1 files changed, 231 insertions, 112 deletions

@@ -1,8 +1,9 @@
 #!/usr/bin/env bash
-# bollux: a bash gemini client
+################################################################################
+# BOLLUX: a bash gemini client
 # Author: Case Duckworth
 # License: MIT
-# Version: 0.4.0
+# Version: 0.4.1
 #
 # Commentary:
 #
@@ -46,6 +47,7 @@
 # [9]: OpenSSL `s_client' online manual
 #      https://www.openssl.org/docs/manmaster/man1/openssl-s_client.html
 #
+################################################################################
 # Code:
 
 # Program information
@@ -182,15 +184,31 @@ bollux_config() {
 
 # Initialize bollux state
 bollux_init() {
-        # Trap cleanup
+        # Trap `bollux_cleanup' on quit and exit
         trap bollux_cleanup INT QUIT EXIT
-        # State
-        REDIRECTS=0
+        # Trap `bollux_quit' on interrupt (C-c)
+        trap bollux_quit SIGINT
+
+        # Disable pathname expansion.
+        #
+        # It's very unlikely the user will want to navigate to a file when
+        # answering the GO prompt.
         set -f
+
+        # Initialize state
+        #
+        # Other than $REDIRECTS, bollux's mutable state includes
+        # $BOLLUX_URL, but that's initialized elsewhere (possibly even by
+        # the user)
+        REDIRECTS=0
+
         # History
+        #
+        # See also `history_append', `history_back', `history_forward'
         declare -a HISTORY # history is kept in an array
         HN=0               # position of history in the array
         run mkdir -p "${BOLLUX_HISTFILE%/*}"
+
         # Remove $BOLLUX_LESSKEY and re-generate keybindings (to catch rebinds)
         run rm -f "$BOLLUX_LESSKEY"
         mklesskey
@@ -206,12 +224,9 @@ bollux_cleanup() {
 #
 # The default message is from the wonderful show "Cowboy Bebop."
 bollux_quit() {
-        bollux_cleanup
         printf '\e[1m%s\e[0m:\t\e[3m%s\e[0m\n' "$PRGN" "$BOLLUX_BYEMSG"
         exit
 }
-# SIGINT is C-c, and I want to make sure bollux quits when it's typed.
-trap bollux_quit SIGINT
 
 # UTILITY FUNCTIONS ############################################################
 
@@ -221,11 +236,10 @@ trap bollux_quit SIGINT
 run() { # run COMMAND...
         # I have to add a `trap' here for SIGINT to work properly.
         trap bollux_quit SIGINT
-        log debug "$*"
+        LOG_FUNC=2 log debug "> $*"
         "$@"
 }
 
-
 # Log a message to stderr (&2).
 #
 # `log' in this script can take 3 different parameters: `d', `e', and `x', where
@@ -254,8 +268,8 @@ log() { # log LEVEL MESSAGE...
         esac
         shift
 
-        printf >&2 '\e[%sm%s:%s:\e[0m\t%s\n' \
-                   "$fmt" "$PRGN" "${FUNCNAME[1]}" "$*"
+        printf >&2 '\e[%sm%s:%-16s:\e[0m %s\n' \
+                   "$fmt" "$PRGN" "${FUNCNAME[${LOG_FUNC:-1}]}" "$*"
 }
 
 # Exit with an error and a message describing it.
@@ -341,12 +355,12 @@ sleep() { # sleep SECONDS
 
 # Normalize files.
 normalize() {
-        shopt -s extglob
+        shopt -s extglob # for the printf call below
         while IFS= read -r; do
                 # Normalize line endings to Unix-style (LF)
                 printf '%s\n' "${REPLY//$'\r'?($'\n')/}"
         done
-        shopt -u extglob
+        shopt -u extglob # reset 'extglob'
 }
 
 # URLS #########################################################################
@@ -367,16 +381,16 @@ normalize() {
 # trim whitespace.
 #
 # Useful for URLs that were probably input by humans.
-uwellform() {
-        local u="$1"
+uwellform() { # uwellform URL
+        local url="$1"
 
-        if [[ "$u" != *://* ]]; then
-                u="$BOLLUX_PROTO://$u"
+        if [[ "$url" != *://* ]]; then
+                url="$BOLLUX_PROTO://$url"
         fi
 
