package server

import (
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"strings"
	"time"

	"github.com/Autumn-27/artex/db"
	"github.com/Autumn-27/artex/notify"
)

// This file is the HTTP API for the notification delivery feature. All routes are
// mounted behind requireAuth (see Handler()), consistent with the other admin APIs.

// notifyChannelDTO is the external representation of a channel.
//
// Config is the **masked** configuration: credential fields are replaced with
// values prefixed by notify.MaskedPrefix. The frontend submitting a masked value
// back unchanged means "this field was not modified", and the server keeps the
// original value in the database accordingly (see notify.MergeConfig).
type notifyChannelDTO struct {
	ID         int64          `json:"id"`
	Name       string         `json:"name"`
	Kind       string         `json:"kind"`
	Enabled    bool           `json:"enabled"`
	Mode       string         `json:"mode"`
	Config     map[string]any `json:"config"`
	Filter     notify.Filter  `json:"filter"`
	RatePerMin int            `json:"rate_per_min"`
	CreatedAt  time.Time      `json:"created_at"`
	UpdatedAt  time.Time      `json:"updated_at"`
	// SecretKeys tells the frontend which fields are credentials, so it can render
	// password inputs and a "leave empty to keep unchanged" hint. Declared by the
	// channel itself (notify.Channel.SecretKeys); the frontend hardcodes no
	// channel-specific knowledge.
	SecretKeys []string `json:"secret_keys"`
}

// notifyDeliveryDTO is the external representation of a delivery history entry.
type notifyDeliveryDTO struct {
	ID          int64      `json:"id"`
	FindingID   int64      `json:"finding_id,string"`
	EventKind   string     `json:"event_kind"`
	ChannelID   int64      `json:"channel_id"`
	ChannelName string     `json:"channel_name"`
	ChannelKind string     `json:"channel_kind"`
	State       string     `json:"state"`
	Attempts    int        `json:"attempts"`
	LastError   string     `json:"last_error"`
	BatchID     *int64     `json:"batch_id,omitempty"`
	CreatedAt   time.Time  `json:"created_at"`
	SentAt      *time.Time `json:"sent_at,omitempty"`
	NextAttempt time.Time  `json:"next_attempt_at"`
	// Message title digest, so the history list can show what this delivery is
	// about without expanding it.
	Title    string `json:"title"`
	Severity string `json:"severity"`
}

func toNotifyChannelDTO(ch *db.NotificationChannel) notifyChannelDTO {
	var cfg map[string]any
	if len(ch.Config) > 0 {
		_ = json.Unmarshal(ch.Config, &cfg)
	}
	if cfg == nil {
		cfg = map[string]any{}
	}
	secrets := []string{}
	if c, ok := notify.Get(ch.Kind); ok {
		secrets = c.SecretKeys()
	}
	return notifyChannelDTO{
		ID:         ch.ID,
		Name:       ch.Name,
		Kind:       ch.Kind,
		Enabled:    ch.IsEnabled(),
		Mode:       ch.Mode,
		Config:     notify.MaskConfig(ch.Kind, cfg),
		Filter:     notify.ParseFilter(ch.Filter),
		RatePerMin: ch.RatePerMin,
		CreatedAt:  ch.CreatedAt,
		UpdatedAt:  ch.UpdatedAt,
		SecretKeys: secrets,
	}
}

func toNotifyDeliveryDTO(dl *db.NotificationDelivery) notifyDeliveryDTO {
	snap, _ := parseSnapshot(dl)
	dto := notifyDeliveryDTO{
		ID:          dl.ID,
		FindingID:   dl.FindingID,
		EventKind:   dl.EventKind,
		ChannelID:   dl.ChannelID,
		ChannelName: dl.ChannelName,
		ChannelKind: dl.ChannelKind,
		State:       dl.State,
		Attempts:    dl.Attempts,
		LastError:   dl.LastError,
		BatchID:     dl.BatchID,
		CreatedAt:   dl.CreatedAt,
		SentAt:      dl.SentAt,
		NextAttempt: dl.NextAttemptAt,
		Severity:    snap.Severity,
	}
	if snap.Name != "" {
		dto.Title = snap.Name
	} else {
		dto.Title = snap.VulnClass
	}
	return dto
}

