Initial commit

.drone.yml

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+kind: pipeline
+name: default
+type: exec
+
+steps:
+  - name: build
+    commands:
+      - nix-build
+
+node:
+  nix: 1

.envrc

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+use nix

.gitignore

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+/site
+/result*

default.nix

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+let
+  sources = import ./nix/sources.nix;
+  pkgs = import sources.nixpkgs {};
+  inherit (import sources.gitignore { inherit (pkgs) lib; }) gitignoreSource;
+
+  stdenv = pkgs.stdenv;
+
+  python3Packages = pkgs.python3Packages;
+  buildPythonPackage = python3Packages.buildPythonPackage;
+  fetchPypi = python3Packages.fetchPypi;
+
+  lunr = buildPythonPackage rec {
+    pname = "lunr";
+    version = "0.5.8";
+
+    src = fetchPypi {
+      inherit pname version;
+      sha256 = "0vn2j5iyy40sv0f4v8nin5n5xs4a020g6gcbcgfpbxzgk0xhdyy4";
+    };
+
+    propagatedBuildInputs = with python3Packages; [
+      future
+      six
+    ];
+
+    checkInputs = with python3Packages; [
+      mock
+      pytest
+    ];
+  };
+
+  # FIXME: use nixpkgs’s mkdocs once it is ≥1.1
+  mkdocs = buildPythonPackage rec {
+    pname = "mkdocs";
+    version = "1.1.2";
+
+    src = fetchPypi {
+      inherit pname version;
+      sha256 = "0fgv5zawpyyv0vd4j5y8m4h058lh9jkwfcm0xy4pg7dr09a1xdph";
+    };
+
+    propagatedBuildInputs = (with python3Packages; [
+      backports_tempfile
+      click
+      jinja2
+      livereload
+      markdown
+      nltk
+      pyyaml
+      tornado
+    ]) ++ [
+      lunr
+    ];
+
+    doCheck = false; # circular depdendency
+  };
+
+  pymdown-extensions = buildPythonPackage rec {
+    pname = "pymdown-extensions";
+    version = "8.0.1";
+
+    src = fetchPypi {
+      inherit pname version;
+      sha256 = "07p5xks6qf73nbv0qb7jrspkpmxdyr7dpxv3rnkh9p2b5l2h99wv";
+    };
+
+    propagatedBuildInputs = with python3Packages; [
+      markdown
+    ];
+
+    doCheck = false; # they fail?
+  };
+
+  mkdocs-material-extensions = buildPythonPackage rec {
+    pname = "mkdocs-material-extensions";
+    version = "1.0.1";
+
+    src = fetchPypi {
+      inherit pname version;
+      sha256 = "13y617sql4hqs376c3dfcb6v7q41km9x7fh52k3f74a2brzzniv9";
+    };
+
+    # circular dependency
+    doCheck = false;
+    postPatch = ''
+      sed -i 's/mkdocs-material>=5.0.0//' requirements/project.txt
+    '';
+  };
+
+  mkdocs-material = buildPythonPackage rec {
+    pname = "mkdocs-material";
+    version = "6.1.2";
+
+    src = fetchPypi {
+      inherit pname version;
+      sha256 = "0yifc1df94rsaxy72hqnhjkv4c50c30j5kg0yxybkxy07p7kafic";
+    };
+
+    propagatedBuildInputs = (with python3Packages; [
+      markdown
+      pygments
+    ]) ++ [
+      mkdocs
+      mkdocs-material-extensions
+      pymdown-extensions
+    ];
+  };
+
+  iosevka-web = stdenv.mkDerivation rec {
+    pname = "iosevka-web";
+    version = "3.7.1";
+
+    src = pkgs.fetchzip {
+      url = "https://github.com/be5invis/Iosevka/releases/download/v${version}/pkg-iosevka-${version}.zip";
+      sha256 = "0d012aqfnyqlpl4smfa2x2qz2qmbbfxb6jr4awv8gp6r359rc9k1";
+      stripRoot = false;
+    };
+
+    dontBuild = true;
+
+    installPhase = ''
+      mkdir -p $out
+      cp -r woff woff2 ttf *.css $out
+    '';
+  };
+in
+stdenv.mkDerivation {
+  name = "wiki";
+
+  src = gitignoreSource ./.;
+
+  buildPhase = "mkdocs build";
+
+  installPhase = ''
+    cp -r site $out
+    mkdir -p $out/assets/fonts
+    ln -s ${iosevka-web} $out/assets/fonts/iosevka
+  '';
+
+  nativeBuildInputs = [
+    mkdocs
+    mkdocs-material
+  ];
+}