-        u="$(trim_string "$u")"
+        url="$(trim_string "$url")"
 
-        printf '%s\n' "$u"
+        printf '%s\n' "$url"
 }
 
 # Split a URL into its constituent parts, placing them all in the given array.
@@ -391,58 +405,94 @@ uwellform() {
 # takes the matched URL, splits it using the regex, then assigns each part to an
 # element of the url array NAME by using `printf -v', which prints to a
 # variable.
-usplit() { # usplit NAME:ARRAY URL:STRING
+usplit() { # usplit URL_ARRAY<name> URL
+        # Note: URL_ARRAY isn't assigned in `usplit', because it should
+        # already exist.  Pass /only/ the name of URL_ARRAY to this
+        # function, not its contents.
         local re='^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\?([^#]*))?(#(.*))?'
-        [[ $2 =~ $re ]] || return $?
+        local u="$2"
+        [[ "$u" =~ $re ]] || {
+                exit_code=$?
+                log error "usplit: '$2' doesn't match '$re'"
+                return $?
+        }
 
         # ShellCheck doesn't see that I'm using these variables in the `for'
         # loop below, because I'm not technically using them /as/ variables, but
         # as names to the variables.  The ${!c} formation in the `printf' call
         # below performs a reverse lookup on the name to get the actual data.
         # shellcheck disable=2034
-        local url="${BASH_REMATCH[0]}" \
-                scheme="${BASH_REMATCH[2]}" \
-                authority="${BASH_REMATCH[4]}" \
-                path="${BASH_REMATCH[5]}" \
-                query="${BASH_REMATCH[7]}" \
-                fragment="${BASH_REMATCH[9]}"
-
+        local entire_url="${BASH_REMATCH[0]}" \
+              scheme="${BASH_REMATCH[2]}" \
+              authority="${BASH_REMATCH[4]}" \
+              path="${BASH_REMATCH[5]}" \
+              query="${BASH_REMATCH[7]}" \
+              fragment="${BASH_REMATCH[9]}"
+
+        # Iterate through the 5 components of a URL and assign them to elements
+        # of URL_ARRAY, as follows:
         # 0=url 1=scheme 2=authority 3=path 4=query 5=fragment
-        local i=1 c
+        run printf -v "$1[0]" '%s' "$entire_url"
+        # This loop tests whether the component exists first -- if it
+        # doesn't, the special variable $UC_BLANK is used in the spot
+        # instead.  Bash doesn't have a useful way of differentiating an
+        # /unset/ element of an array, versus an /empty/ element.
+        # The only exception is that 'path' component, which always exists
+        # in a URL (I think the simplest URL possible is '/', the empty
+        # path).
+        local i=1 # begin at 1 -- the full URL is [0].
         for c in scheme authority path query fragment; do
                 if [[ "${!c}" || "$c" == path ]]; then
-                        printf -v "$1[$i]" '%s' "${!c}"
+                        run printf -v "$1[$i]" '%s' "${!c}"
                 else
-                        printf -v "$1[$i]" '%s' "$UC_BLANK"
+                        run printf -v "$1[$i]" '%s' "$UC_BLANK"
                 fi
                 ((i += 1))
         done
-        printf -v "$1[0]" '%s' "$url"
-}
 
-# Join a URL array (NAME) back into a string.
-ujoin() { # ujoin NAME:ARRAY
-        local -n U="$1"
+}
 
-        if ucdef U[1]; then
-                printf -v U[0] "%s:" "${U[1]}"
+# Join a URL array, split with `usplit', back into a string, assigning
+# it to the 0th element of the array.
+ujoin() { # ujoin URL_ARRAY<name>
+        # Here's the documentation for the '-n' flag:
+        #
+        # Give each name the nameref attribute, making it a name reference
+        # to another variable. That other variable is defined by the value of
+        # name. All references, assignments, and attribute modifications to
+        # name, except for those using or changing the -n attribute itself,
+        # are performed on the variable referenced by name's value. The
+        # nameref attribute cannot be applied to array variables.
+        #
+        # Pretty handy for passing-by-name!  Except that last part -- "The
+        # nameref attribute cannot be applied to array variables."  However,
+        # I've found a clever hack -- you can use 'printf -v' to print the
+        # value to the array element.
+        local -n URL_ARRAY="$1"
+
+        # For each possible URL component, check if it exists with `ucdef'.
+        # If it does, append it (with the correct component delimiter) to
+        # URL_ARRAY[0].
+        if ucdef URL_ARRAY[1]; then
+                printf -v URL_ARRAY[0] "%s:" "${URL_ARRAY[1]}"
         fi
 
