package api

import (
	"database/sql"
	"fmt"
	"net/http"
	"strconv"
	"strings"
	"time"

	"git.ryuvia.com/niklas/terdut-server/internal/models"
	"github.com/go-chi/chi/v5"
)

func handleListIncidents(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		q := r.URL.Query()

		where := []string{}
		args := &sqlArgs{}

		// Without an explicit status the queue shows open work, which is what an
		// on-call person opens the tool to see.
		if status := q.Get("status"); status != "" {
			where = append(where, "i.status = "+args.add(status))
		} else {
			where = append(where, "i.resolved_at IS NULL")
		}

		if q.Get("archived") == "true" {
			where = append(where, "i.archived_at IS NOT NULL")
		} else {
			where = append(where, "i.archived_at IS NULL")
		}

		// A snooze expires by simply falling into the past; nothing sweeps it.
		if q.Get("snoozed") == "true" {
			where = append(where, "i.snoozed_until > "+args.add(time.Now().Unix()))
		} else {
			where = append(where, "(i.snoozed_until IS NULL OR i.snoozed_until <= "+args.add(time.Now().Unix())+")")
		}

		if severity := q.Get("severity"); severity != "" {
			where = append(where, "i.severity = "+args.add(severity))
		}
		if assignee := q.Get("assigned_to"); assignee != "" {
			if n, err := strconv.ParseInt(assignee, 10, 64); err == nil {
				where = append(where, "i.assigned_to = "+args.add(n))
			}
		}
		if from := q.Get("from"); from != "" {
			if t, err := time.Parse("2006-01-02", from); err == nil {
				where = append(where, "i.triggered_at >= "+args.add(t.UTC().Unix()))
			}
		}
		if to := q.Get("to"); to != "" {
			if t, err := time.Parse("2006-01-02", to); err == nil {
				where = append(where, "i.triggered_at < "+args.add(t.UTC().AddDate(0, 0, 1).Unix()))
			}
		}

		limit := 50
		if l := q.Get("limit"); l != "" {
			if n, err := strconv.Atoi(l); err == nil && n > 0 && n <= 500 {
				limit = n
			}
		}

		order := "i.triggered_at DESC"
		if q.Get("sort") == "severity" {
			order = severityRankSQL("i.severity") + " DESC, i.triggered_at DESC"
		}

		rows, err := db.QueryContext(r.Context(),
			fmt.Sprintf("%s WHERE %s ORDER BY %s LIMIT %s",
				incidentSelectFrom, strings.Join(where, " AND "), order, args.add(limit)),
			args.all()...)
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		defer rows.Close()

		incidents := []models.Incident{}
		for rows.Next() {
			i, err := scanIncident(rows)
			if err != nil {
				respond(w, http.StatusInternalServerError, errResp("internal error"))
				return
			}
			incidents = append(incidents, i)
		}
		respond(w, http.StatusOK, incidents)
	}
}

func handleGetIncident(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id, ok := incidentIDParam(w, r)
		if !ok {
			return
		}
		inc, err := fetchIncident(r.Context(), db, id)
		if err == sql.ErrNoRows {
			respond(w, http.StatusNotFound, errResp("incident not found"))
			return
		}
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		if inc.Alerts, err = incidentAlerts(r, db, id); err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		respond(w, http.StatusOK, inc)
	}
}

func handleIncidentAlerts(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id, ok := incidentIDParam(w, r)
		if !ok {
			return
		}
		if !incidentExists(w, r, db, id) {
			return
		}
		alerts, err := incidentAlerts(r, db, id)
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		respond(w, http.StatusOK, alerts)
	}
}

func handleIncidentTimeline(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id, ok := incidentIDParam(w, r)
		if !ok {
			return
		}
		if !incidentExists(w, r, db, id) {
			return
		}