docs/data.md

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+# Data
+
+## Aria2
+
+### Get list of all connected peers
+
+    :::shell
+    curl -s -X POST -d '{"jsonrpc": "2.0", "id": "", "method": "aria2.tellActive"}' http://localhost:6800/jsonrpc | jq -r '.result[].gid' | while read gid;do echo $gid; curl -s -X POST -d '{"jsonrpc": "2.0", "id": "", "method": "aria2.getPeers", "params": ["'"$gid"'"]}' http://localhost:6800/jsonrpc | jq -r '.result[].ip'; done

docs/hostnames.md

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+# Hostname Candidates
+
+| name | relation | special field |
+| ---- | -------- | ------------- |
+| ayu | <https://anidb.net/character/7909> | |
+| shibazaki | <https://anidb.net/character/67927> | |
+| maaa | <https://madeinabyss.fandom.com/wiki/Maaa> | |
+| vueko | <https://madeinabyss.fandom.com/wiki/Vueko> | |
+
+## In use
+
+These once were candidates and are now in use. Might be recycled once the
+system is no longer in use.
+
+| name | relation | special field |
+| ---- | -------- | ------------- |
+| sayuri | <https://anidb.net/ch7914> | |
+| renge | <https://anidb.net/character/57473> | |
+
+## Host Group names
+
+| name | relation | special field |
+| ---- | -------- | ------------- |
+| shinonome | Shinonome Labs from [Nichijou](https://anidb.net/anime/8168) | lab |

docs/index.md

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+# Main Page
+
+Mostly uncommented ugly code snippets (most are shell for linux commandline and
+some are javascript for browser console). It is possible (almost certain) that
+some won’t work because I last used them three years ago. So, use at your own
+risk.

docs/kobo.md

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+# Kobo
+
+## Links
+
+ * Installation without registration: <https://yingtongli.me/blog/2018/07/30/kobo-rego.html>
+ * Access root telnet shell: <https://yingtongli.me/blog/2018/07/30/kobo-telnet.html>
+ * Install dropbear (sshd): <https://yingtongli.me/blog/2018/07/30/kobo-ssh.html>
+
+## Enable telnet without modifying the rootfs
+
+Edit `.kobo/Kobo/Kobo eReader.conf` on the filesystem available via USB:
+
+    [DeveloperSettings]
+    EnableDebugServices=true
+
+## Enable dropbear sshd
+
+Copy `dropbearmulti` to `/opt/dropbear/dropbearmulti`.
+
+In `/opt/dropbear/`:
+
+    ./dropbearmulti dropbearkey -t dss -f dss_key
+    ./dropbearmulti dropbearkey -t rsa -f rsa_key
+    ./dropbearmulti dropbearkey -t ecdsa -f ecdsa_key
+
+Add authorized keys to `/.ssh/authorized_keys`
+
+Link scp: `ln -s /opt/dropbear/dropbearmulti /usr/bin/scp`
+
+Add to `/etc/inittab`:
+
+    ::IGNORE THIS LINE, it is just here to not confuse mkdocs
+    ::respawn:/opt/dropbear/dropbearmulti dropbear -s -F -E -r /opt/dropbear/dss_key -r /opt/dropbear/rsa_key -r /opt/dropbear/ecdsa_key
+
+!!! note
+    After a system update, it might be necessary to repeat this step.
+
+## Re-scan the library
+
+Useful after adding a book via ssh.
+
+    :::shell
+    ssh root@kobo-address 'echo -e "usb plug add\nusb plug remove" >> /tmp/nickel-hardware-status'