-        if ucdef U[2]; then
-                printf -v U[0] "${U[0]}//%s" "${U[2]}"
+        if ucdef URL_ARRAY[2]; then
+                printf -v URL_ARRAY[0] "${URL_ARRAY[0]}//%s" "${URL_ARRAY[2]}"
         fi
 
-        printf -v U[0] "${U[0]}%s" "${U[3]}"
+        # The path component is required.
+        printf -v URL_ARRAY[0] "${URL_ARRAY[0]}%s" "${URL_ARRAY[3]}"
 
-        if ucdef U[4]; then
-                printf -v U[0] "${U[0]}?%s" "${U[4]}"
+        if ucdef URL_ARRAY[4]; then
+                printf -v URL_ARRAY[0] "${URL_ARRAY[0]}?%s" "${URL_ARRAY[4]}"
         fi
 
-        if ucdef U[5]; then
-                printf -v U[0] "${U[0]}#%s" "${U[5]}"
+        if ucdef URL_ARRAY[5]; then
+                printf -v URL_ARRAY[0] "${URL_ARRAY[0]}#%s" "${URL_ARRAY[5]}"
         fi
 
-        log d "${U[0]}"
+        log d "${URL_ARRAY[0]}"
 }
 
 # `ucdef' checks whether a URL component is blank or not -- if a component
@@ -451,26 +501,39 @@ ujoin() { # ujoin NAME:ARRAY
 # not going to really be in a URL).  I tried really hard to differentiate an
 # unset array element from a simply empty one, but like, as far as I could tell,
 # you can't do that in Bash.
-ucdef() { # ucdef NAME
-        [[ "${!1}" != "$UC_BLANK" ]]
+ucdef() { # ucdef COMPONENT<name>
+        local component="$1"
+        [[ "${!component}" != "$UC_BLANK" ]]
 }
 
 # `ucblank' determines whether a URL component is blank (""), as opposed to
 # undefined.
-ucblank() { # ucblank NAME
-        [[ -z "${!1}" ]]
+ucblank() { # ucblank COMPONENT<name>
+        local component="$1"
+        [[ -z "${!component}" ]]
 }
 
 # `ucset' sets one component of a URL array and setting the 0th element to the
 # new full URL.  Use it instead of directly setting the array element with U[x],
 # because U[0] will fall out of sync with the rest of the contents.
-ucset() { # ucset NAME VALUE
-        run eval "${1}='$2'"
-        run ujoin "${1/\[*\]/}"
+ucset() { # ucset URL_ARRAY_INDEX<name> NEW_VALUE
+        local url_array_component="$1" # Of form 'URL_ARRAY[INDEX]'
+        local value="$2"
+        
+        # Assign $value to $url_array_component.
+        #
+        # Wrapped in an 'eval' for the extra layer of indirection.
+        run eval "${url_array_component}='$value'"
+
+        # Rejoin the URL_ARRAY with the changed value.
+        #
+        # The substitution here strips the array index subscript (i.e.,
+        # URL[4] => URL), passing the name of the full array to `ujoin'.
+        run ujoin "${url_array_component/\[*\]/}"
 }
 
-# [1]: encode a URL using percent-encoding.
-uencode() { # uencode URL:STRING
+# [1]: Encode a URL using percent-encoding.
+uencode() { # uencode URL
         local LC_ALL=C
         for ((i = 0; i < ${#1}; i++)); do
                 : "${1:i:1}"
@@ -482,14 +545,14 @@ uencode() { # uencode URL:STRING
         printf '\n'
 }
 
-# [1]: decode a percent-encoded URL.
-udecode() { # udecode URL:STRING
+# [1]: Decode a percent-encoded URL.
+udecode() { # udecode URL
         : "${1//+/ }"
         printf '%b\n' "${_//%/\\x}"
 }
 