// notifyMeta returns the static metadata and global settings the notification
// page needs, all in one request, so the frontend does not have to fire three
// requests just to render a dropdown.
func (s *Server) notifyMeta(w http.ResponseWriter, r *http.Request) {
	pg := s.pg(w)
	if pg == nil {
		return
	}
	kinds := make([]map[string]any, 0, len(notify.Kinds()))
	for _, k := range notify.Kinds() {
		ch, _ := notify.Get(k)
		kinds = append(kinds, map[string]any{
			"kind":                 k,
			"default_rate_per_min": ch.DefaultRatePerMin(),
			"secret_keys":          ch.SecretKeys(),
		})
	}
	baseURL, _, _ := pg.GetSetting(settingNotifyPublicBaseURL)
	digest, _, _ := pg.GetSetting(settingNotifyDigestMinutes)
	stats, err := pg.NotificationStatsSnapshot(r.Context())
	if err != nil {
		writeErr(w, 500, err.Error())
		return
	}
	writeJSON(w, 200, map[string]any{
		"kinds":               kinds,
		"enabled":             pg.GetBool(settingNotifyEnabled, true),
		"public_base_url":     baseURL,
		"digest_interval_min": digest,
		"defaults": map[string]any{
			"digest_interval_min": notifyDefaultDigestMinutes,
		},
		"stats": stats,
	})
}

func (s *Server) notifyListChannels(w http.ResponseWriter, r *http.Request) {
	pg := s.pg(w)
	if pg == nil {
		return
	}
	channels, err := pg.ListNotificationChannels(r.Context())
	if err != nil {
		writeErr(w, 500, err.Error())
		return
	}
	out := make([]notifyChannelDTO, 0, len(channels))
	for _, ch := range channels {
		out = append(out, toNotifyChannelDTO(ch))
	}
	writeJSON(w, 200, map[string]any{"channels": out})
}

// notifyChannelRequest is the request body for creating/updating a channel.
//
// All business fields are pointers, so that "not sent" can be told apart from
// "sent as zero value": under PATCH semantics, fields that were not sent must
// keep their original values in the database.
type notifyChannelRequest struct {
	Name       *string        `json:"name"`
	Kind       *string        `json:"kind"`
	Enabled    *bool          `json:"enabled"`
	Mode       *string        `json:"mode"`
	Config     map[string]any `json:"config"`
	Filter     *notify.Filter `json:"filter"`
	RatePerMin *int           `json:"rate_per_min"`
}

func (s *Server) notifyCreateChannel(w http.ResponseWriter, r *http.Request) {
	pg := s.pg(w)
	if pg == nil {
		return
	}
	var req notifyChannelRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeErr(w, 400, "request body is not valid JSON: "+err.Error())
		return
	}
	if req.Kind == nil || !notify.ValidKind(*req.Kind) {
		writeErr(w, 400, fmt.Sprintf("invalid channel type, available: %s", strings.Join(notify.Kinds(), " / ")))
		return
	}
	name := ""
	if req.Name != nil {
		name = strings.TrimSpace(*req.Name)
	}
	if name == "" {
		writeErr(w, 400, "channel name is required")
		return
	}
	channel, _ := notify.Get(*req.Kind)
	if err := channel.Validate(req.Config); err != nil {
		writeErr(w, 400, err.Error())
		return
	}
	ch := &db.NotificationChannel{
		Name:       name,
		Kind:       *req.Kind,
		Enabled:    req.Enabled,
		Mode:       db.NotifyModeRealtime,
		RatePerMin: channel.DefaultRatePerMin(),
	}
	if req.Mode != nil {
		if !db.ValidNotifyMode(*req.Mode) {
			writeErr(w, 400, "invalid delivery mode, available: realtime / digest")
			return
		}
		ch.Mode = *req.Mode
	}
	if req.RatePerMin != nil {
		// Use the explicitly given value as-is — including 0, which means
		// "no rate limit" and is a valid configuration.
		if *req.RatePerMin < 0 {
			writeErr(w, 400, "rate limit must not be negative")
			return
		}
		ch.RatePerMin = *req.RatePerMin
	}
	// Only apply the channel default when the field is absent. The default must be
	// decided here rather than in the db layer: only the request body can
	// distinguish "this field was not sent" from "explicitly sent 0", and the two
	// mean entirely different things (former = use default, latter = no rate
	// limit). If the db layer also treated 0 as unspecified, the no-rate-limit
	// configuration would be unreachable.
	if req.RatePerMin == nil {
		ch.RatePerMin = channel.DefaultRatePerMin()
	}
	if req.Filter != nil {
		// Validate restricted-value filter fields (e.g. min_severity) on write. See
		// notify.Filter.Validate for details: a typo in the threshold would
		// silently disable the filter into delivering everything, so it must be
		// blocked at the entry point.
		if err := req.Filter.Validate(); err != nil {
			writeErr(w, 400, err.Error())
			return
		}
		raw, _ := json.Marshal(req.Filter)
		ch.Filter = raw
	}
	rawCfg, _ := json.Marshal(req.Config)
	ch.Config = rawCfg

	id, err := pg.SaveNotificationChannel(r.Context(), ch)
	if err != nil {
		writeErr(w, 500, err.Error())
		return
	}
	writeJSON(w, 200, map[string]any{"id": id})
}

func (s *Server) notifyUpdateChannel(w http.ResponseWriter, r *http.Request) {
	pg := s.pg(w)
	if pg == nil {
		return
	}
	id, ok := pathInt(r, "id")
	if !ok {
		writeErr(w, 400, "invalid channel id")
		return
	}
	current, err := pg.NotificationChannelByID(r.Context(), id)
	if err != nil {
		notifyChannelLookupErr(w, err)
		return
	}
	var req notifyChannelRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeErr(w, 400, "request body is not valid JSON: "+err.Error())
		return
	}