docs/media/index.md

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+# Media (General)
+
+## Audio
+
+### Split file with cue sheet and use filename from cue sheet
+
+    :::shell
+    shnsplit -D -f file.cue -t "%n %t" -o "flac flac -8 -o %f -" file.flac
+
+### Remove all tags except MusicBrainz tags from flac files
+
+    :::shell
+    for i in *.flac; do tags=$(metaflac --export-tags-to=- $i | grep -E '^MUSICBRAINZ_'); metaflac --remove-all-tags $i; metaflac --import-tags-from=- $i <<< $tags; done
+
+### Downmix 5.1 to 2.0
+
+    :::shell
+    sox in.wav out.wav remix -m 1v0.3694,3v0.2612,5v0.3694 2v0.3694,3v0.2612,6v0.3694 norm
+
+### Record pulseaudio device to flac
+
+    :::shell
+    parec [ -d DEVICE ] | flac --endian=little --channels=2 --bps=16 --sample-rate=48000 --sign=signed -o foo.flac -
+
+## Video
+
+### Copy DVD stream to file [with dvd already copied to local directory]
+
+    :::shell
+    mpv --stream-dump=1.mkv dvd://1 [--dvd-device path/to/dvd]
+
+## MKV
+
+### Fix mimetype of font attachments
+
+Some matroska files have the mimetype for font attachment for fonts set to
+`application/octet-strem`.
+
+    :::shell
+     mkvpropedit --attachment-mime-type font/sfnt --update-attachment mime-type:application/octet-stream file.mkv
+
+## FFmpeg
+
+### Create color timeline image from video
+
+    :::shell
+    (infile=in.mkv; outfile=out.png; rows=320; width=1920; height=1080; ffmpeg -i $infile -vf tblend=all_mode=average,fps=${rows}/$(ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 $infile),scale=1:1,scale=${width}/${rows}:${height},setsar=1,tile=${rows}x1 -frames:v 1 $outfile)
+
+### Show duration of file in seconds
+
+    :::shell
+    ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 file.mkv
+
+### Remove EIA-608 subtitles from video bitstream
+
+([source](https://stackoverflow.com/a/51439554))
+
+    :::shell
+    ffmpeg -i infile.mkv -c copy -bsf:v "filter_units=remove_types=6" outfile.mkv
+
+## QP file
+
+replace 24/1.001 with framerate
+
+    :::shell
+    ffprobe -i infile.mkv -print_format json -show_chapters -loglevel error | jq -r '.chapters[].start / 1000000000 * 24/1.001 | round | tostring + " I"' >> foo.qp
+
+## Manga
+
+### Convert greyscale images to actuual greyscale
+
+For some reasons, many releases encode greyscale manga pages as yuv420. Sadly,
+the chroma layers are not completely empty but include some (almost invisible)
+noise. This fixes that for lower battery comsumption, a really small file size
+gain and just because it seems right.
+
+This only works for pages with the same size (image2/ffmpeg limitation), but
+releases suffering from this mostly fulfill this requirement.
+
+**WARNING**: This uses some heuristics (SSIM > 98) to determine if a page is
+greyscale. This may not work all the time (it did for me though). Please verify
+if all converted images actually are greyscale.
+
+    :::shell
+    ffmpeg -loglevel error -f lavfi -i "movie=%03d.jpg:f=image2,split=2[orig][in2];[in2]extractplanes=y[grey];[orig][grey]ssim=-" -f null - >> ssim
+    while read frame;do (( $(cut -d' ' -f5 <<< $frame | cut -c 7-8) < 98 )) || {file=$(printf "%03d.jpg\n" $(cut -d' ' -f1 <<< $frame|cut -d: -f2)); echo $file; jpegtran -copy none -optimize -grayscale -outfile $file $file}; done < ssim
+    jpegoptim -s *.jpg
+    exiftool -overwrite_original -all= *.jpg
+
+    # print all converted images for verification
+    grep -E 'All:0.(9[0-8]|[0-8][0-9])' ssim
+
+
+### Merge page spreads to single page
+
+Use function `merge_pages right-page left-page` (without .jpg). Result will be
+written to left-page-right-page.jpg`.
+
+    :::shell
+    function merge_pages() {
+        convert ${2}.jpg ${1}.jpg +append ${1}-${2}.jpg
+        exiftool -overwrite_original -all= ${1}-${2}.jpg
+    }
+
+    # remove single pages
+    mkdir single_pages
+    for i in ???-???.jpg;do mv $(cut -d- -f1 <<< $i).jpg $(cut -d- -f2 <<< $i) single_pages;done
+
+## mpv
+
+### View thumbnails generated by [mpv-gallery-view](https://github.com/occivink/mpv-gallery-view)
+
+    :::shell
+    mpv --pause --demuxer=rawvideo --demuxer-rawvideo-mp-format=bgra --demuxer-rawvideo-w=288 --demuxer-rawvideo-h=162 FILE
+
+Convert to tiles
+
+    :::shell
+    ffmpeg -codec:v rawvideo -pixel_format bgra -video_size 288:162 -f image2 -pattern_type glob -i '*' -vf tile=layout=10x10 tile-%04d.png
+
+## Download
+
+### Bilibili live recording
+
+    :::shell
+    curl 'https://api.live.bilibili.com/xlive/web-room/v1/record/getLiveRecordUrl?rid=R1sx411c7Xn&platform=html5'|jq -r '.data.list | map(.url) | to_entries[] | .value + "\n  out=" + (.key|tostring) + ".flv"' | aria2c --auto-file-renaming=false -x 16 -j 10 -i -
+    mkvmerge '[' $(find . -name '*.flv'|sort -V) ']' -o merge.mkv
+
+## PDF
+
+### Downsample bitmap PDF
+
+Useful for sending large 300/600 dpi scans as e-mail. Change `pdfimage32` to
+`pdfimage8` for greyscale, `300` to the input DPI and `DownScaleFactor` to the
+desired downscaling. For some reason fails when setting compression to JPEG.
+
+    :::shell
+    gs -sDEVICE=pdfimage24 -r300 -dDownScaleFactor=2 -o downscaled.pdf document.pdf
+
+Imagemagick supports JPEG. Set your desired output density and JPEG quality.
+
+    :::shell
+    convert -density 300 -compress jpeg -quality 80 document.pdf downscaled.pdf