		rows, err := db.QueryContext(r.Context(), `
			SELECT e.id, e.incident_id, e.type, e.user_id, u.username,
			       e.alert_id, e.detail, e.created_at
			FROM   incident_events e
			LEFT   JOIN users u ON u.id = e.user_id
			WHERE  e.incident_id = $1
			ORDER  BY e.created_at ASC, e.id ASC`, id)
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		defer rows.Close()

		events := []models.IncidentEvent{}
		for rows.Next() {
			var e models.IncidentEvent
			var ts int64
			if err := rows.Scan(&e.ID, &e.IncidentID, &e.Type, &e.UserID, &e.Username,
				&e.AlertID, &e.Detail, &ts); err != nil {
				respond(w, http.StatusInternalServerError, errResp("internal error"))
				return
			}
			e.CreatedAt = time.Unix(ts, 0).UTC()
			events = append(events, e)
		}
		respond(w, http.StatusOK, events)
	}
}

func handleIncidentAcknowledge(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id, ok := incidentIDParam(w, r)
		if !ok {
			return
		}
		user, _ := userFromContext(r.Context())
		acked, err := acknowledgeIncident(r.Context(), db, id, user.ID)
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		if !acked {
			if !incidentExists(w, r, db, id) {
				return
			}
			respond(w, http.StatusConflict, errResp("incident is resolved"))
			return
		}
		respondIncident(w, r, db, id)
	}
}

func handleIncidentUnacknowledge(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id, ok := incidentIDParam(w, r)
		if !ok {
			return
		}
		user, _ := userFromContext(r.Context())
		if !updateOpenIncident(w, r, db, id,
			`UPDATE incidents SET status = 'triggered', acknowledged_by = NULL, acknowledged_at = NULL
			  WHERE id = $1 AND resolved_at IS NULL`, id) {
			return
		}
		if err := logEvent(r.Context(), db, id, evUnacknowledged, &user.ID, nil, nil); err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		w.WriteHeader(http.StatusNoContent)
	}
}

// handleIncidentResolve closes an incident by hand. This is terminal: a later
// occurrence opens a new incident rather than reopening this one, which is what
// stops a resolved incident from reappearing on the next repeat_interval
// re-send of an alert that never stopped firing. Use snooze for "not now".
func handleIncidentResolve(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id, ok := incidentIDParam(w, r)
		if !ok {
			return
		}
		user, _ := userFromContext(r.Context())
		if !updateOpenIncident(w, r, db, id,
			`UPDATE incidents SET status = 'resolved', resolved_at = $1, resolution_source = $2
			  WHERE id = $3 AND resolved_at IS NULL`,
			time.Now().Unix(), incidentResolutionManual, id) {
			return
		}
		if err := logEvent(r.Context(), db, id, evResolved, &user.ID, nil, nil); err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		respondIncident(w, r, db, id)
	}
}

func handleIncidentAssign(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id, ok := incidentIDParam(w, r)
		if !ok {
			return
		}
		var req struct {
			UserID int64 `json:"user_id"`
		}
		if err := decodeJSON(r, &req); err != nil {
			respond(w, http.StatusBadRequest, errResp("invalid request body"))
			return
		}
		if req.UserID == 0 {
			respond(w, http.StatusBadRequest, errResp("user_id is required"))
			return
		}
		var exists int
		if err := db.QueryRowContext(r.Context(),
			"SELECT 1 FROM users WHERE id = $1", req.UserID).Scan(&exists); err != nil {
			respond(w, http.StatusNotFound, errResp("user not found"))
			return
		}

		if !updateOpenIncident(w, r, db, id,
			"UPDATE incidents SET assigned_to = $1 WHERE id = $2 AND resolved_at IS NULL",
			req.UserID, id) {
			return
		}
		// On an "assigned" event user_id is the assignee, not the actor.
		if err := logEvent(r.Context(), db, id, evAssigned, &req.UserID, nil, nil); err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		respondIncident(w, r, db, id)
	}
}

