// backend/admin.go

package main

import (
	"context"
	"errors"
	"net/http"
	"strings"
	"time"

	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgconn"
	"golang.org/x/crypto/bcrypt"
)

type AdminTeam struct {
	ID        string    `json:"id"`
	Name      string    `json:"name"`
	Initial   string    `json:"initial"`
	Href      string    `json:"href"`
	CreatedAt time.Time `json:"createdAt"`
	UpdatedAt time.Time `json:"updatedAt"`
}

type AdminUser struct {
	ID             string      `json:"id"`
	Username       string      `json:"username"`
	DisplayName    string      `json:"displayName"`
	Email          string      `json:"email"`
	Avatar         string      `json:"avatar"`
	Unit           string      `json:"unit"`
	Group          string      `json:"group"`
	Rights         []string    `json:"rights"`
	Teams          []AdminTeam `json:"teams"`
	Online         bool        `json:"onlineStatus"`
	PresenceStatus string      `json:"presenceStatus"`
	LastSeenAt     *time.Time  `json:"lastSeenAt"`
	CreatedAt      time.Time   `json:"createdAt"`
	UpdatedAt      time.Time   `json:"updatedAt"`
}

type AdminUserRequest struct {
	Username    string   `json:"username"`
	DisplayName string   `json:"displayName"`
	Email       string   `json:"email"`
	Password    string   `json:"password"`
	Avatar      string   `json:"avatar"`
	Unit        string   `json:"unit"`
	Group       string   `json:"group"`
	Rights      []string `json:"rights"`
	TeamIDs     []string `json:"teamIds"`
}

type AdminTeamRequest struct {
	Name    string `json:"name"`
	Initial string `json:"initial"`
	Href    string `json:"href"`
}

func normalizeAdminUserInput(input *AdminUserRequest) {
	input.Username = strings.TrimSpace(input.Username)
	input.DisplayName = strings.TrimSpace(input.DisplayName)
	input.Email = strings.TrimSpace(input.Email)
	input.Password = strings.TrimSpace(input.Password)
	input.Avatar = strings.TrimSpace(input.Avatar)
	input.Unit = strings.TrimSpace(input.Unit)
	input.Group = strings.TrimSpace(input.Group)

	if input.Group == "" {
		input.Group = "user"
	}

	input.Rights = cleanStringList(input.Rights)
	input.TeamIDs = cleanStringList(input.TeamIDs)
}

func ensureAdminUserLookupValues(ctx context.Context, tx pgx.Tx, unit string) error {
	return ensureOptionalDeviceLookupValue(ctx, tx, "user_units", unit)
}

func normalizeAdminTeamInput(input *AdminTeamRequest) {
	input.Name = strings.TrimSpace(input.Name)
	input.Initial = strings.TrimSpace(input.Initial)
	input.Href = strings.TrimSpace(input.Href)

	if input.Initial == "" && input.Name != "" {
		input.Initial = strings.ToUpper(string([]rune(input.Name)[0]))
	}

	if input.Href == "" {
		input.Href = "#"
	}
}

func cleanStringList(values []string) []string {
	result := []string{}
	seen := map[string]bool{}

	for _, value := range values {
		value = strings.TrimSpace(value)
		if value == "" || seen[value] {
			continue
		}

		seen[value] = true
		result = append(result, value)
	}

	return result
}

func (s *Server) handleAdminListUsers(w http.ResponseWriter, r *http.Request) {
	rows, err := s.db.Query(
		r.Context(),
		`
		SELECT
			id::TEXT,
			COALESCE(username, ''),
			COALESCE(display_name, ''),
			email,
			COALESCE(avatar, ''),
			COALESCE(unit, ''),
			COALESCE(user_group, ''),
			rights,
			`+presenceStatusSQL+`,
			last_seen_at,
			created_at,
			updated_at
		FROM users
		ORDER BY display_name ASC, email ASC
		`,
	)