docs/media/vapoursynth.md

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+# Vapoursynth
+
+## Limit memory usage
+
+    :::python3
+    core.max_cache_size = 1000
+
+## Basic encoding options for 10 bit
+
+### x265
+
+x265 only outputs to its own bistream format.
+
+    :::shell
+    vapoursynth sh -c 'vspipe --y4m script.vpy - | x265 --y4m -D 10 --preset slow --crf 18 -o output.265 -'
+
+### x264
+
+Unlike x265, x264 supports mkv containers as output.
+
+    :::shell
+    vapoursynth sh -c 'vspipe --y4m script.vpy - | x264 --demuxer y4m --profile high10 --input-depth 10 --output-depth 10 --preset slow --crf 18 -o output.mkv -'

docs/nix.md

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+# Nix(OS)
+
+## List dependencies of package
+
+    nix-store -q --references `which bash`
+
+Instead of <code>\`which bash\`</code> you can also specify a file in a
+nix store path (or just the store path) or a link to contents of the store.
+
+### Reverse dependencies
+
+    nix-store -q --referrers `which bash`
+
+Analogue to `apt-cache rdepends`. Like with `--references`, any nix store
+reference can be passed.
+
+### Recursive dependencies
+
+    nix-store -qR `which man`
+
+In tree view:
+
+    nix-store -q --tree `which man`
+
+## List all system generations
+
+    sudo nix-env --list-generations --profile /nix/var/nix/profiles/system
+
+## Build package outside of nixpkgs tree
+
+    nix-build -E 'with import <nixpkgs> { }; callPackage ./mypackage.nix { }'