	// kind may be changed, but changing the type means the whole set of credential
	// fields is replaced and cannot be merged with the old config.
	kind := current.Kind
	if req.Kind != nil {
		if !notify.ValidKind(*req.Kind) {
			writeErr(w, 400, fmt.Sprintf("invalid channel type, available: %s", strings.Join(notify.Kinds(), " / ")))
			return
		}
		kind = *req.Kind
	}
	channel, _ := notify.Get(kind)

	var stored map[string]any
	if kind == current.Kind {
		if len(current.Config) > 0 {
			_ = json.Unmarshal(current.Config, &stored)
		}
	}
	if stored == nil {
		stored = map[string]any{}
	}
	// Use PrepareConfigUpdate rather than bare MergeConfig: when the target address
	// changes, the operator must re-affirm the credential fields, otherwise
	// "change the address only, keep the credentials" would send the real
	// credentials from the database to the new address.
	merged, err := notify.PrepareConfigUpdate(kind, stored, req.Config)
	if err != nil {
		writeErr(w, 400, err.Error())
		return
	}
	if err := channel.Validate(merged); err != nil {
		writeErr(w, 400, err.Error())
		return
	}
	rawCfg, _ := json.Marshal(merged)

	ch := &db.NotificationChannel{
		ID:         id,
		Name:       current.Name,
		Kind:       kind,
		Enabled:    current.Enabled,
		Mode:       current.Mode,
		Config:     rawCfg,
		Filter:     current.Filter,
		RatePerMin: current.RatePerMin,
	}
	if req.Name != nil {
		if ch.Name = strings.TrimSpace(*req.Name); ch.Name == "" {
			writeErr(w, 400, "channel name must not be empty")
			return
		}
	}
	if req.Enabled != nil {
		ch.Enabled = req.Enabled
	}
	if req.Mode != nil {
		if !db.ValidNotifyMode(*req.Mode) {
			writeErr(w, 400, "invalid delivery mode, available: realtime / digest")
			return
		}
		ch.Mode = *req.Mode
	}
	if req.RatePerMin != nil {
		if *req.RatePerMin < 0 {
			writeErr(w, 400, "rate limit must not be negative")
			return
		}
		ch.RatePerMin = *req.RatePerMin
	}
	if req.Filter != nil {
		if err := req.Filter.Validate(); err != nil {
			writeErr(w, 400, err.Error())
			return
		}
		raw, _ := json.Marshal(req.Filter)
		ch.Filter = raw
	}

	// Going through SetNotificationChannelEnabled instead of the plain
	// SaveNotificationChannel path ensures that "disabling" also marks pending
	// deliveries as skipped, so re-enabling does not deliver a batch of stale,
	// backlogged messages.
	enabledChanged := ch.Enabled != nil && current.Enabled != nil && *ch.Enabled != *current.Enabled
	if enabledChanged {
		// Persist the config update first (with enabled kept at the old value, so
		// the skip logic is not triggered prematurely), then flip the switch
		// separately. There is no concurrency window between the two steps: this
		// endpoint is the only entry point that modifies these two fields.
		prev := ch.Enabled
		ch.Enabled = current.Enabled
		if _, err := pg.SaveNotificationChannel(r.Context(), ch); err != nil {
			writeErr(w, 500, err.Error())
			return
		}
		if err := pg.SetNotificationChannelEnabled(r.Context(), id, *prev); err != nil {
			writeErr(w, 500, err.Error())
			return
		}
		writeJSON(w, 200, map[string]any{"id": id})
		return
	}
	if _, err := pg.SaveNotificationChannel(r.Context(), ch); err != nil {
		writeErr(w, 500, err.Error())
		return
	}
	writeJSON(w, 200, map[string]any{"id": id})
}

func (s *Server) notifyDeleteChannel(w http.ResponseWriter, r *http.Request) {
	pg := s.pg(w)
	if pg == nil {
		return
	}
	id, ok := pathInt(r, "id")
	if !ok {
		writeErr(w, 400, "invalid channel id")
		return
	}
	if err := pg.DeleteNotificationChannel(r.Context(), id); err != nil {
		notifyChannelLookupErr(w, err)
		return
	}
	writeJSON(w, 200, map[string]any{"ok": true})
}