	if err != nil {
		writeError(w, http.StatusInternalServerError, "Benutzer konnten nicht geladen werden")
		return
	}
	defer rows.Close()

	users := []AdminUser{}
	userIndexByID := map[string]int{}

	for rows.Next() {
		var user AdminUser

		if err := rows.Scan(
			&user.ID,
			&user.Username,
			&user.DisplayName,
			&user.Email,
			&user.Avatar,
			&user.Unit,
			&user.Group,
			&user.Rights,
			&user.PresenceStatus,
			&user.LastSeenAt,
			&user.CreatedAt,
			&user.UpdatedAt,
		); err != nil {
			writeError(w, http.StatusInternalServerError, "Benutzer konnten nicht gelesen werden")
			return
		}

		user.Teams = []AdminTeam{}
		user.Online = user.PresenceStatus == "online"

		users = append(users, user)
		userIndexByID[user.ID] = len(users) - 1
	}

	if err := rows.Err(); err != nil {
		writeError(w, http.StatusInternalServerError, "Benutzer konnten nicht vollständig gelesen werden")
		return
	}

	teamRows, err := s.db.Query(
		r.Context(),
		`
		SELECT
			ut.user_id::TEXT,
			t.id::TEXT,
			t.name,
			t.initial,
			t.href,
			t.created_at,
			t.updated_at
		FROM user_teams ut
		JOIN teams t ON t.id = ut.team_id
		ORDER BY t.name ASC
		`,
	)

	if err != nil {
		writeError(w, http.StatusInternalServerError, "Team-Zuordnungen konnten nicht geladen werden")
		return
	}
	defer teamRows.Close()

	for teamRows.Next() {
		var userID string
		var team AdminTeam

		if err := teamRows.Scan(
			&userID,
			&team.ID,
			&team.Name,
			&team.Initial,
			&team.Href,
			&team.CreatedAt,
			&team.UpdatedAt,
		); err != nil {
			writeError(w, http.StatusInternalServerError, "Team-Zuordnungen konnten nicht gelesen werden")
			return
		}

		userIndex, ok := userIndexByID[userID]
		if !ok {
			continue
		}

		users[userIndex].Teams = append(users[userIndex].Teams, team)
	}

	if err := teamRows.Err(); err != nil {
		writeError(w, http.StatusInternalServerError, "Team-Zuordnungen konnten nicht vollständig gelesen werden")
		return
	}

	writeJSON(w, http.StatusOK, map[string]any{
		"users": users,
	})
}

func (s *Server) handleAdminCreateUser(w http.ResponseWriter, r *http.Request) {
	var input AdminUserRequest

	if err := readJSON(r, &input); err != nil {
		writeError(w, http.StatusBadRequest, "Invalid JSON")
		return
	}

	normalizeAdminUserInput(&input)

	if input.Email == "" {
		writeError(w, http.StatusBadRequest, "E-Mail ist erforderlich")
		return
	}

	if input.Password == "" {
		writeError(w, http.StatusBadRequest, "Passwort ist erforderlich")
		return
	}

	passwordHash, err := bcrypt.GenerateFromPassword([]byte(input.Password), bcrypt.DefaultCost)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "Passwort konnte nicht verarbeitet werden")
		return
	}

	tx, err := s.db.Begin(r.Context())
	if err != nil {
		writeError(w, http.StatusInternalServerError, "Benutzer konnte nicht erstellt werden")
		return
	}
	defer tx.Rollback(r.Context())

	if err := ensureAdminUserLookupValues(r.Context(), tx, input.Unit); err != nil {
		writeError(w, http.StatusInternalServerError, "Einheit konnte nicht gespeichert werden")
		return
	}

	var userID string

	err = tx.QueryRow(
		r.Context(),
		`
		INSERT INTO users (
			username,
			display_name,
			email,
			password_hash,
			avatar,
			unit,
			user_group,
			rights
		)
		VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
		RETURNING id::TEXT
		`,
		input.Username,
		input.DisplayName,
		input.Email,
		string(passwordHash),
		input.Avatar,
		input.Unit,
		input.Group,
		input.Rights,
	).Scan(&userID)