docs/sysop.md

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+# Sysop
+
+## Prometheus
+
+### Reload config
+
+    :::shell
+    curl -X POST -u simon:$(pass sbruder.de/prometheus|head -n1) https://prometheus.sbruder.de/-/reload
+
+### Remove certain time range from Prometheus
+
+Requires [TSDB Admin APIs to be
+enabled](https://prometheus.io/docs/prometheus/latest/querying/api/#tsdb-admin-apis)
+(`--web.enable-admin-api`)
+
+    :::shell
+    curl -u user:pass -X POST -g 'https://prometheus-endpoint/api/v1/admin/tsdb/delete_series?match[]=metric{label="foo"}&start=TIMESTAMP&end=TIMESTAMP
+
+## OpenSSL
+
+### Get certificate expiry date
+
+    :::shell
+    openssl s_client -connect hostname:443 2>& /dev/null <<< '' | openssl x509 -noout -dates
+
+    # starttls
+    openssl s_client -connect hostname:587 -starttls smtp 2>& /dev/null <<< '' | openssl x509 -noout -dates
+
+## Docker
+
+### List images by size
+
+    :::shell
+    docker image ls --format "table {{.Size}}\t{{.Repository}}:{{.Tag}}\t{{.ID}}"|sort -h
+
+### Enable IPv6 NAT
+
+Makes no sense on first and second thought, but after a while it seems like the
+right thing.
+
+`/etc/docker/daemon.json`:
+
+    :::json
+    {
+      "ipv6": true,
+      "fixed-cidr-v6": "fd00:d0ce:d0ce:d0ce::/64"
+    }
+
+<!--
+This is the right way, but since I did not get `netfilter-persistent` to work,
+I have to use iptables.
+
+    :::shell
+    nft add table ip6 nat
+    nft add chain ip6 nat postrouting \{ type nat hook postrouting priority 100 \; \}
+    nft add rule ip6 nat postrouting ip6 saddr fd00:d0ce:d0ce:d0ce::/64 masquerade
+-->
+
+    :::shell
+    ip6tables -t nat -A POSTROUTING -s fd00:d0ce:d0ce:d0ce::/64 -j MASQUERADE
+    ip6tables-save > /etc/iptables/rules.v6
+
+Publishing a port will still use the userland proxy. If you do not want this,
+have a look at <https://github.com/robbertkl/docker-ipv6nat>.
+
+    :::shell
+    docker run -d --restart=always -v /var/run/docker.sock:/var/run/docker.sock:ro --cap-drop=ALL --cap-add=NET_RAW --cap-add=NET_ADMIN --cap-add=SYS_MODULE --net=host robbertkl/ipv6nat
+
+## Misc
+
+### Add swap file
+
+    :::shell
+    fallocate -l 1G /swapfile
+    chmod 600 /swapfile
+    mkswap /swapfile
+    swapon /swapfile

docs/web-services.md

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+# Web Services
+
+## General
+
+### Remove query string from downloaded files
+
+    :::shell
+    for i in *\?*; do echo mv "$i" "$(echo $i | cut -d'?' -f 1)"; done
+
+## Mora
+
+### Get title listing (for MusicBrainz)
+
+    :::js
+    [...document.querySelectorAll('.package_table tr')].map(el => {try {return `${el.querySelector('.package_td1').innerText} ${el.querySelector('.package_td2').innerText} ／ ${el.querySelector('.package_td3').innerText} ${el.querySelector('.package_td4').innerText.split('\n')[0]}`} catch(e) {}}).slice(1).join('\n')
+
+## Instagram
+
+### Download picture in highest quality available
+
+    https://instagram.com/p/SHORTCODE/media/?size=l
+
+## Bandcamp
+
+### Get title listing (for MusicBrainz)
+
+    :::js
+    [...document.querySelectorAll('#track_table .track_row_view')].map(el => `${el.querySelector('.track_number').innerText} ${el.querySelector('.track-title').innerText} (${el.querySelector('.time').innerText})`).join("\n")
+
+## Ototoy
+
+### Get title listing (for MusicBrainz)
+
+    :::js
+    Array.from(document.querySelectorAll('#tracklist tr:not(:nth-child(1))')).map(el => el.querySelector('span[id^="title-"]').innerText + " " + el.querySelector('td:nth-child(3)').innerText).join("\n")