// handleIncidentSnooze hides an incident from the default queue without closing
// it. Accepts either an absolute {"until": RFC3339} or a relative
// {"duration": "2h"}.
func handleIncidentSnooze(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id, ok := incidentIDParam(w, r)
		if !ok {
			return
		}
		var req struct {
			Until    string `json:"until"`
			Duration string `json:"duration"`
		}
		if err := decodeJSON(r, &req); err != nil {
			respond(w, http.StatusBadRequest, errResp("invalid request body"))
			return
		}

		var until time.Time
		switch {
		case req.Until != "":
			t, err := time.Parse(time.RFC3339, req.Until)
			if err != nil {
				respond(w, http.StatusBadRequest, errResp("invalid until (expected RFC3339)"))
				return
			}
			until = t
		case req.Duration != "":
			d, err := time.ParseDuration(req.Duration)
			if err != nil {
				respond(w, http.StatusBadRequest, errResp("invalid duration"))
				return
			}
			until = time.Now().Add(d)
		default:
			respond(w, http.StatusBadRequest, errResp("until or duration is required"))
			return
		}
		if !until.After(time.Now()) {
			respond(w, http.StatusBadRequest, errResp("snooze must end in the future"))
			return
		}

		user, _ := userFromContext(r.Context())
		if !updateOpenIncident(w, r, db, id,
			"UPDATE incidents SET snoozed_until = $1 WHERE id = $2 AND resolved_at IS NULL",
			until.Unix(), id) {
			return
		}
		detail := until.UTC().Format(time.RFC3339)
		if err := logEvent(r.Context(), db, id, evSnoozed, &user.ID, nil, &detail); err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		respondIncident(w, r, db, id)
	}
}

func handleIncidentUnsnooze(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id, ok := incidentIDParam(w, r)
		if !ok {
			return
		}
		user, _ := userFromContext(r.Context())
		if !updateOpenIncident(w, r, db, id,
			"UPDATE incidents SET snoozed_until = NULL WHERE id = $1 AND resolved_at IS NULL", id) {
			return
		}
		if err := logEvent(r.Context(), db, id, evUnsnoozed, &user.ID, nil, nil); err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		w.WriteHeader(http.StatusNoContent)
	}
}

func handleIncidentArchive(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id, ok := incidentIDParam(w, r)
		if !ok {
			return
		}
		res, err := db.ExecContext(r.Context(),
			"UPDATE incidents SET archived_at = "+nowEpoch+" WHERE id = $1", id)
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		if n, _ := res.RowsAffected(); n == 0 {
			respond(w, http.StatusNotFound, errResp("incident not found"))
			return
		}
		respondIncident(w, r, db, id)
	}
}

func handleIncidentUnarchive(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id, ok := incidentIDParam(w, r)
		if !ok {
			return
		}
		res, err := db.ExecContext(r.Context(),
			"UPDATE incidents SET archived_at = NULL WHERE id = $1", id)
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		if n, _ := res.RowsAffected(); n == 0 {
			respond(w, http.StatusNotFound, errResp("incident not found"))
			return
		}
		w.WriteHeader(http.StatusNoContent)
	}
}

// handleCreateNote adds a note to the timeline. Notes are ordinary events, so a
// single query renders the whole story of an incident in order.
func handleCreateNote(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id, ok := incidentIDParam(w, r)
		if !ok {
			return
		}
		var req struct {
			Content string `json:"content"`
		}
		if err := decodeJSON(r, &req); err != nil {
			respond(w, http.StatusBadRequest, errResp("invalid request body"))
			return
		}
		if req.Content == "" {
			respond(w, http.StatusBadRequest, errResp("content is required"))
			return
		}
		if !incidentExists(w, r, db, id) {
			return
		}

		user, _ := userFromContext(r.Context())
		now := time.Now()
		var eventID int64
		err := db.QueryRowContext(r.Context(), `
			INSERT INTO incident_events (incident_id, type, user_id, detail, created_at)
			VALUES ($1, $2, $3, $4, $5)
			RETURNING id`, id, evNote, user.ID, req.Content, now.Unix()).Scan(&eventID)
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}

		respond(w, http.StatusCreated, models.IncidentEvent{
			ID:         eventID,
			IncidentID: id,
			Type:       evNote,
			UserID:     &user.ID,
			Username:   &user.Username,
			Detail:     &req.Content,
			CreatedAt:  now.UTC().Truncate(time.Second),
		})
	}
}