	if err != nil {
		var pgErr *pgconn.PgError

		if errors.As(err, &pgErr) && pgErr.Code == "23505" {
			writeError(w, http.StatusConflict, "Benutzername oder E-Mail existiert bereits")
			return
		}

		writeError(w, http.StatusInternalServerError, "Benutzer konnte nicht erstellt werden")
		return
	}

	if err := replaceUserTeams(r.Context(), tx, userID, input.TeamIDs); err != nil {
		writeError(w, http.StatusInternalServerError, "Teams konnten nicht zugewiesen werden")
		return
	}

	if err := tx.Commit(r.Context()); err != nil {
		writeError(w, http.StatusInternalServerError, "Benutzer konnte nicht erstellt werden")
		return
	}

	if createdUser, err := s.getUserByID(r.Context(), userID); err == nil {
		s.publishUserProfileEvent("user.created", createdUser)
	}

	writeJSON(w, http.StatusCreated, map[string]any{
		"ok": true,
	})
}

func (s *Server) handleAdminUpdateUser(w http.ResponseWriter, r *http.Request) {
	userID := strings.TrimSpace(r.PathValue("id"))

	if userID == "" {
		writeError(w, http.StatusBadRequest, "Benutzer-ID fehlt")
		return
	}

	var input AdminUserRequest

	if err := readJSON(r, &input); err != nil {
		writeError(w, http.StatusBadRequest, "Invalid JSON")
		return
	}

	normalizeAdminUserInput(&input)

	if input.Email == "" {
		writeError(w, http.StatusBadRequest, "E-Mail ist erforderlich")
		return
	}

	tx, err := s.db.Begin(r.Context())
	if err != nil {
		writeError(w, http.StatusInternalServerError, "Benutzer konnte nicht aktualisiert werden")
		return
	}
	defer tx.Rollback(r.Context())

	if err := ensureAdminUserLookupValues(r.Context(), tx, input.Unit); err != nil {
		writeError(w, http.StatusInternalServerError, "Einheit konnte nicht gespeichert werden")
		return
	}

	if input.Password != "" {
		passwordHash, err := bcrypt.GenerateFromPassword([]byte(input.Password), bcrypt.DefaultCost)
		if err != nil {
			writeError(w, http.StatusInternalServerError, "Passwort konnte nicht verarbeitet werden")
			return
		}

		_, err = tx.Exec(
			r.Context(),
			`
			UPDATE users
			SET
				username = $2,
				display_name = $3,
				email = $4,
				password_hash = $5,
				avatar = $6,
				unit = $7,
				user_group = $8,
				rights = $9,
				updated_at = now()
			WHERE id = $1
			`,
			userID,
			input.Username,
			input.DisplayName,
			input.Email,
			string(passwordHash),
			input.Avatar,
			input.Unit,
			input.Group,
			input.Rights,
		)

		if err != nil {
			writeError(w, http.StatusInternalServerError, "Benutzer konnte nicht aktualisiert werden")
			return
		}
	} else {
		_, err = tx.Exec(
			r.Context(),
			`
			UPDATE users
			SET
				username = $2,
				display_name = $3,
				email = $4,
				avatar = $5,
				unit = $6,
				user_group = $7,
				rights = $8,
				updated_at = now()
			WHERE id = $1
			`,
			userID,
			input.Username,
			input.DisplayName,
			input.Email,
			input.Avatar,
			input.Unit,
			input.Group,
			input.Rights,
		)

		if err != nil {
			writeError(w, http.StatusInternalServerError, "Benutzer konnte nicht aktualisiert werden")
			return
		}
	}

	if err := replaceUserTeams(r.Context(), tx, userID, input.TeamIDs); err != nil {
		writeError(w, http.StatusInternalServerError, "Teams konnten nicht zugewiesen werden")
		return
	}

