package server

import (
	"context"
	"net/http"
	"slices"
	"strconv"
	"strings"
	"time"

	"jarl/internal/api"
	"jarl/internal/auth"
	"jarl/internal/blocking"
	"jarl/internal/engine"
	"jarl/internal/model"
)

// ---- blocking (docs/blocking.md)

// bytesPerRecord is what named 9.20 needs per policy zone record and view,
// measured with lists of a few hundred thousand entries.
const bytesPerRecord = 630

func viewNames(st *model.State, ids []int64) []string {
	out := []string{}
	for _, id := range ids {
		if v := st.Views[id]; v != nil {
			out = append(out, v.Name)
		}
	}
	return out
}

func presentBlocklist(st *model.State, b *model.Blocklist, status *model.BlocklistStatus) api.Blocklist {
	views := st.BlockingViews(b.ViewIDs)
	out := api.Blocklist{Blocklist: *b, Views: viewNames(st, views), AutoViews: len(b.ViewIDs) == 0 && len(st.Views) > 0, Status: status}
	switch {
	case b.Disabled:
		out.State = "disabled"
	case len(views) == 0:
		out.State = "idle"
	case status != nil && status.Error != "":
		out.State = "error"
	case status == nil || status.UpdatedAt == nil:
		out.State = "waiting"
	default:
		out.State = "ok"
	}
	if status != nil && !b.Disabled {
		out.MemoryMB = int((int64(status.Records)*bytesPerRecord*int64(len(views)) + 1<<19) >> 20)
	}
	return out
}

func presentBlockRule(st *model.State, r *model.BlockRule) api.BlockRule {
	return api.BlockRule{BlockRule: *r, Views: viewNames(st, st.BlockingViews(r.ViewIDs)), AutoViews: len(r.ViewIDs) == 0 && len(st.Views) > 0}
}

func requireBlocking(p *auth.Principal) error {
	return require(p, auth.Action{Resource: auth.ResBlocking})
}

func (s *Server) listBlocklists(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if err := requireBlocking(p); err != nil {
		return err
	}
	st, base, err := s.states(r)
	if err != nil {
		return err
	}
	statuses, err := s.store.BlocklistStatuses(r.Context())
	if err != nil {
		return err
	}
	out := []api.Blocklist{}
	for _, b := range st.SortedBlocklists() {
		o := presentBlocklist(st, b, statuses[b.ID])
		o.Pending = pending(base, base != nil && base.Blocklists[b.ID] == nil, base != nil && base.Blocklists[b.ID] != nil && base.Blocklists[b.ID].Version != b.Version)
		out = append(out, o)
	}
	if base != nil {
		for _, b := range base.SortedBlocklists() {
			if st.Blocklists[b.ID] == nil {
				o := presentBlocklist(base, b, statuses[b.ID])
				o.Pending = "delete"
				out = append(out, o)
			}
		}
	}
	writeJSON(w, http.StatusOK, out)
	return nil
}

// pending returns the pending marker of an object listed with a changeset.
func pending(base *model.State, added, changed bool) string {
	switch {
	case base == nil:
		return ""
	case added:
		return "add"
	case changed:
		return "change"
	}
	return ""
}

func (s *Server) blocklistByPath(r *http.Request, st *model.State) (*model.Blocklist, error) {
	ref := r.PathValue("id")
	var b *model.Blocklist
	if id, err := strconv.ParseInt(ref, 10, 64); err == nil {
		b = st.Blocklists[id]
	} else {
		b = st.BlocklistByName(ref)
	}
	if b == nil {
		return nil, notFound("blocklist %s not found", ref)
	}
	return b, nil
}

func (s *Server) blocklistObject(ctx context.Context) func(*model.State, int64) any {
	return func(st *model.State, id int64) any {
		b := st.Blocklists[id]
		if b == nil {
			return nil
		}
		statuses, _ := s.store.BlocklistStatuses(ctx)
		return presentBlocklist(st, b, statuses[id])
	}
}

func (s *Server) getBlocklist(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if err := requireBlocking(p); err != nil {
		return err
	}
	st, err := s.state(r)
	if err != nil {
		return err
	}
	b, err := s.blocklistByPath(r, st)
	if err != nil {
		return err
	}
	writeJSON(w, http.StatusOK, s.blocklistObject(r.Context())(st, b.ID))
	return nil
}