// notifyTestChannel sends one test message with the currently saved
// configuration.
//
// It calls the channel's Send directly, bypassing the delivery queue: the point
// of the test is to tell the user immediately "whether this configuration can
// deliver"; going through the queue would hide the result inside the delivery
// history, forcing the user to dig it up to know whether it worked. This
// endpoint is therefore **synchronous**, with the timeout bounded by the notify
// package's HTTP client (15 seconds).
func (s *Server) notifyTestChannel(w http.ResponseWriter, r *http.Request) {
	pg := s.pg(w)
	if pg == nil {
		return
	}
	id, ok := pathInt(r, "id")
	if !ok {
		writeErr(w, 400, "invalid channel id")
		return
	}
	ch, err := pg.NotificationChannelByID(r.Context(), id)
	if err != nil {
		notifyChannelLookupErr(w, err)
		return
	}
	channel, ok := notify.Get(ch.Kind)
	if !ok {
		writeErr(w, 400, fmt.Sprintf("channel type %q is not registered", ch.Kind))
		return
	}
	var cfg map[string]any
	if len(ch.Config) > 0 {
		_ = json.Unmarshal(ch.Config, &cfg)
	}
	if err := channel.Validate(cfg); err != nil {
		writeErr(w, 400, err.Error())
		return
	}
	msg := notifyTestMessage(s.notifierBaseURL(pg))
	start := time.Now()
	// The test message is a single entry, so the delivered count is not needed
	// here (for a single message the channel length limit falls back to
	// truncation; no segmentation is involved).
	if _, err := channel.Send(r.Context(), cfg, msg); err != nil {
		// Return the channel's raw error to the user as-is — it is their only clue
		// when debugging the configuration.
		writeErr(w, 502, err.Error())
		return
	}
	writeJSON(w, 200, map[string]any{
		"ok":         true,
		"latency_ms": time.Since(start).Milliseconds(),
	})
}

// notifyTestMessage builds the test message. Its content is deliberately
// recognizable as a test at a glance: recipients should not mistake it for a
// real vulnerability.
func notifyTestMessage(baseURL string) notify.Message {
	return notify.Message{
		Items: []notify.Item{{
			FindingID: 0,
			Name:      "Test message · channel configuration OK",
			VulnClass: "Connectivity test",
			Severity:  "low",
			Summary:   "This is a test message for an ARTEX notification channel; receiving it means the channel is configured correctly.",
			Assets:    []string{"artex.example.com"},
			DetailURL: baseURL,
		}},
		HomeURL: baseURL,
	}
}

// notifierBaseURL reads the external address used for back-links.
func (s *Server) notifierBaseURL(pg *db.DB) string {
	v, _, _ := pg.GetSetting(settingNotifyPublicBaseURL)
	return trimTrailingSlash(v)
}

func (s *Server) notifyListDeliveries(w http.ResponseWriter, r *http.Request) {
	pg := s.pg(w)
	if pg == nil {
		return
	}
	f := db.NotificationDeliveryFilter{
		State:     r.URL.Query().Get("state"),
		EventKind: r.URL.Query().Get("event_kind"),
	}
	if v := r.URL.Query().Get("channel_id"); v != "" {
		f.ChannelID = int64(atoiDefault(v, 0))
	}
	page := queryInt(r, "page", 1)
	pageSize := queryInt(r, "page_size", 50)
	items, total, err := pg.ListNotificationDeliveries(r.Context(), f, page, pageSize)
	if err != nil {
		writeErr(w, 500, err.Error())
		return
	}
	out := make([]notifyDeliveryDTO, 0, len(items))
	for _, dl := range items {
		out = append(out, toNotifyDeliveryDTO(dl))
	}
	writeJSON(w, 200, map[string]any{"deliveries": out, "total": total, "page": page, "page_size": pageSize})
}

func (s *Server) notifyRetryDelivery(w http.ResponseWriter, r *http.Request) {
	pg := s.pg(w)
	if pg == nil {
		return
	}
	id, ok := pathInt(r, "id")
	if !ok {
		writeErr(w, 400, "invalid delivery id")
		return
	}
	if err := pg.RetryNotificationDelivery(r.Context(), id); err != nil {
		writeErr(w, 400, err.Error())
		return
	}
	writeJSON(w, 200, map[string]any{"ok": true})
}

// notifyChannelLookupErr translates "channel does not exist" into 404, all other
// errors into 500.
func notifyChannelLookupErr(w http.ResponseWriter, err error) {
	if errors.Is(err, db.ErrNotificationChannelNotFound) {
		writeErr(w, 404, "notification channel does not exist")
		return
	}
	writeErr(w, 500, err.Error())
}