with_unique_warnings <- function(expr) {
  # utility function that prevents the same warning being cast more than once
  seen <- character(0)
  withCallingHandlers(expr, warning = function(w) {
    msg <- conditionMessage(w)
    if (msg %in% seen) {
      invokeRestart("muffleWarning")
    } else {
      seen <<- c(seen, msg)
    }
  })
}

# small sample corrections to variance estimates
small_sample_correction <- function(ic, type, var.adj) {
  V <- var_ic(ic)
  ## Small-sample corrections for clustered data
  K <- NROW(ic)
  N <- attributes(ic)$N
  if (is.null(N)) N <- K
  p <- NCOL(ic)
  adj0 <- K/(K-p) ## Mancl & DeRouen, 2001
  adj1 <- K/(K-1) ## Mancl & DeRouen, 2001
  adj2 <- (N-1)/(N-p)*(K/(K-1)) ## Morel,Bokossa & Neerchal, 2003
  if (tolower(type[1])=="mbn" && !is.null(attributes(ic)$bread)) {
    V0 <- V
    iI0 <- attributes(ic)$bread
    I0 <- Inverse(iI0)
    delta <- min(0.5, p / (K - p))
    phi <- max(1, tr(I0%*%V0)*adj2/p)
    V <- adj2*V0 + delta*phi*iI0
  }
  if (tolower(type[1])=="df") {
    V <- adj0*V
  }
  if (tolower(type[1])=="df1") {
    V <- adj1*V
  }
  if (tolower(type[1])=="df2") {
    V <- adj2*V
  }
  if (tolower(type[1])%in%c("hc3", "hc4")) {
    ic <- cbind(ic)
    S <- Inverse(crossprod(ic), tol=sqrt(.Machine$double.eps))
    h_emp <- rowSums((ic %*% S) * ic) # empirical h, lev.
    n <- nrow(ic)
    ## h_emp <- pmin(h_emp, 0.99) * (n-1)/n  # Truncate leverage to prevent division by zero
    if (tolower(type[1])=="hc3") {
      ## phi_norm <- sqrt(rowSums(ic^2))
      ## ex_kurt <- (mean((phi_norm - mean(phi_norm))^4) / var(phi_norm)^2) - 3
      ## alpha <- exp(-max(0, ex_kurt) / 25)
      v.alpha <- ifelse(missing(var.adj), 0.25, var.adj)
      h <- v.alpha * h_emp + (1 - v.alpha) * (ncol(ic) / n)
      adj <- 1 / (1 - h)
    } else {
      ## Cribari-Neto (2004)
      delta <- pmin(1.5, n/ncol(ic) * h_emp)
      adj <- 1 / (1 - h_emp)**delta
    }
    for (i in seq_len(NCOL(ic))) ic[, i] <- ic[, i] * adj
    V <- var_ic(ic)
  }
  return(V)
}

# construct coefficient matrix with confidence limits and two-sided p-values
estimate_coefmat <- function(est, se, df, level = 0.95, null = 0) {
  alpha <- 1 - level
  alpha.str <- paste(c(alpha/2, 1 -alpha/2)*100, "", sep="%")
  if (!is.null(df)) {
    za <- qt(1-alpha/2, df=df)
    pval <- 2*pt(abs((est-null) / se), df=df, lower.tail=FALSE)
  } else {
    za <- qnorm(1-alpha/2)
    pval <- 2*pnorm(abs((est-null)/ se), lower.tail=FALSE)
  }
  res <- cbind(est, se, est - za * se, est + za * se, pval)
  colnames(res) <- c("Estimate", "Std.Err", alpha.str, "P-value")
  return(res)
}

#' Summary of estimate objects
#'
#' Computes hypothesis tests, contrasts, and small-sample corrections for
#' an [estimate] object. The arguments `null`, `contrast`, `type`, and
#' `var.adj` were previously available on [estimate.default()] and have
#' been moved here.
#'
#' @param object an `estimate` object.
#' @param contrast (optional) contrast matrix for the final Wald test.
#' @param null (optional) null hypothesis to test.
#' @param type type of small-sample correction. Requires the estimate to have
#'   been computed with `IC=TRUE` (the default).
#' @param var.adj variance adjustment parameter for small-sample correction.
#'   Requires the estimate to have been computed with `IC=TRUE` (the default).
#' @param df degrees of freedom for t-based inference (default: `NULL` for
#'   Gaussian approximation; when set, confidence intervals and p-values use the
#'   t-distribution with `df` degrees of freedom)
#' @param level level of confidence limits (default 0.95)
#' @param transform (optional) function applied to the point estimates and
#'   confidence interval bounds *after* inference is performed on the original
#'   scale. Useful for variance-stabilizing transformations, e.g., compute CIs
#'   on the `atanh` (Fisher z) scale and back-transform with `tanh`.
#' @param print (optional) custom print function for the resulting
#'   `summary.estimate` object
#' @param ... additional arguments passed to [contr].
#' @seealso [estimate.default()]
#' @export
summary.estimate <- function(object,
                             contrast,
                             ...,
                             null = 0,
                             level = 0.95,
                             type,
                             var.adj = 0.25,
                             df,
                             transform = NULL,
                             print = NULL) {
  with_unique_warnings({
    p <- coef(object)
    if (missing(df)) df <- object$df
    if (missing(contrast)) contrast <- diag(1, nrow=length(p))
    correction <- !missing(type)
    if (correction) {
      if (is.null(object$IC)) {
        stop(
          "Small-sample corrections in summary() require an estimate ",
          "computed with IC=TRUE."
        )
      }
      V <- small_sample_correction(IC(object), type=type, var.adj=var.adj)
    } else {
      V <- vcov(object)
    }
    ## Preserve dimnames on vcov: the recall path through type/var.adj
    ## corrections builds V from the influence function and may drop
    ## dimnames. Restore them from the original coef names so the
    ## summary output is consistent with the deprecated estimate() path.
    if (!is.null(V) && is.null(dimnames(V)) &&
        !is.null(names(p)) &&
        nrow(V) == length(p)) {
      dimnames(V) <- list(names(p), names(p))
    }