func (s *Server) createBlocklist(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	body, err := readBody(r)
	if err != nil {
		return err
	}
	return s.mutate(w, r, p, "", []engine.Request{request(engine.OpBlocklistCreate, 0, body)}, s.blocklistObject(r.Context()))
}

func (s *Server) updateBlocklist(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	st, err := s.state(r)
	if err != nil {
		return err
	}
	b, err := s.blocklistByPath(r, st)
	if err != nil {
		return err
	}
	body, err := readBody(r)
	if err != nil {
		return err
	}
	id := b.ID
	return s.mutate(w, r, p, "", []engine.Request{request(engine.OpBlocklistUpdate, id, body)}, func(st *model.State, _ int64) any { return s.blocklistObject(r.Context())(st, id) })
}

func (s *Server) deleteBlocklist(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	st, err := s.state(r)
	if err != nil {
		return err
	}
	b, err := s.blocklistByPath(r, st)
	if err != nil {
		return err
	}
	return s.mutate(w, r, p, "", []engine.Request{request(engine.OpBlocklistDelete, b.ID, nil)}, nil)
}

// refreshBlocklist: POST /blocking/lists/{id}/refresh[?force=1] downloads
// the list now and waits for the result.
func (s *Server) refreshBlocklist(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if err := require(p, auth.Action{Resource: auth.ResBlocking, Write: true}); err != nil {
		return err
	}
	st, err := s.store.LoadState(r.Context())
	if err != nil {
		return err
	}
	b, err := s.blocklistByPath(r, st)
	if err != nil {
		return err
	}
	ctx, cancel := context.WithTimeout(r.Context(), 3*time.Minute)
	defer cancel()
	status, rerr := s.eng.RefreshBlocklist(ctx, b.ID, queryBool(r, "force"))
	if status == nil {
		return rerr
	}
	writeJSON(w, http.StatusOK, presentBlocklist(st, b, status))
	return nil
}

func (s *Server) listBlockRules(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if err := requireBlocking(p); err != nil {
		return err
	}
	st, base, err := s.states(r)
	if err != nil {
		return err
	}
	out := []api.BlockRule{}
	for _, rule := range st.SortedBlockRules() {
		o := presentBlockRule(st, rule)
		o.Pending = pending(base, base != nil && base.BlockRules[rule.ID] == nil, base != nil && base.BlockRules[rule.ID] != nil && base.BlockRules[rule.ID].Version != rule.Version)
		out = append(out, o)
	}
	if base != nil {
		for _, rule := range base.SortedBlockRules() {
			if st.BlockRules[rule.ID] == nil {
				o := presentBlockRule(base, rule)
				o.Pending = "delete"
				out = append(out, o)
			}
		}
	}
	writeJSON(w, http.StatusOK, out)
	return nil
}

func ruleObject(st *model.State, id int64) any {
	if rule := st.BlockRules[id]; rule != nil {
		return presentBlockRule(st, rule)
	}
	return nil
}

func (s *Server) ruleByPath(r *http.Request, st *model.State) (*model.BlockRule, error) {
	id, _ := strconv.ParseInt(r.PathValue("id"), 10, 64)
	rule := st.BlockRules[id]
	if rule == nil {
		return nil, notFound("rule %s not found", r.PathValue("id"))
	}
	return rule, nil
}

func (s *Server) createBlockRule(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	body, err := readBody(r)
	if err != nil {
		return err
	}
	return s.mutate(w, r, p, "", []engine.Request{request(engine.OpBlockRuleCreate, 0, body)}, ruleObject)
}

func (s *Server) updateBlockRule(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	st, err := s.state(r)
	if err != nil {
		return err
	}
	rule, err := s.ruleByPath(r, st)
	if err != nil {
		return err
	}
	body, err := readBody(r)
	if err != nil {
		return err
	}
	id := rule.ID
	return s.mutate(w, r, p, "", []engine.Request{request(engine.OpBlockRuleUpdate, id, body)}, func(st *model.State, _ int64) any { return ruleObject(st, id) })
}

func (s *Server) deleteBlockRule(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	st, err := s.state(r)
	if err != nil {
		return err
	}
	rule, err := s.ruleByPath(r, st)
	if err != nil {
		return err
	}
	return s.mutate(w, r, p, "", []engine.Request{request(engine.OpBlockRuleDelete, rule.ID, nil)}, nil)
}

