package main

import (
	"context"
	"errors"
	"net"
	"net/http"
	"strconv"
	"strings"
	"sync/atomic"
	"time"
	"unicode/utf8"

	"github.com/jkaninda/okapi"
)

// Handler holds the dependencies for the HTTP layer.
type Handler struct {
	store    *Store
	broker   *Broker
	auth     *AdminAuth
	appName  string
	version  string
	host     string
	dbDriver string
	debug    bool
	started  time.Time

	unhealthy atomic.Bool
	chaos     chaosState
	// requests counts HTTP requests answered by this replica since boot. A
	// rolling update resets it one container at a time; see countRequests.
	requests atomic.Int64
}

// serverTime is the shape of the live clock payload (v2 feature). It carries
// the version and host so a canary viewer can see exactly which build/replica
// answered.
func (h *Handler) serverTime() okapi.M {
	return okapi.M{
		"time":    time.Now().Format(time.RFC3339),
		"version": h.version,
		"host":    h.host,
	}
}

// createEntryRequest is the POST /api/entries body.
type createEntryRequest struct {
	Name    string `json:"name"`
	Message string `json:"message"`
}

const (
	maxNameLen    = 60
	maxMessageLen = 500
)

// Health reports liveness/readiness. Returns 503 when the database is
// unreachable so Miabi's health checks hold traffic until the DB is up.
func (h *Handler) Health(c *okapi.Context) error {
	if h.unhealthy.Load() {
		return c.JSON(http.StatusServiceUnavailable, okapi.M{
			"status":  "unavailable",
			"reason":  "forced unhealthy via /api/debug/health",
			"version": h.version,
			"host":    h.host,
		})
	}
	if err := h.store.Ping(c.Request().Context()); err != nil {
		return c.JSON(http.StatusServiceUnavailable, okapi.M{
			"status":  "unavailable",
			"db":      "down",
			"version": h.version,
		})
	}
	return c.OK(okapi.M{
		"status":   "ok",
		"db":       "up",
		"redis":    h.broker.RedisStatus(c.Request().Context()),
		"app":      h.appName,
		"version":  h.version,
		"host":     h.host,
		"requests": h.requests.Load(),
	})
}

// Info returns app metadata for the UI: name, the serving version (useful for
// spotting which build answered during a canary rollout), and how many clients
// are currently connected.
func (h *Handler) Info(c *okapi.Context) error {
	return c.OK(okapi.M{
		"app":       h.appName,
		"version":   h.version,
		"online":    h.broker.Online(),
		"host":      h.host,
		"broker":    h.broker.Mode(),
		"replicas":  h.broker.Replicas(),
		"requests":  h.requests.Load(),
		"admin":     h.auth.Enabled(),
		"reactions": ReactionEmojis(),
		"visitors":  h.visitorsActive(c.Request().Context()),
	})
}

// visitorsActive counts identities seen in the last few minutes — the
// "currently visiting" number. It degrades to 0 on a database hiccup; the
// SSE presence event simply carries whatever the database last said.
func (h *Handler) visitorsActive(ctx context.Context) int64 {
	n, err := h.store.VisitorsSeenAfter(ctx, time.Now().Add(-visitorFreshWindow))
	if err != nil {
		return 0
	}
	return n
}

// PublicSettings returns the wall state visitors need: paused flag and banner.
func (h *Handler) PublicSettings(c *okapi.Context) error {
	st, err := h.store.Settings(c.Request().Context())
	if err != nil {
		return c.JSON(http.StatusInternalServerError, okapi.M{"error": "could not load settings"})
	}
	return c.OK(st)
}

// Time returns the current server time (plus version + host). Handy for probing
// a canary rollout from the shell: `watch curl -s .../api/time`.
func (h *Handler) Time(c *okapi.Context) error {
	return c.OK(h.serverTime())
}

// ListEntries returns visible entries, pinned first, with simple pagination.
// Query params: limit (default 100, max 200) and offset (default 0). The home
// page requests a small limit; the "All signatures" page pages through them.
func (h *Handler) ListEntries(c *okapi.Context) error {
	ctx := c.Request().Context()

	limit := atoiDefault(c.Query("limit"), 100)
	if limit <= 0 || limit > 200 {
		limit = 100
	}
	offset := atoiDefault(c.Query("offset"), 0)
	if offset < 0 {
		offset = 0
	}

	entries, err := h.store.List(ctx, limit, offset)
	if err != nil {
		return c.JSON(http.StatusInternalServerError, okapi.M{"error": "could not load entries"})
	}
	count, _ := h.store.CountVisible(ctx)
	return c.OK(okapi.M{
		"entries": entries,
		"total":   count,
		"limit":   limit,
		"offset":  offset,
	})
}