mkdocs.yml

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+site_name: Wiki
+
+theme:
+  name: material
+  custom_dir: theme
+
+markdown_extensions:
+  - codehilite
+  - admonition
+  - toc:
+      permalink: true

nix/sources.json

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+{
+    "gitignore": {
+        "branch": "master",
+        "description": "Nix function for filtering local git sources",
+        "homepage": "",
+        "owner": "hercules-ci",
+        "repo": "gitignore",
+        "rev": "c4662e662462e7bf3c2a968483478a665d00e717",
+        "sha256": "1npnx0h6bd0d7ql93ka7azhj40zgjp815fw2r6smg8ch9p7mzdlx",
+        "type": "tarball",
+        "url": "https://github.com/hercules-ci/gitignore/archive/c4662e662462e7bf3c2a968483478a665d00e717.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "nixpkgs": {
+        "branch": "nixos-unstable",
+        "description": "Nix Packages collection",
+        "homepage": "",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "34ad166a830d3ac1541dcce571c52231f2f0865a",
+        "sha256": "1jvi1562x3kq65w642vfimpszv65zbc7c2nv8gakhzcx4n3f47xq",
+        "type": "tarball",
+        "url": "https://github.com/NixOS/nixpkgs/archive/34ad166a830d3ac1541dcce571c52231f2f0865a.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    }
+}