-# Implement [2] § 5.2.4, "Remove Dot Segments"
-pundot() { # pundot PATH:STRING
+# Implement [2]: 5.2.4, "Remove Dot Segments".
+pundot() { # pundot PATH
         local input="$1"
         local output
         while [[ "$input" ]]; do
@@ -512,28 +575,28 @@ pundot() { # pundot PATH:STRING
         printf '%s\n' "${output//\/\//\//}"
 }
 
-# Implement [2] § 5.2.3, "Merge Paths"
-pmerge() { # pmerge BASE:ARRAY REFERENCE:ARRAY
-        local -n b="$1"
-        local -n r="$2"
+# Implement [2] Section 5.2.3, "Merge Paths".
+pmerge() { # pmerge BASE_PATH<name> REFERENCE_PATH<name>
+        local -n base_path="$1"
+        local -n reference_path="$2"
 
-        if ucblank r[3]; then
-                printf '%s\n' "${b[3]//\/\//\//}"
+        if ucblank reference_path[3]; then
+                printf '%s\n' "${base_path[3]//\/\//\//}"
                 return
         fi
 
-        if ucdef b[2] && ucblank b[3]; then
-                printf '/%s\n' "${r[3]//\/\//\//}"
+        if ucdef base_path[2] && ucblank base_path[3]; then
+                printf '/%s\n' "${reference_path[3]//\/\//\//}"
         else
                 local bp=""
-                if [[ "${b[3]}" == */* ]]; then
-                        bp="${b[3]%/*}"
+                if [[ "${base_path[3]}" == */* ]]; then
+                        bp="${base_path[3]%/*}"
                 fi
-                printf '%s/%s\n' "${bp%/}" "${r[3]#/}"
+                printf '%s/%s\n' "${bp%/}" "${reference_path[3]#/}"
         fi
 }
 
-# `utransform' implements [2]6 § 5.2.2, "Transform Resources."
+# `utransform' implements [2]6 Section 5.2.2, "Transform Resources."
 #
 # That section conveniently lays out a pseudocode algorithm describing how URL
 # resources should be transformed from one to another.  This function just
@@ -609,19 +672,21 @@ utransform() {   # utransform TARGET:ARRAY BASE:STRING REFERENCE:STRING
 #
 ################################################################################
 
-# Request a resource from a gemini server - see [3] §§ 2, 4.
+# Request a resource from a gemini server - see [3] Sections 2, 4.
 gemini_request() { # gemini_request URL
         local -a url
-        usplit url "$1"
+        run usplit url "$1"
+        log debug "${url[@]}"
 
         # Remove user info from the URL.
         #
         # URLs can technically be of the form <proto>://<user>:<pass>@<domain>
-        # (see [2], § 3.2, "Authority").  I don't know of any Gemini servers
+        # (see [2] Section 3.2, "Authority").  I don't know of any Gemini servers
         # that use the <user> or <pass> parts, so `gemini_request' just strips
         # them from the requested URL.  This will need to be changed if servers
         # decide to use this method of authentication.
-        ucset url[2] "${url[2]#*@}"
+        log debug "Removing user info from the URL"
+        run ucset url[2] "${url[2]#*@}"
 
         # Determine the port to request.
         #
@@ -630,6 +695,7 @@ gemini_request() { # gemini_request URL
         # port can be specified after the domain, separated with a colon.  The
         # user can also request a different default port, for whatever reason,
         # by setting the variable $BOLLUX_GEMINI_PORT.
+        log debug "Determining the port to request"
         local port
         if [[ "${url[2]}" == *:* ]]; then
                 port="${url[2]#*:}"
@@ -665,7 +731,7 @@ gemini_request() { # gemini_request URL
         run "${ssl_cmd[@]}" <<<"$url"
 }
 
-# Handle the gemini response - see [3] § 3.
+# Handle the gemini response - see [3] Section 3.
 gemini_response() { # gemini_response URL
         local code meta # received on the first line of the response
         local title     # determined by a clunky heuristic, see read loop: (2*)
@@ -685,12 +751,12 @@ gemini_response() { # gemini_response URL
         # `download', below), but I'm not sure how to remedy that issue either.
         # It requires more research.
         while read -t "$BOLLUX_TIMEOUT" -r code meta ||
-                { (($? > 128)) && die 99 "Timeout."; }; do
+                        { (($? > 128)) && die 99 "Timeout."; }; do
                 break
         done
         log d "[$code] $meta"
 