    if (is.vector(contrast) || is.list(contrast)) {
      contrast <- contr(contrast, names(object$coef), ...)
    }

    cc0 <- estimate_coefmat(p, diag(V)**.5, df=df, level=level, null=null)
    rownames(cc0) <- rownames(parameter(object))
    waldtest <- compare(object, contrast=contrast, null=null, vcov=V)
    class(object) <- "list"
    res <- c(object[c("coef", "coefmat", "vcov", "call",
                      "ncluster", "model.index")], list(compare=waldtest))
    res$coefmat <- cc0
    if (!is.null(transform)) {
      res$coefmat[, c(1, 3, 4)] <- do.call(transform,
                                           list(res$coefmat[, c(1, 3, 4)]))
      res$coefmat[, 2] <- NA
      res$vcov <- NULL
      res$coef <- res$coefmat[, 1, drop=TRUE]
    }
    res$print <- print
    class(res) <- c("summary.estimate", "estimate")
    return(res)
  })
}

#' @export
print.summary.estimate <- function(x, ...) {
  if (!is.null(x$print)) {
    x$print(x, ...)
    return(invisible(x))
  }
  print.estimate(x, type=2L, ...)
  if (!is.null(attributes(x)$extra)) {
    print(attributes(x)$extra)
  }
  return(invisible(x))
}

#' @export
coef.summary.estimate <- function(object, ...) {
  return(object$coef)
}

#' @export
confint.summary.estimate <- function(object, ...) {
  parameter(object)[, 3:4, drop=FALSE]
}

#' @export
parameter.summary.estimate <- function(x, ...) {
  return(x$coefmat)
}

#' @export
vcov.summary.estimate <- function(object, ...) {
  res <- object$vcov
  p <- coef(object)
  if (is.null(res)) {
    res <- matrix(NA, length(p), length(p))
    dimnames(res) <- list(names(p), names(p))
  }
  return(res)
}

#' Concatenate summary.estimate objects
#'
#' When all arguments are `summary.estimate` objects, they are merged into a
#' single `summary.estimate` object. When some arguments are not
#' `summary.estimate` objects but are named numeric scalars/vectors, an object
#' of class `summary.estimate` is returned with an additional `extra` attribute
#' that contains the provided numeric scalars/vectors. This is useful for
#' bundling auxiliary per-iteration information (e.g., convergence status)
#' alongside an estimate for use with [sim.default()].
#'
#' @param ... `summary.estimate` objects and/or named numeric values
#' @examples
#' e1 <- estimate(coef = 1, IC = scale(rnorm(10)), id = 1:10, labels = "a1")
#' e2 <- estimate(coef = 2, IC = scale(rnorm(10)), id = 1:10, labels = "a2")
#'
#' # concatenating two summary.estimate objects
#' c(e1, e2)
#'
#' # concatenating one summary.estimate object with one numerical variable
#' ss <- c(summary(e1), niter = 2)
#' print(ss)
#' attributes(ss)$extra
#' @export
c.summary.estimate <- function(...) {
  args <- list(...)
  if (length(args) == 1) return(args[[1]])

  mask <- sapply(args, function(x) inherits(x, "summary.estimate"))
  summary_objects <- args[mask]

  extras_existing <- unlist(
    lapply(summary_objects, function(x) attributes(x)$extra)
  )

  extras <- c(extras_existing, unlist(args[!mask]))

  .print <- function(x, digits = 4, ...) {
    cat("Concatenated summary.estimate objects: \n")
    print(cli::rule(width = min(cli::console_width(), 60)))
    print(x$coefmat, digits = digits)
    print(cli::rule(width = min(cli::console_width(), 60)))
    if (!is.null(attributes(x)$extra)) {
      print(attributes(x)$extra)
    }
  }

  res <- structure(list(
    coefmat = Reduce(rbind, lapply(summary_objects, function(x) parameter(x))),
    coef = as.vector(
      Reduce(rbind, lapply(summary_objects, function(x) coef(x)))
    ),
    vcov = cbind(Reduce(function(...) blockdiag(..., pad=NA),
                        lapply(summary_objects, function(x) vcov(x)))),
    objects = summary_objects,
    print = .print # consumed by print.summary.estimate
  ), class = c("summary.estimate", "estimate")
  )
  names(res$coef) <- rownames(res$coefmat)
  if (length(extras) > 0) attr(res, "extra") <- extras

  return(res)
}
