### Copyright (C) 2001-2005  Deepayan Sarkar <Deepayan.Sarkar@R-project.org>
###
### This file is part of the lattice library for R.
### It is made available under the terms of the GNU General Public
### License, version 2, or at your option, any later version,
### incorporated herein by reference.
###
### This program is distributed in the hope that it will be
### useful, but WITHOUT ANY WARRANTY; without even the implied
### warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
### PURPOSE.  See the GNU General Public License for more
### details.
###
### You should have received a copy of the GNU General Public
### License along with this program; if not, write to the Free
### Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
### MA 02111-1307, USA




panel.qqmathline <-
    function(y, distribution, p = c(0.25, 0.75), ...)
{
    y <- as.numeric(y)
    stopifnot(length(p) == 2)

    if (length(y) > 0) {
        yy <- quantile(y, p)
        xx <- distribution(p)
        r <- diff(yy)/diff(xx)
        panel.abline(c( yy[1]-xx[1]*r , r), ...)
    }
}


prepanel.qqmathline <-
    function(y, distribution, f.value = ppoints, p = c(0.25, 0.75), ...)
{
    ##if (!is.numeric(y)) 
    y <- as.numeric(y)
    stopifnot(length(p) == 2)
    n <- length(y)

    if (n > 0)
    {
        yy <- quantile(y, p)
        xx <- distribution(p)
        list(xlim = range(distribution(f.value(n))),
             ylim = range(y),
             dx = diff(xx),
             dy = diff(yy))
    }
    else
    {
        list(xlim = c(NA, NA), ylim = c(NA, NA), dx = 1, dy = 1)
    }
}


prepanel.default.qqmath <-
    function(...)
    prepanel.default.xyplot(...)


panel.qqmath <-
    function(...) panel.xyplot(...)


qqmath <-
    function(formula,
             data = parent.frame(),
             allow.multiple = FALSE,
             outer = TRUE,
             auto.key = FALSE,
             aspect = "fill",
             panel = "panel.qqmath",
             prepanel = NULL,
             scales = list(),
             strip = TRUE,
             groups = NULL,
             xlab,
             xlim,
             ylab,
             ylim,
###          f.value = ppoints,
             f.value = NULL,
             distribution = qnorm,
             drop.unused.levels = lattice.getOption("drop.unused.levels"),
             ...,
             default.scales = list(),
             subscripts = !is.null(groups),
             subset = TRUE)
{

    ## dots <- eval(substitute(list(...)), data, parent.frame())
    dots <- list(...)

    groups <- eval(substitute(groups), data, parent.frame())
    subset <- eval(substitute(subset), data, parent.frame())

    ## Step 1: Evaluate x, y, etc. and do some preprocessing

    form <-
        latticeParseFormula(formula, data, subset = subset,
                            groups = groups, multiple = allow.multiple,
                            outer = outer, subscripts = TRUE,
                            drop = drop.unused.levels)

    groups <- form$groups

    if (!is.function(panel)) panel <- eval(panel)
    if (!is.function(strip)) strip <- eval(strip)
    
    if ("subscripts" %in% names(formals(panel))) subscripts <- TRUE
    if (subscripts) subscr <- form$subscr

    prepanel <-
        if (is.function(prepanel)) prepanel
        else if (is.character(prepanel)) get(prepanel)
        else eval(prepanel)

    distribution.name <- deparse(substitute(distribution))
    distribution <-
        if (is.function(distribution)) distribution 
        else if (is.character(distribution)) get(distribution)
        else eval(distribution)

    cond <- form$condition
    number.of.cond <- length(cond)
    x <- form$right

    if (number.of.cond == 0) {
        strip <- FALSE
        cond <- list(as.factor(rep(1, length(x))))
        number.of.cond <- 1
    }



    



    if(missing(ylab)) ylab <- form$right.name
    if(missing(xlab)) xlab <- distribution.name
    if (is.shingle(x)) stop("x cannot be a shingle")
    ##x <- as.numeric(x)

    ## create a skeleton trellis object with the
    ## less complicated components:

    foo <- do.call("trellis.skeleton",
                   c(list(cond = cond,
                          aspect = aspect,
                          strip = strip,
                          panel = panel,
                          xlab = xlab,
                          ylab = ylab,
                          xlab.default = distribution.name,
                          ylab.default = form$right.name,
                          distribution = distribution),
                     dots))

    dots <- foo$dots # arguments not processed by trellis.skeleton
    foo <- foo$foo
    foo$call <- match.call()

    ## Step 2: Compute scales.common (leaving out limits for now)

    ## scales <- eval(substitute(scales), data, parent.frame())
    if (is.character(scales)) scales <- list(relation = scales)
    scales <- updateList(default.scales, scales)
    foo <- c(foo, 
             do.call("construct.scales", scales))