	if err := tx.Commit(r.Context()); err != nil {
		writeError(w, http.StatusInternalServerError, "Benutzer konnte nicht aktualisiert werden")
		return
	}

	if updatedUser, err := s.getUserByID(r.Context(), userID); err == nil {
		s.publishUserProfileEvent("user.updated", updatedUser)
	}

	writeJSON(w, http.StatusOK, map[string]any{
		"ok": true,
	})
}

func replaceUserTeams(ctx context.Context, tx pgx.Tx, userID string, teamIDs []string) error {
	if _, err := tx.Exec(ctx, `DELETE FROM user_teams WHERE user_id = $1`, userID); err != nil {
		return err
	}

	for _, teamID := range teamIDs {
		if _, err := tx.Exec(
			ctx,
			`
			INSERT INTO user_teams (user_id, team_id)
			VALUES ($1, $2)
			ON CONFLICT (user_id, team_id) DO NOTHING
			`,
			userID,
			teamID,
		); err != nil {
			return err
		}
	}

	return nil
}

func (s *Server) handleAdminListTeams(w http.ResponseWriter, r *http.Request) {
	rows, err := s.db.Query(
		r.Context(),
		`
		SELECT id::TEXT, name, initial, href, created_at, updated_at
		FROM teams
		ORDER BY name ASC
		`,
	)

	if err != nil {
		writeError(w, http.StatusInternalServerError, "Teams konnten nicht geladen werden")
		return
	}
	defer rows.Close()

	teams := []AdminTeam{}

	for rows.Next() {
		var team AdminTeam

		if err := rows.Scan(
			&team.ID,
			&team.Name,
			&team.Initial,
			&team.Href,
			&team.CreatedAt,
			&team.UpdatedAt,
		); err != nil {
			writeError(w, http.StatusInternalServerError, "Teams konnten nicht gelesen werden")
			return
		}

		teams = append(teams, team)
	}

	writeJSON(w, http.StatusOK, map[string]any{
		"teams": teams,
	})
}

func (s *Server) handleAdminCreateTeam(w http.ResponseWriter, r *http.Request) {
	var input AdminTeamRequest

	if err := readJSON(r, &input); err != nil {
		writeError(w, http.StatusBadRequest, "Invalid JSON")
		return
	}

	normalizeAdminTeamInput(&input)

	if input.Name == "" {
		writeError(w, http.StatusBadRequest, "Teamname ist erforderlich")
		return
	}

	_, err := s.db.Exec(
		r.Context(),
		`
		INSERT INTO teams (name, initial, href)
		VALUES ($1, $2, $3)
		`,
		input.Name,
		input.Initial,
		input.Href,
	)

	if err != nil {
		writeError(w, http.StatusInternalServerError, "Team konnte nicht erstellt werden")
		return
	}

	writeJSON(w, http.StatusCreated, map[string]any{
		"ok": true,
	})
}

func (s *Server) handleAdminUpdateTeam(w http.ResponseWriter, r *http.Request) {
	teamID := strings.TrimSpace(r.PathValue("id"))

	if teamID == "" {
		writeError(w, http.StatusBadRequest, "Team-ID fehlt")
		return
	}

	var input AdminTeamRequest

	if err := readJSON(r, &input); err != nil {
		writeError(w, http.StatusBadRequest, "Invalid JSON")
		return
	}

	normalizeAdminTeamInput(&input)

	if input.Name == "" {
		writeError(w, http.StatusBadRequest, "Teamname ist erforderlich")
		return
	}

	_, err := s.db.Exec(
		r.Context(),
		`
		UPDATE teams
		SET name = $2,
		    initial = $3,
		    href = $4,
		    updated_at = now()
		WHERE id = $1
		`,
		teamID,
		input.Name,
		input.Initial,
		input.Href,
	)

	if err != nil {
		writeError(w, http.StatusInternalServerError, "Team konnte nicht aktualisiert werden")
		return
	}

	writeJSON(w, http.StatusOK, map[string]any{
		"ok": true,
	})
}