# Author: Ingo Feinerer

PCorpus <-
function(x,
         readerControl = list(reader = x$defaultreader, language = "en"),
         dbControl = list(dbName = "", dbType = "DB1"))
{
    stopifnot(inherits(x, "Source"))

    readerControl <- prepareReader(readerControl, x$defaultreader)

    if (is.function(readerControl$init))
        readerControl$init()

    if (is.function(readerControl$exit))
        on.exit(readerControl$exit())

    if (!filehash::dbCreate(dbControl$dbName, dbControl$dbType))
        stop("error in creating database")
    db <- filehash::dbInit(dbControl$dbName, dbControl$dbType)

    # Allocate memory in advance if length is known
    tdl <- if (x$length > 0) vector("list", as.integer(x$length)) else list()

    counter <- 1
    while (!eoi(x)) {
        x <- stepNext(x)
        elem <- getElem(x)
        id <- if (is.null(x$names) || is.na(x$names))
            as.character(counter)
        else
            x$names[counter]
        doc <- readerControl$reader(elem, readerControl$language, id)
        filehash::dbInsert(db, meta(doc, "id"), doc)
        if (x$length > 0) tdl[[counter]] <- meta(doc, "id")
        else tdl <- c(tdl, meta(doc, "id"))
        counter <- counter + 1
    }
    if (!is.null(x$names) && !is.na(x$names))
        names(tdl) <- x$names

    structure(list(content = tdl,
                   meta = CorpusMeta(),
                   dmeta = data.frame(row.names = seq_along(tdl)),
                   dbcontrol = dbControl),
              class = c("PCorpus", "Corpus"))
}

VCorpus <- Corpus <-
function(x, readerControl = list(reader = x$defaultreader, language = "en"))
{
    stopifnot(inherits(x, "Source"))

    readerControl <- prepareReader(readerControl, x$defaultreader)

    if (is.function(readerControl$init))
        readerControl$init()

    if (is.function(readerControl$exit))
        on.exit(readerControl$exit())

    # Allocate memory in advance if length is known
    tdl <- if (x$length > 0) vector("list", as.integer(x$length)) else list()

    if (x$vectorized)
        tdl <- mapply(function(elem, id)
                          readerControl$reader(elem, readerControl$language, id),
                      pGetElem(x),
                      id = if (is.null(x$names) || is.na(x$names))
                          as.character(seq_len(x$length))
                      else x$names,
                      SIMPLIFY = FALSE)
    else {
        counter <- 1
        while (!eoi(x)) {
            x <- stepNext(x)
            elem <- getElem(x)
            id <- if (is.null(x$names) || is.na(x$names))
                as.character(counter)
            else
                x$names[counter]
            doc <- readerControl$reader(elem, readerControl$language, id)
            if (x$length > 0)
                tdl[[counter]] <- doc
            else
                tdl <- c(tdl, list(doc))
            counter <- counter + 1
        }
    }
    if (!is.null(x$names) && !is.na(x$names))
        names(tdl) <- x$names

    structure(list(content = tdl,
                   meta = CorpusMeta(),
                   dmeta = data.frame(row.names = seq_along(tdl))),
              class = c("VCorpus", "Corpus"))
}

`[.PCorpus` <-
function(x, i)
{
    if (!missing(i)) {
        x$content <- x$content[i]
        x$dmeta <- x$dmeta[i, , drop = FALSE]
    }
    x
}

`[.VCorpus` <-
function(x, i)
{
    if (!missing(i)) {
        x$content <- x$content[i]
        x$dmeta <- x$dmeta[i, , drop = FALSE]
        if (!is.null(x$lazy))
            x$lazy$index <- x$lazy$index[i]
    }
    x
}

.map_name_index <-
function(x, i)
{
    if (is.character(i))
        match(i, if (is.null(names(x))) meta(x, "id", "local") else names(x))
    else
        i
}