    ## Step 3: Decide if limits were specified in call:

    have.xlim <- !missing(xlim)
    if (!is.null(foo$x.scales$limit)) {
        have.xlim <- TRUE
        xlim <- foo$x.scales$limit
    }
    have.ylim <- !missing(ylim)
    if (!is.null(foo$y.scales$limit)) {
        have.ylim <- TRUE
        ylim <- foo$y.scales$limit
    }

    ## Step 4: Decide if log scales are being used:

    have.xlog <- !is.logical(foo$x.scales$log) || foo$x.scales$log
    have.ylog <- !is.logical(foo$y.scales$log) || foo$y.scales$log
    if (have.xlog)
    {
        xlog <- foo$x.scales$log
        xbase <-
            if (is.logical(xlog)) 10
            else if (is.numeric(xlog)) xlog
            else if (xlog == "e") exp(1)

        x <- log(x, xbase)
        if (have.xlim) xlim <- log(xlim, xbase)
    }
    if (have.ylog) {
        warning("cannot use log scale for y, use different distribution")
        foo$y.scales$log <- FALSE
    }
    
    ## Step 5: Process cond

    cond.max.level <- unlist(lapply(cond, nlevels))


    id.na <- is.na(x)
    for (var in cond)
        id.na <- id.na | is.na(var)
    if (!any(!id.na)) stop("nothing to draw")
    ## Nothing simpler ?


    ## Step 6: Evaluate layout, panel.args.common and panel.args

    foo$panel.args.common <- dots
    if (subscripts) foo$panel.args.common$groups <- groups

    nplots <- prod(cond.max.level)
    if (nplots != prod(sapply(foo$condlevels, length))) stop("mismatch")
    foo$panel.args <- vector(mode = "list", length = nplots)


    cond.current.level <- rep(1, number.of.cond)


    for (panel.number in seq(length = nplots))
    {

        id <- !id.na
        for(i in 1:number.of.cond)
        {
            var <- cond[[i]]
            id <- id &
            if (is.shingle(var))
                ((var >=
                  levels(var)[[cond.current.level[i]]][1])
                 & (var <=
                    levels(var)[[cond.current.level[i]]][2]))
            else (as.numeric(var) == cond.current.level[i])
        }
        if (any(id))
        {
            foo$panel.args[[panel.number]] <-
                if (is.null(f.value)) # exact data instead of quantiles
                    list(x = distribution(ppoints(length(x[id]))), 
                         y = sort(x[id]))
                else
                    list(x = distribution(f.value(length(x[id]))), 
                         y = quantile(x[id], f.value(length(x[id]))))
        }
        else
            foo$panel.args[[panel.number]] <-
                list(x = numeric(0), y = numeric(0))

        if (subscripts)
            foo$panel.args[[panel.number]]$subscripts <-
                subscr[id]

        cond.current.level <-
            cupdate(cond.current.level,
                    cond.max.level)
    }


    more.comp <- c(limits.and.aspect(prepanel.default.qqmath,
                                     prepanel = prepanel, 
                                     have.xlim = have.xlim, xlim = xlim, 
                                     have.ylim = have.ylim, ylim = ylim, 
                                     x.relation = foo$x.scales$relation,
                                     y.relation = foo$y.scales$relation,
                                     panel.args.common = foo$panel.args.common,
                                     panel.args = foo$panel.args,
                                     aspect = aspect,
                                     nplots = nplots,
                                     x.axs = foo$x.scales$axs,
                                     y.axs = foo$y.scales$axs),
                   cond.orders(foo))
    foo[names(more.comp)] <- more.comp

    if (is.null(foo$legend) && !is.null(groups) &&
        (is.list(auto.key) || (is.logical(auto.key) && auto.key)))
    {
        foo$legend <-
            list(list(fun = "drawSimpleKey",
                      args =
                      updateList(list(text = levels(as.factor(groups)),
                                      points = TRUE,
                                      rectangles = FALSE,
                                      lines = FALSE), 
                                 if (is.list(auto.key)) auto.key else list())))
        foo$legend[[1]]$x <- foo$legend[[1]]$args$x
        foo$legend[[1]]$y <- foo$legend[[1]]$args$y
        foo$legend[[1]]$corner <- foo$legend[[1]]$args$corner

        names(foo$legend) <- 
            if (any(c("x", "y", "corner") %in% names(foo$legend[[1]]$args)))
                "inside"
            else
                "top"
        if (!is.null(foo$legend[[1]]$args$space))
            names(foo$legend) <- foo$legend[[1]]$args$space
    }

    class(foo) <- "trellis"
    foo
}