nix/sources.nix

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+# This file has been generated by Niv.
+
+let
+
+  #
+  # The fetchers. fetch_<type> fetches specs of type <type>.
+  #
+
+  fetch_file = pkgs: spec:
+    if spec.builtin or true then
+      builtins_fetchurl { inherit (spec) url sha256; }
+    else
+      pkgs.fetchurl { inherit (spec) url sha256; };
+
+  fetch_tarball = pkgs: name: spec:
+    let
+      ok = str: ! builtins.isNull (builtins.match "[a-zA-Z0-9+-._?=]" str);
+      # sanitize the name, though nix will still fail if name starts with period
+      name' = stringAsChars (x: if ! ok x then "-" else x) "${name}-src";
+    in
+      if spec.builtin or true then
+        builtins_fetchTarball { name = name'; inherit (spec) url sha256; }
+      else
+        pkgs.fetchzip { name = name'; inherit (spec) url sha256; };
+
+  fetch_git = spec:
+    builtins.fetchGit { url = spec.repo; inherit (spec) rev ref; };
+
+  fetch_local = spec: spec.path;
+
+  fetch_builtin-tarball = name: throw
+    ''[${name}] The niv type "builtin-tarball" is deprecated. You should instead use `builtin = true`.
+        $ niv modify ${name} -a type=tarball -a builtin=true'';
+
+  fetch_builtin-url = name: throw
+    ''[${name}] The niv type "builtin-url" will soon be deprecated. You should instead use `builtin = true`.
+        $ niv modify ${name} -a type=file -a builtin=true'';
+
+  #
+  # Various helpers
+  #
+
+  # The set of packages used when specs are fetched using non-builtins.
+  mkPkgs = sources:
+    let
+      sourcesNixpkgs =
+        import (builtins_fetchTarball { inherit (sources.nixpkgs) url sha256; }) {};
+      hasNixpkgsPath = builtins.any (x: x.prefix == "nixpkgs") builtins.nixPath;
+      hasThisAsNixpkgsPath = <nixpkgs> == ./.;
+    in
+      if builtins.hasAttr "nixpkgs" sources
+      then sourcesNixpkgs
+      else if hasNixpkgsPath && ! hasThisAsNixpkgsPath then
+        import <nixpkgs> {}
+      else
+        abort
+          ''
+            Please specify either <nixpkgs> (through -I or NIX_PATH=nixpkgs=...) or
+            add a package called "nixpkgs" to your sources.json.
+          '';
+
+  # The actual fetching function.
+  fetch = pkgs: name: spec:
+
+    if ! builtins.hasAttr "type" spec then
+      abort "ERROR: niv spec ${name} does not have a 'type' attribute"
+    else if spec.type == "file" then fetch_file pkgs spec
+    else if spec.type == "tarball" then fetch_tarball pkgs name spec
+    else if spec.type == "git" then fetch_git spec
+    else if spec.type == "local" then fetch_local spec
+    else if spec.type == "builtin-tarball" then fetch_builtin-tarball name
+    else if spec.type == "builtin-url" then fetch_builtin-url name
+    else
+      abort "ERROR: niv spec ${name} has unknown type ${builtins.toJSON spec.type}";
+
+  # If the environment variable NIV_OVERRIDE_${name} is set, then use
+  # the path directly as opposed to the fetched source.
+  replace = name: drv:
+    let
+      saneName = stringAsChars (c: if isNull (builtins.match "[a-zA-Z0-9]" c) then "_" else c) name;
+      ersatz = builtins.getEnv "NIV_OVERRIDE_${saneName}";
+    in
+      if ersatz == "" then drv else ersatz;
+
+  # Ports of functions for older nix versions
+
+  # a Nix version of mapAttrs if the built-in doesn't exist
+  mapAttrs = builtins.mapAttrs or (
+    f: set: with builtins;
+    listToAttrs (map (attr: { name = attr; value = f attr set.${attr}; }) (attrNames set))
+  );
+
+  # https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/lists.nix#L295
+  range = first: last: if first > last then [] else builtins.genList (n: first + n) (last - first + 1);
+
+  # https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/strings.nix#L257
+  stringToCharacters = s: map (p: builtins.substring p 1 s) (range 0 (builtins.stringLength s - 1));
+
+  # https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/strings.nix#L269
+  stringAsChars = f: s: concatStrings (map f (stringToCharacters s));
+  concatStrings = builtins.concatStringsSep "";
+
+  # fetchTarball version that is compatible between all the versions of Nix
+  builtins_fetchTarball = { url, name, sha256 }@attrs:
+    let
+      inherit (builtins) lessThan nixVersion fetchTarball;
+    in
+      if lessThan nixVersion "1.12" then
+        fetchTarball { inherit name url; }
+      else
+        fetchTarball attrs;
+
+  # fetchurl version that is compatible between all the versions of Nix
+  builtins_fetchurl = { url, sha256 }@attrs:
+    let
+      inherit (builtins) lessThan nixVersion fetchurl;
+    in
+      if lessThan nixVersion "1.12" then
+        fetchurl { inherit url; }
+      else
+        fetchurl attrs;
+
+  # Create the final "sources" from the config
+  mkSources = config:
+    mapAttrs (
+      name: spec:
+        if builtins.hasAttr "outPath" spec
+        then abort
+          "The values in sources.json should not have an 'outPath' attribute"
+        else
+          spec // { outPath = replace name (fetch config.pkgs name spec); }
+    ) config.sources;
+
+  # The "config" used by the fetchers
+  mkConfig =
+    { sourcesFile ? if builtins.pathExists ./sources.json then ./sources.json else null
+    , sources ? if isNull sourcesFile then {} else builtins.fromJSON (builtins.readFile sourcesFile)
+    , pkgs ? mkPkgs sources
+    }: rec {
+      # The sources, i.e. the attribute set of spec name to spec
+      inherit sources;
+
+      # The "pkgs" (evaluated nixpkgs) to use for e.g. non-builtin fetchers
+      inherit pkgs;
+    };
+
+in
+mkSources (mkConfig {}) // { __functor = _: settings: mkSources (mkConfig settings); }

shell.nix

@@ -0,0 +1 @@
+import ./default.nix

theme/main.html

@@ -0,0 +1,13 @@
+{% extends "base.html" %}
+
+{% block fonts %}
+<link rel="stylesheet" href="{{ 'assets/fonts/iosevka/iosevka.css' | url }}">
+<style>
+  body, input {
+    font-family: "Roboto", -apple-system, BlinkMacSystemFont, Helvetica, Arial, sans-serif;
+  }
+  code, kbd, pre {
+    font-family: "Iosevka Web", monospace;
+  }
+</style>
+{% endblock %}