// atoiDefault parses s as an int, returning def when empty or invalid.
func atoiDefault(s string, def int) int {
	if s == "" {
		return def
	}
	n, err := strconv.Atoi(s)
	if err != nil {
		return def
	}
	return n
}

// CreateEntry adds a new signature to the wall and broadcasts it live.
func (h *Handler) CreateEntry(c *okapi.Context) error {
	ctx := c.Request().Context()
	// Read from the DB rather than a cache so a pause applies on every replica.
	if st, err := h.store.Settings(ctx); err == nil && st.SigningPaused {
		return c.JSON(http.StatusServiceUnavailable, okapi.M{"error": "signing is paused by a moderator"})
	}

	var req createEntryRequest
	if err := c.Bind(&req); err != nil {
		return c.JSON(http.StatusBadRequest, okapi.M{"error": "invalid JSON body"})
	}

	name := strings.TrimSpace(req.Name)
	message := strings.TrimSpace(req.Message)

	if r := []rune(name); len(r) > maxNameLen {
		name = string(r[:maxNameLen])
	}
	if message == "" {
		return c.JSON(http.StatusBadRequest, okapi.M{"error": "message is required"})
	}
	if utf8.RuneCountInString(message) > maxMessageLen {
		return c.JSON(http.StatusBadRequest, okapi.M{
			"error": "message is too long (max 500 characters)",
		})
	}

	// The visitor identity ties the signature to a browser: an unsigned post
	// keeps the name the visitor used before, and a signed post is remembered
	// for next time.
	visitor := visitorFromContext(c)
	if name == "" {
		name = visitorName(visitor)
	}
	if name == "" {
		name = "Anonymous"
	}

	entry, err := h.store.Create(ctx, name, message, h.host, clientIP(c))
	if err != nil {
		return c.JSON(http.StatusInternalServerError, okapi.M{"error": "could not save entry"})
	}
	if !visitor.IsZero() {
		h.store.VisitorSigned(ctx, visitor.ID, name)
	}

	h.broker.Publish(Event{Type: "created", Entry: &entry})
	return c.Created(entry)
}

// DeleteEntry soft-deletes an entry by id and broadcasts the removal live.
func (h *Handler) DeleteEntry(c *okapi.Context) error {
	id, err := strconv.ParseUint(c.Param("id"), 10, 64)
	if err != nil {
		return c.JSON(http.StatusBadRequest, okapi.M{"error": "invalid id"})
	}
	ok, err := h.store.Delete(c.Request().Context(), id)
	if err != nil {
		return c.JSON(http.StatusInternalServerError, okapi.M{"error": "could not delete entry"})
	}
	if !ok {
		return c.JSON(http.StatusNotFound, okapi.M{"error": "entry not found"})
	}

	h.broker.Publish(Event{Type: "deleted", ID: uint(id)})
	return c.NoContent()
}

// Stream is the SSE endpoint. Each client subscribes to the broker and receives
// live "created" / "deleted" / "presence" events. A "welcome" event is sent
// first so the client immediately knows the serving version and online count.
func (h *Handler) Stream(c *okapi.Context) error {
	ctx, cancel := context.WithCancel(c.Request().Context())
	defer cancel()

	subscription := h.broker.Subscribe()
	defer h.broker.Unsubscribe(subscription)

	msgs := make(chan okapi.Message, 32)
	go func() {
		defer close(msgs)

		welcome := okapi.Message{Event: "welcome", Data: okapi.M{
			"version":  h.version,
			"online":   h.broker.Online(),
			"replicas": len(h.broker.Replicas()),
			"host":     h.host,
			"visitors": h.visitorsActive(ctx),
		}}
		select {
		case msgs <- welcome:
		case <-ctx.Done():
			return
		}

		for {
			select {
			case <-ctx.Done():
				return
			case ev, ok := <-subscription:
				if !ok {
					return
				}
				select {
				case msgs <- okapi.Message{Event: ev.Type, Data: ev}:
				case <-ctx.Done():
					return
				}
			}
		}
	}()

	err := c.SSEStreamWithOptions(ctx, msgs, &okapi.StreamOptions{
		Serializer:   &okapi.JSONSerializer{},
		PingInterval: 25 * time.Second,
	})
	// A client closing the stream is how every SSE session ends, not a failure.
	if errors.Is(err, context.Canceled) {
		return nil
	}
	return err
}

// clientIP returns the caller's address as seen through the gateway. Without
// TRUSTED_PROXIES the forwarded headers are taken at face value, which is
// fine for display but spoofable.
func clientIP(c *okapi.Context) string {
	if ip := c.RealIP(); net.ParseIP(ip) != nil {
		return ip
	}
	if host, _, err := net.SplitHostPort(c.Request().RemoteAddr); err == nil {
		return host
	}
	return ""
}