// deleteBlockRulesByName: DELETE /blocking/rules?name=NAME[&view=VIEW]
// deletes the rules for a domain (in one view, or all).
func (s *Server) deleteBlockRulesByName(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	st, err := s.state(r)
	if err != nil {
		return err
	}
	q := r.URL.Query()
	name := strings.TrimSuffix(strings.ToLower(strings.TrimSpace(q.Get("name"))), ".")
	if name == "" {
		return badRequest("give the domain of the rules to delete (name=)")
	}
	var viewID int64 = -1
	if vn := q.Get("view"); vn != "" {
		v := st.ViewByName(vn)
		if v == nil {
			return notFound("view %s not found", vn)
		}
		viewID = v.ID
	}
	var reqs []engine.Request
	for _, rule := range st.SortedBlockRules() {
		if rule.Name != name {
			continue
		}
		if viewID >= 0 && !slices.Contains(st.BlockingViews(rule.ViewIDs), viewID) {
			continue
		}
		reqs = append(reqs, request(engine.OpBlockRuleDelete, rule.ID, nil))
	}
	if len(reqs) == 0 {
		if queryBool(r, "missing_ok") {
			writeJSON(w, http.StatusOK, api.MutationResponse{})
			return nil
		}
		return notFound("there is no rule for %s", name)
	}
	return s.mutate(w, r, p, "", reqs, nil)
}

// checkBlocking: GET /blocking/check?name=NAME says what blocking does
// with a name in each view.
func (s *Server) checkBlocking(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if err := requireBlocking(p); err != nil {
		return err
	}
	st, err := s.store.LoadState(r.Context())
	if err != nil {
		return err
	}
	out, err := s.eng.CheckBlocking(st, r.URL.Query().Get("name"))
	if err != nil {
		return err
	}
	if out == nil {
		out = []blocking.Match{}
	}
	writeJSON(w, http.StatusOK, out)
	return nil
}

// blocklistErrors lists the enabled blocklists whose last update failed,
// for the dashboard.
func (s *Server) blocklistErrors(ctx context.Context) []api.BlocklistError {
	st, err := s.store.LoadState(ctx)
	if err != nil || len(st.Blocklists) == 0 {
		return nil
	}
	statuses, err := s.store.BlocklistStatuses(ctx)
	if err != nil {
		return nil
	}
	var out []api.BlocklistError
	for _, b := range st.SortedBlocklists() {
		if s := statuses[b.ID]; s != nil && s.Error != "" && !b.Disabled {
			out = append(out, api.BlocklistError{Name: b.Name, Error: s.Error, UpdatedAt: s.UpdatedAt})
		}
	}
	return out
}

// blockingStatus: GET /blocking/status says whether blocking is paused.
func (s *Server) blockingStatus(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if err := requireBlocking(p); err != nil {
		return err
	}
	st, err := s.store.LoadState(r.Context())
	if err != nil {
		return err
	}
	writeJSON(w, http.StatusOK, map[string]any{"paused_until": st.Settings.BlockingPausedUntil})
	return nil
}

// pauseBlocking: POST /blocking/pause {"minutes": 10} lets every name
// through until then; POST /blocking/resume ends it.
func (s *Server) pauseBlocking(resume bool) func(http.ResponseWriter, *http.Request, *auth.Principal) error {
	return func(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
		var in engine.BlockingPauseInput
		if !resume {
			var body struct {
				Minutes int `json:"minutes"`
			}
			if err := decodeJSON(r, &body); err != nil {
				return err
			}
			if body.Minutes < 1 || time.Duration(body.Minutes)*time.Minute > engine.MaxBlockingPause {
				return badRequest("pause for 1 to %d minutes", int(engine.MaxBlockingPause/time.Minute))
			}
			until := time.Now().Add(time.Duration(body.Minutes) * time.Minute).Truncate(time.Second)
			in.Until = &until
		}
		return s.mutate(w, r, p, "", []engine.Request{engine.NewRequest(engine.OpBlockingPause, 0, in)}, nil)
	}
}