#!/bin/bash
# An incomplete script, more like notes really, for grabbing a
# copy of wiki.bash-hackers.org from archive.org

# This works by targeting pages that have been captured by the Wayback Machine 
# that specifically have '?do=edit' on the end of their URL.
# These pages present the original markdown source of the respective page.
# So with a little massaging, we should be able to extract said markdown.

# Where are we playing on the local file system?
basedir="${HOME}/git/wiki.bash-hackers.org"

# Prepend a string e.g.
# cmd: prepend foo bar
# out: foobar
# Also has a delimiter option e.g.
# cmd: prepend -d ';' foo bar
# out: foo;bar
prepend() {
    local _prepend_delimiter
    case "${1}" in
        (-d|--delimiter)
        _prepend_delimiter="${2}"
        shift 2
        ;;
    esac
    printf -- '%s\n' "${1}${_prepend_delimiter:-}${2}"
}

# Call archive.org's 'available' API to see if a site is available
# This will either return the URL of the most current snapshot, or null
# e.g.
# cmd: check_wayback_availability https://wiki.bash-hackers.org/howto/mutex?do=edit
# out: http://web.archive.org/web/20220615023742/https://wiki.bash-hackers.org/howto/mutex?do=edit
# vs
# cmd: check_wayback_availability https://contoso.com/pantsmcgee
# out: null
check_wayback_availability() {
    local remote_target
    remote_target="https://archive.org/wayback/available?url=${1:?No target specified}"
    curl -s -X GET "${remote_target}" | jq -r '.archived_snapshots.closest.url'
}

# Download the given target into a local file structure e.g.
# http://web.archive.org/web/20220706170849/https://wiki.bash-hackers.org/scripting/bashbehaviour?do=edit
# Will download into scripting/bashbehaviour
get_wayback_target() {
    local remote_target target_path target_dirname
    remote_target="${1:?No target specified}"
    # Strip out everything after 'bash-hackers.org' and '?do=edit' e.g.
    # http://web.archive.org/web/20220615023742/https://wiki.bash-hackers.org/howto/mutex?do=edit -> /howto/mutex
    target_path="$(sed -n 's/.*bash-hackers.org//p' <<< "${remote_target}" | sed -e 's/?do=edit//')"
    # Get the dirname e.g. /howto/mutex?do=edit -> /howto
    target_dirname="$(dirname "${target_path}")"
    # Create the path, ensuring that we strip the leading slash just-in-case e.g. /howto -> howto
    mkdir -p "${basedir:?FATAL - basedir unset}/${target_dirname/\//}"
    # Download the remote target to the local path
    curl -s -X GET "${remote_target}" | extract_markdown - > "./${target_path}.md"
}

# We want to pull internal-wiki links out of the markdown fragments.  These look like
# [[path:to:file]]
# But can be given friendly names like
# [[path:to:file | friendly name]]
# The friendly name might have leading spaces around the pipe char or not
# We start by grep'ing for '[['
# Then we filter out external links e.g. '[[http://contoso.com]]'
# Then we grep out just the link substrings
# Then we filter out friendly names (this could be brutally tidied up, it's late and I'm lazy right now)
# Then we append "/?do=edit/"
scrape_targets() {
    local source_file
    source_file="${1:?No target specified}"
    grep "\[\[" "${source_file}" |
        grep -v "\[\[http" |
        grep -o "\[\[.*\]\]" |
        sed -e 's/ | .*\]\]/]]/g' -e 's/| .*\]\]/]]/g' -e 's/|.*\]\]/]]/g' -e 's/\[\[/\//g' -e 's/\]\]/?do=edit/g' |
        tr ':' '/'
}

# Because of the structure of the downloaded files,
# we should be able to reliably extract our target markdown.
# First, remove everything between the first line and 'name="sectok"'
# Next, remove everything after '</textarea>'
# This should remove everything above and below our desired markdown
extract_markdown() {
    sed -e '1,/name="sectok"/d' -e '/<\/textarea>/,$d' "${1:-/dev/stdin}"
}

###### Beyond this point things get a little wishy-washy ######

(
    cd "${basedir}" || exit 1

    # If it's not already here, get the start page
    if [[ ! -f start ]]; then
        get_wayback_target https://web.archive.org/web/20220930131429/https://wiki.bash-hackers.org/start?do=edit
    fi

    # Extract a list of targets from the start page
    while read -r; do
        prepend "https://wiki.bash-hackers.org" "${REPLY}"
    done < <(scrape_targets start) > raw_targets

    # For each scraped target, validate that they're available from archive.org
    # and in doing so, generate a list of the urls for the latest captures of each
    while read -r; do
        check_wayback_availability "${REPLY}"
    done < raw_targets > waybacktargets

    # Work through each of the above urls
    while read -r; do
        get_wayback_target "${REPLY}"
    done < waybacktargets
)