# for usage see the example at the end

#' Parse xml records
#'
#' Creates a list of tibbles containing relevant information from all records
#' stored in the input directory.
#'
#' @param path character
#'
#' @export
read_all <- function(path="records/") {
    cat("Reading all records from", path, "\n")
    available_protocols <- list.files(path)
    res <- pblapply(available_protocols, read_one, path=path)

    lapply(res, `[[`, "redner") %>%
        bind_rows() %>%
        distinct() ->
        redner
    
    lapply(res, `[[`, "reden") %>%
        bind_rows() %>%
        distinct() ->
        reden

    lapply(res, `[[`, "talks") %>%
        bind_rows() %>%
        distinct() ->
        talks

    if (length(available_protocols) == 0)
        warning("The given directory is empty or does not exist.")
    list(redner = redner, reden = reden, talks = talks)
}

# this reads all currently parseable data from one xml
read_one <- function(name, path) {
    x <- tryCatch(read_xml(paste0(path, name)),
                  error = function(c) NULL)
    if (is.null(x)) return(NULL)
    cs <- xml_children(x)

    verlauf <- xml_find_first(x, "sitzungsverlauf")
    rednerl <- xml_find_first(x, "rednerliste")

    xml_children(rednerl) %>%
        parse_rednerliste() ->
        redner

    xml_children(verlauf) %>%
        xml_find_all("rede") %>%
        parse_redenliste() ->
        res

    list(redner = redner, reden = res$reden, talks = res$talks)
}

xml_get <- function(node, name) {
    res <- xml_text %$% xml_find_all(node, name)
    if (length(res) == 0) NA_character_
    else res
}

# parse one redner
parse_redner <- function(redner_xml) {
    redner_id <- xml_attr(redner_xml, "id")
    nm <- xml_child(redner_xml)
    vorname <- xml_get(nm, "vorname")
    nachname <- xml_get(nm, "nachname")
    fraktion <- xml_get(nm, "fraktion")
    titel <- xml_get(nm, "titel")
    rolle <- xml_find_all(nm, "rolle")
    if (length(rolle) > 0) {
        rolle_lang <- xml_get(rolle, "rolle_lang")
        rolle_kurz <- xml_get(rolle, "rolle_kurz")
    } else rolle_kurz <- rolle_lang <- NA_character_
    c(id = redner_id, vorname = vorname, nachname = nachname, fraktion = fraktion, titel = titel,
      rolle_kurz = rolle_kurz, rolle_lang = rolle_lang)
}

# parse one rede
# returns: - a rede (with rede id and redner id)
#          - all talks appearing in the rede (with corresponding content)
parse_rede <- function(rede_xml) {
    rede_id <- xml_attr(rede_xml, "id")
    cs <- xml_children(rede_xml)
    cur_redner <- NA_character_
    principal_redner <- NA_character_
    cur_content <- ""
    reden <- list()
    for (node in cs) {
        if (xml_name(node) == "p") {
            klasse <- xml_attr(node, "klasse")
            if (!is.na(klasse) && klasse == "redner") {
                if (!is.na(cur_redner)) {
                    rede <- c(rede_id = rede_id,
                              redner = cur_redner,
                              content = cur_content)
                    reden <- c(reden, list(rede))
                    cur_content <- ""
                } else {
                    principal_redner <- xml_child(node) %>% xml_attr("id")
                }
                cur_redner <- xml_child(node) %>% xml_attr("id")
            } else {
                cur_content <- paste0(cur_content, xml_text(node), sep="\n")
            }
        }
    }
    rede <- c(rede_id = rede_id,
              redner = cur_redner,
              content = cur_content)
    reden <- c(reden, list(rede))
    list(rede = c(id = rede_id, redner = principal_redner),
         parts = reden)
}

# creates a tibble of reden and a tibble of talks from a list of xml nodes representing reden
parse_redenliste <- function(redenliste_xml) {
    d <- sapply(redenliste_xml, parse_rede)
    reden <- simplify2array(d["rede", ])
    parts <- simplify2array %$% unlist(d["parts", ], recursive=FALSE)
    list(reden = tibble(id = reden["id",], redner = reden["redner",]),
         talks = tibble(rede_id = parts["rede_id", ],
                        redner = parts["redner", ],
                        content = parts["content", ]))
}

# create a tibble of redner from a list of xml nodes representing redner
parse_rednerliste <- function(rednerliste_xml) {
    d <- sapply(rednerliste_xml, parse_redner)
    tibble(id = d["id",],
           vorname = d["vorname",],
           nachname = d["nachname",],
           fraktion = d["fraktion",],
           titel = d["titel",],
           rolle_kurz = d["rolle_kurz",],
           rolle_lang = d["rolle_lang",])
}

# -------------------------------
# EXAMPLE USE

# make sure data ist downloaded via fetch.R
# res <- read_one("19126-data.xml")
# 
# res$redner
# res$reden
# res$talks

# -------------------------------