-        # Branch depending on the status code.  See [3], Appendix 1.
+        # Branch depending on the status code.  See [3] Appendix 1.
         #
         # Notes:
         # - All codes other than 3* (Redirects) reset the REDIRECTS counter.
@@ -720,7 +786,7 @@ gemini_response() { # gemini_response URL
                 #
                 # This while loop reads through the file looking for a line
                 # starting with `#', which is a level-one heading in text/gemini
-                # (see [3], § 5).  It assumes that the first such heading is the
+                # (see [3] Section 5).  It assumes that the first such heading is the
                 # title of the page, and uses that title for the terminal title
                 # and for the history.
                 local pretitle
@@ -756,7 +822,7 @@ gemini_response() { # gemini_response URL
                 # distinction.  I'm not sure what the difference would be in
                 # practice, anyway.
                 #
-                # Per [4], bollux limits the number of redirects a page is
+                # Per [4] bollux limits the number of redirects a page is
                 # allowed to make (by default, five).  Change `$BOLLUX_MAXREDIR'
                 # to customize that limit.
                 ((REDIRECTS += 1))
@@ -773,7 +839,7 @@ gemini_response() { # gemini_response URL
                 run blastoff "$meta" # TODO: confirm redirect
                 ;;
         (4*) # TEMPORARY ERROR
-                # Since the 4* codes ([3], Appendix 1) are all server issues,
+                # Since the 4* codes ([3] Appendix 1) are all server issues,
                 # bollux can treat them all basically the same.  This is an area
                 # that could use some expansion.
                 local desc="Temporary error"
@@ -847,7 +913,7 @@ gemini_response() { # gemini_response URL
 gopher_request() { # gopher_request URL
         local url="$1"
 
-        # [7] § 2.1
+        # [7] Section 2.1
         [[ "$url" =~ gopher://([^/?#:]*)(:([0-9]+))?(/((.))?(/?.*))?$ ]]
         local server="${BASH_REMATCH[1]}" \
               port="${BASH_REMATCH[3]:-$BOLLUX_GOPHER_PORT}" \
@@ -866,7 +932,7 @@ gopher_request() { # gopher_request URL
 # Handle a server response.
 gopher_response() { # gopher_response URL
         local url="$1" pre=false
-        # [7] § 2.1
+        # [7] Section 2.1
         #
         # Note that this duplicates the code in `gopher_request'.  There might
         # be a good way to thread this data through so that it's not computed
@@ -881,7 +947,7 @@ gopher_response() { # gopher_response URL
         # basically, each line in a gophermap starts with a character, its type,
         # and then is followed by a series of tab-separated fields describing
         # where that type is and how to display it.  The full list of original
-        # line types can be found in [6] § 3.8, though the types have also been
+        # line types can be found in [6] Section 3.8, though the types have also been
         # extended over the years.  Since bollux can only display types that are
         # text-ish, it only concerns itself with those in this case statement.
         # All the others are simply downloaded.
@@ -915,7 +981,7 @@ gopher_response() { # gopher_response URL
                 fi
                 ;;
         (*) # Anything else
-                # The list at [6] § 3.8 includes the following (noted where it
+                # The list at [6] Section 3.8 includes the following (noted where it
                 # might be good to differently handle them in the future):
                 #
                 # 2. Item is a CSO phone-book server            *****
@@ -940,7 +1006,7 @@ gopher_response() { # gopher_response URL
 