// handleDeleteNote removes one of your own notes. Only notes are deletable — the
// rest of the timeline is what actually happened, and is not editable.
func handleDeleteNote(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id, ok := incidentIDParam(w, r)
		if !ok {
			return
		}
		eventID, err := strconv.ParseInt(chi.URLParam(r, "eventID"), 10, 64)
		if err != nil {
			respond(w, http.StatusBadRequest, errResp("invalid note id"))
			return
		}

		user, _ := userFromContext(r.Context())
		res, err := db.ExecContext(r.Context(), `
			DELETE FROM incident_events
			 WHERE id = $1 AND incident_id = $2 AND type = $3 AND user_id = $4`,
			eventID, id, evNote, user.ID)
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		if n, _ := res.RowsAffected(); n == 0 {
			respond(w, http.StatusNotFound, errResp("note not found"))
			return
		}
		w.WriteHeader(http.StatusNoContent)
	}
}

// ---------------------------------------------------------------------------
// Shared handler plumbing
// ---------------------------------------------------------------------------

func incidentIDParam(w http.ResponseWriter, r *http.Request) (int64, bool) {
	id, err := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64)
	if err != nil {
		respond(w, http.StatusBadRequest, errResp("invalid incident id"))
		return 0, false
	}
	return id, true
}

func incidentExists(w http.ResponseWriter, r *http.Request, db *sql.DB, id int64) bool {
	var exists int
	if err := db.QueryRowContext(r.Context(),
		"SELECT 1 FROM incidents WHERE id = $1", id).Scan(&exists); err != nil {
		respond(w, http.StatusNotFound, errResp("incident not found"))
		return false
	}
	return true
}

// updateOpenIncident runs a mutation that is only valid while an incident is
// open. The query must be constrained to `resolved_at IS NULL`, so no rows means
// either the incident does not exist or it is already closed — two different
// answers the caller should not have to distinguish itself.
func updateOpenIncident(w http.ResponseWriter, r *http.Request, db *sql.DB, id int64, query string, args ...any) bool {
	res, err := db.ExecContext(r.Context(), query, args...)
	if err != nil {
		respond(w, http.StatusInternalServerError, errResp("internal error"))
		return false
	}
	if n, _ := res.RowsAffected(); n > 0 {
		return true
	}
	if !incidentExists(w, r, db, id) {
		return false
	}
	respond(w, http.StatusConflict, errResp("incident is resolved"))
	return false
}

func respondIncident(w http.ResponseWriter, r *http.Request, db *sql.DB, id int64) {
	inc, err := fetchIncident(r.Context(), db, id)
	if err != nil {
		respond(w, http.StatusInternalServerError, errResp("internal error"))
		return
	}
	respond(w, http.StatusOK, inc)
}

// incidentAlerts loads the alerts under an incident, newest signal first.
func incidentAlerts(r *http.Request, db *sql.DB, id int64) ([]models.Alert, error) {
	rows, err := db.QueryContext(r.Context(), alertSelectFrom+`
		JOIN incident_alerts m ON m.alert_id = a.id
		WHERE m.incident_id = $1
		ORDER BY a.received_at DESC`, id)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	alerts := []models.Alert{}
	for rows.Next() {
		a, err := scanAlert(rows)
		if err != nil {
			return nil, err
		}
		alerts = append(alerts, a)
	}
	return alerts, rows.Err()
}