result.Meta.Total,
			"last_page": result.Meta.LastPage,
		})
	})
}

// protect runs after the backend guard. Controller lookup precedes permission
// evaluation, and schema/SQL run only inside fn.
func (s *service) protect(w http.ResponseWriter, r *http.Request, fn func(*CompiledController)) {
	id := r.PathValue("vendor") + "." + r.PathValue("plugin") + "." + r.PathValue("controller")
	cc, ok := s.reg.Get(id)
	if !ok {
		WriteError(w, http.StatusNotFound, "not_found", msgNotFound)
		return
	}
	principal, _ := bouncer.User(r.Context())
	if principal == nil || !principal.Backend {
		WriteError(w, http.StatusUnauthorized, "unauthenticated", msgUnauthenticated)
		return
	}
	if !Allows(principal, requiredOf(cc.Controller)) {
		s.logAuth(r, "denied", principal.ID)
		WriteError(w, http.StatusForbidden, "forbidden", msgForbidden)
		return
	}
	fn(cc)
}

func projectRow(row any, controller pact.AdminController, cols []ListColumn) map[string]any {
	v := reflect.ValueOf(row)
	for v.Kind() == reflect.Pointer {
		if v.IsNil() {
			return map[string]any{}
		}
		v = v.Elem()
	}
	out := make(map[string]any, len(cols)+1)
	if id := fieldByColumn(v, "id"); id.IsValid() && id.CanInterface() {
		out["id"] = id.Interface()
	}
	for _, col := range cols {
		if col.Relation != "" {
			if value, ok := relatedSelect(v, controller, col); ok {
				out[col.Key] = value
			}
			continue
		}
		field := fieldByColumn(v, col.Key)
		if !field.IsValid() || !field.CanInterface() {
			continue
		}
		out[col.Key] = field.Interface()
	}
	return out
}

func fieldByColumn(v reflect.Value, column string) reflect.Value {
	if v.Kind() != reflect.Struct {
		return reflect.Value{}
	}
	t := v.Type()
	for i := 0; i < t.NumField(); i++ {
		field := t.Field(i)
		if field.PkgPath != "" {
			continue
		}
		if gormColumn(field) == column || strings.EqualFold(field.Name, column) {
			return v.Field(i)
		}
	}
	return reflect.Value{}
}

func gormColumn(field reflect.StructField) string {
	for _, part := range strings.Split(field.Tag.Get("gorm"), ";") {
		part = strings.TrimSpace(part)
		if name, ok := strings.CutPrefix(part, "column:"); ok {
			return name
		}
	}
	return ""
}

func uitoa(id uint) string {
	return strconv.FormatUint(uint64(id), 10)
}