 # Convert a gophermap naively to a gemini page.
 #
-# Based strongly on [8], but bash-ified.  Due to the properties of link lines in
+# Based strongly on [8] but bash-ified.  Due to the properties of link lines in
 # gemini, many of the item types in `gemini_reponse' can be linked to the proper
 # protocol handlers here -- so if a user is trying to reach a TCP link through
 # gopher, bollux won't have to handle it, for example.*
@@ -998,7 +1064,7 @@ gopher_convert() {
                                 pre=false
                         fi
                         printf '=> telnet://%s:%s/%s%s %s\n' \
-                                "$server" "$port" "$type" "$path" "$label"
+                               "$server" "$port" "$type" "$path" "$label"
                         ;;
                 (*) # other type
                         if $pre; then
@@ -1006,7 +1072,7 @@ gopher_convert() {
                                 pre=false
                         fi
                         printf '=> gopher://%s:%s/%s%s %s\n' \
-                                "$server" "$port" "$type" "$path" "$label"
+                               "$server" "$port" "$type" "$path" "$label"
                         ;;
                 esac
         done
@@ -1028,7 +1094,8 @@ gopher_convert() {
 # display the fetched content
 display() { # display METADATA [TITLE]
         local -a less_cmd
-        local i mime charset
+        local mime charset
+
         # split header line
         local -a hdr
         IFS=';' read -ra hdr <<<"$1"
@@ -1178,7 +1245,7 @@ typeset_gemini() {
                                 ;;
                         (alt | both)
                                 $pre && PRE_LINE_FORCE=true \
-                                        gemini_pre "${REPLY#\`\`\`}"
+                                                      gemini_pre "${REPLY#\`\`\`}"
                                 ;;
                         esac
                         continue
@@ -1215,13 +1282,13 @@ gemini_link() {
                 printf "\e[${C_SIGIL}m%${S_MARGIN}s ${C_RESET}" "$s"
                 printf "\e[${C_LINK_NUMBER}m[%d]${C_RESET} " "$ln"
                 fold_line -n -B "\e[${C_LINK_TITLE}m" -A "${C_RESET}" \
-                        -l "$((${#ln} + 3))" -m "${T_MARGIN}" \
-                        "$WIDTH" "$(trim_string "$t")"
+                          -l "$((${#ln} + 3))" -m "${T_MARGIN}" \
+                          "$WIDTH" "$(trim_string "$t")"
                 fold_line -B " \e[${C_LINK_URL}m" \
-                        -A "${C_RESET}" \
-                        -l "$((${#ln} + 3 + ${#t}))" \
-                        -m "$((T_MARGIN + ${#ln} + 2))" \
-                        "$WIDTH" "$a"
+                          -A "${C_RESET}" \
+                          -l "$((${#ln} + 3 + ${#t}))" \
+                          -m "$((T_MARGIN + ${#ln} + 2))" \
+                          "$WIDTH" "$a"
         else
                 gemini_pre "$1"
         fi
@@ -1239,7 +1306,7 @@ gemini_header() {
 
                 printf "\e[${C_SIGIL}m%${S_MARGIN}s ${C_RESET}" "$s"
                 fold_line -B "\e[${hdrfmt}m" -A "${C_RESET}" -m "${T_MARGIN}" \
-                        "$WIDTH" "$t"
+                          "$WIDTH" "$t"
         else
                 gemini_pre "$1"
         fi
@@ -1254,7 +1321,7 @@ gemini_list() {
 
                 printf "\e[${C_SIGIL}m%${S_MARGIN}s ${C_RESET}" "$s"
                 fold_line -B "\e[${C_LIST}m" -A "${C_RESET}" -m "$T_MARGIN" \
-                        "$WIDTH" "$t"
+                          "$WIDTH" "$t"
         else
                 gemini_pre "$1"
         fi
@@ -1269,7 +1336,7 @@ gemini_quote() {
 
                 printf "\e[${C_SIGIL}m%${S_MARGIN}s ${C_RESET}" "$s"
                 fold_line -B "\e[${C_QUOTE}m" -A "${C_RESET}" -m "$T_MARGIN" \
-                        "$WIDTH" "$t"
+                          "$WIDTH" "$t"
         else
                 gemini_pre "$1"
         fi
@@ -1279,7 +1346,7 @@ gemini_text() {
         if ! ${2-false}; then
                 printf "%${S_MARGIN}s " ' '
                 fold_line -m "$T_MARGIN" \
-                        "$WIDTH" "$1"
+                          "$WIDTH" "$1"
         else
                 gemini_pre "$1"
         fi
@@ -1432,7 +1499,19 @@ extract_links() {
         done
 }
 
-# download $BOLLUX_URL
+# Download a file.
+#
+# Any non-otherwise-handled MIME type will be downloaded using this function.
+# It uses 'dd' to download the resource to a temporary file, then attempts to
+# move it to $BOLLUX_DOWNDIR (by default, $PWD).  If that's not possible (either
+# because the target file already exists or the 'mv' invocation fails for some
+# reason), `download' logs the error and alerts the user where the temporary
+# file is saved.
+#
+# `download' works by reading the end of the pipe from `display', which means
+# that sometimes, due to something with the way bash or while or ... something
+# ... chunks the data, sometimes binary data gets corrupted.  This is an area
+# that requires more research.
 download() {
         tn="$(mktemp)"
         log x "Downloading: '$BOLLUX_URL' => '$tn'..."
@@ -1447,35 +1526,67 @@ download() {
         fi
 }
 