`[[.PCorpus` <-
function(x, i)
{
    i <- .map_name_index(x, i)
    db <- filehash::dbInit(x$dbcontrol[["dbName"]], x$dbcontrol[["dbType"]])
    filehash::dbFetch(db, x$content[[i]])
}
`[[.VCorpus` <-
function(x, i)
{
    i <- .map_name_index(x, i)
    if (!is.null(x$lazy))
        .Call(copyCorpus, x, materialize(x, i))
    x$content[[i]]
}

`[[<-.PCorpus` <-
function(x, i, value)
{
    i <- .map_name_index(x, i)
    db <- filehash::dbInit(x$dbcontrol[["dbName"]], x$dbcontrol[["dbType"]])
    db[[x$content[[i]]]] <- value
    x
}
`[[<-.VCorpus` <-
function(x, i, value)
{
    i <- .map_name_index(x, i)
    # Mark new objects as inactive for lazy mapping
    if (!is.null(x$lazy))
        x$lazy$index[i] <- FALSE
    x$content[[i]] <- value
    x
}

outer_union <-
function(x, y, ...)
{
    if (nrow(x) > 0L)
        x[, setdiff(names(y), names(x))] <- NA
    if (nrow(y) > 0L)
        y[, setdiff(names(x), names(y))] <- NA
    res <- rbind(x, y)
    if (ncol(res) == 0L)
        res <- data.frame(row.names = seq_len(nrow(x) + nrow(y)))
    res
}

c.VCorpus <-
function(..., recursive = FALSE)
{
    args <- list(...)
    x <- args[[1L]]

    if (length(args) == 1L)
        return(x)

    if (!all(unlist(lapply(args, inherits, class(x)))))
        stop("not all arguments are of the same corpus type")

    structure(list(content = do.call("c", lapply(args, content)),
                   meta = structure(do.call("c",
                     lapply(args, function(a) meta(a, type = "corpus"))),
                                    class = "CorpusMeta"),
                   dmeta = Reduce(outer_union, lapply(args, meta))),
              class = c("VCorpus", "Corpus"))
}

c.TextDocument <-
function(..., recursive = FALSE)
{
    args <- list(...)
    x <- args[[1L]]

    if (length(args) == 1L)
        return(x)

    if (!all(unlist(lapply(args, inherits, class(x)))))
        stop("not all arguments are text documents")

    structure(list(content = args,
                   meta = CorpusMeta(),
                   dmeta = data.frame(row.names = seq_along(args))),
              class = c("VCorpus", "Corpus"))
}

as.list.PCorpus <- as.list.VCorpus <-
function(x, ...)
    content(x)

content.VCorpus <-
function(x)
{
    if (!is.null(x$lazy))
        .Call(copyCorpus, x, materialize(x))
    x$content
}

content.PCorpus <-
function(x)
{
    db <- filehash::dbInit(x$dbcontrol[["dbName"]], x$dbcontrol[["dbType"]])
    filehash::dbMultiFetch(db, unlist(x$content))
}

length.PCorpus <- length.VCorpus <-
function(x)
    length(x$content)

print.PCorpus <- print.VCorpus <-
function(x, ...)
{
    cat(sprintf(ngettext(length(x),
                         "A corpus with %d text document\n\n",
                         "A corpus with %d text documents\n\n"),
                length(x)))

    meta <- meta(x, type = "corpus")
    dmeta <- meta(x, type = "indexed")

    cat("Metadata:\n")
    cat(sprintf("  Tag-value pairs. Tags: %s\n",
                paste(names(meta), collapse = " ")))
    cat("  Data frame. Variables:", colnames(dmeta), "\n")

    invisible(x)
}

inspect <-
function(x)
    UseMethod("inspect", x)
inspect.PCorpus <- inspect.VCorpus <-
function(x)
{
    print(x)
    cat("\n")
    print(noquote(content(x)))
    invisible(x)
}

writeCorpus <-
function(x, path = ".", filenames = NULL)
{
    filenames <- file.path(path,
      if (is.null(filenames))
          sprintf("%s.txt", as.character(meta(x, "id", "local")))
      else filenames)

    stopifnot(length(x) == length(filenames))

    mapply(function(doc, f) writeLines(as.character(doc), f), x, filenames)

    invisible(x)
}