-# append a URL to history
+# HISTORY #####################################################################
+#
+# While bollux saves history to a file ($BOLLUX_HISTFILE), it doesn't /do/
+# anything with the history that's been saved.  When I do implement the history
+# functionality, it'll probably be on top of a file:// protocol, which will make
+# it very simple to also implement bookmarks and the previewing of pages.  In
+# fact, I should be able to implement this change by the weekend (2021-03-07).
+#
+###############################################################################
+
+# Append a URL to history.
 history_append() { # history_append URL TITLE
-        BOLLUX_URL="$1"
-        # date/time, url, title (best guess)
-        run printf '%(%FT%T)T\t%s\t%s\n' -1 "$1" "$2" >>"$BOLLUX_HISTFILE"
-        HISTORY[$HN]="$BOLLUX_URL"
+        local url="$1"
+        local title="$2"
+
+        # Print the URL and its title (if given) to $BOLLUX_HISTFILE.
+        local fmt=''
+        fmt+='%(%FT%T)T\t'      # %(_)T calls directly to 'strftime'.
+        if (( $# == 2 )); then
+                fmt+='%s\t'     # $url
+                fmt+='%s\n'     # $title
+        else
+                fmt+='%s%s\n'   # printf needs a field for every argument.
+        fi
+        run printf -- "$fmt" -1 "$url" "$title" >>"$BOLLUX_HISTFILE"
+
+        # Add the URL to the HISTORY array and increment the pointer.
+        HISTORY[$HN]="$url"
         ((HN += 1))
+
+        # Update $BOLLUX_URL.
+        BOLLUX_URL="$url"
 }
 
-# move back in history (session)
+# Move back in session history.
 history_back() {
         log d "HN=$HN"
+        # We need to subtract 2 from HN because it automatically increases by
+        # one with each call to `history_append'.  If we subtract 1, we'll just
+        # be at the end of the array again, reloading the page.
         ((HN -= 2))
+        
         if ((HN < 0)); then
                 HN=0
                 log e "Beginning of history."
                 return 1
         fi
+        
         run blastoff "${HISTORY[$HN]}"
 }
 
-# move forward in history (session)
+# Move forward in session history.
 history_forward() {
         log d "HN=$HN"
+        
         if ((HN >= ${#HISTORY[@]})); then
                 HN="${#HISTORY[@]}"
                 log e "End of history."
                 return 1
         fi
+        
         run blastoff "${HISTORY[$HN]}"
 }
 
@@ -1499,7 +1610,7 @@ blastoff() { # blastoff [-u] URL
         fi
 
         # After ensuring the URL is well-formed, `blastoff' needs to transform
-        # it according to the transform rules of RFC 3986 (see §5.2.2), which
+        # it according to the transform rules of RFC 3986 (see Section 5.2.2), which
         # turns relative references into absolute references that bollux can use
         # in its request to the server.  That's followed by a check that the
         # protocol is set, defaulting to Gemini if it isn't.
@@ -1535,13 +1646,21 @@ blastoff() { # blastoff [-u] URL
                         run "${url[1]}_response" "$url"
                 else
                         log d \
-                                "No response handler for '${url[1]}';" \
-                                " passing thru"
+                            "No response handler for '${url[1]}';" \
+                            " passing thru"
                         passthru
                 fi
         }
 }
 
+# $BASH_SOURCE is an array that stores the "stack" of source calls in bash.  If
+# the first element of that array is "bollux", that means the user called this
+# script, instead of sourcing it.  In that case, and ONLY in that case, should
+# bollux actually enter the main loop of the program.  Otherwise, allow the
+# sourcing environment to simply source this script.
+#
+# This is basically the equivalent of python's 'if __name__ == "__main__":'
+# block.
 if [[ "${BASH_SOURCE[0]}" == "$0" ]]; then
         ${DEBUG:-false} && set -x
         run bollux "$@"