{
  description = "Landkreis-Sprints";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    rust-overlay.url = "github:oxalica/rust-overlay";
    flake-utils.url = "github:numtide/flake-utils";
  };

  outputs = {
    nixpkgs,
    rust-overlay,
    flake-utils,
    ...
  }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = import nixpkgs {
          inherit system;

          overlays = [
            rust-overlay.overlays.default
          ];
        };

        rust = pkgs.rust-bin.stable.latest.default.override {
          extensions = [
            "rustfmt"
            "clippy"
          ];
        };
      in
      {
        devShells.default = pkgs.mkShell {
          packages = with pkgs; [
            rust

            # Database
            postgresql
            postgresqlPackages.postgis
            sqlx-cli

            # GIS
            gdal
            geos
            proj

            # Build dependencies
            pkg-config
            openssl
          ];

          shellHook = ''
            set -e

            # ------------------------------------------------------------
            # Local PostgreSQL
            # ------------------------------------------------------------

            export PGDATA="$PWD/.pgdata"
            export PGHOST="$PWD/.pgsocket"
            export PGPORT="5433"

            export PGDATABASE="county_sprints"
            export PGUSER="county_sprints"

            mkdir -p "$PGHOST"

            # ------------------------------------------------------------
            # Initialise PostgreSQL cluster
            # ------------------------------------------------------------

            if [ ! -f "$PGDATA/PG_VERSION" ]; then
              echo
              echo "==> Initialising local PostgreSQL cluster"

              initdb \
                --auth=trust \
                --no-locale \
                --encoding=UTF8 \
                "$PGDATA" \
                >/dev/null
            fi

            # ------------------------------------------------------------
            # Configure PostgreSQL
            # ------------------------------------------------------------

            # Always write our development settings. This means changing
            # the flake also updates an already existing local cluster.
            cat > "$PGDATA/postgresql.conf" <<EOF
listen_addresses = '' + "''" + ''
port = 5433
unix_socket_directories = '$PGHOST'
EOF

            # ------------------------------------------------------------
            # Start PostgreSQL
            # ------------------------------------------------------------

            if ! pg_ctl \
              -D "$PGDATA" \
              status \
              >/dev/null 2>&1
            then
              echo
              echo "==> Starting local PostgreSQL"

              pg_ctl \
                -D "$PGDATA" \
                -o "-k $PGHOST -p $PGPORT" \
                -l "$PGDATA/postgresql.log" \
                start \
                >/dev/null

              # Wait until PostgreSQL actually accepts connections.
              for i in $(seq 1 30); do
                if pg_isready \
                  -h "$PGHOST" \
                  -p "$PGPORT" \
                  >/dev/null 2>&1
                then
                  break
                fi

                sleep 0.2
              done
            fi

            # ------------------------------------------------------------
            # Create application role
            # ------------------------------------------------------------

            if ! psql \
              -h "$PGHOST" \
              -p "$PGPORT" \
              -d postgres \
              -tAc \
              "SELECT 1
                 FROM pg_roles
                WHERE rolname = '$PGUSER'" |
              grep -q 1
            then
              echo
              echo "==> Creating PostgreSQL role '$PGUSER'"

              psql \
                -h "$PGHOST" \
                -p "$PGPORT" \
                -d postgres \
                -v ON_ERROR_STOP=1 \
                -c \
                "CREATE ROLE \"$PGUSER\" LOGIN;"
            fi

            # ------------------------------------------------------------
            # Create application database
            # ------------------------------------------------------------

            if ! psql \
              -h "$PGHOST" \
              -p "$PGPORT" \
              -d postgres \
              -tAc \
              "SELECT 1
                 FROM pg_database
                WHERE datname = '$PGDATABASE'" |
              grep -q 1
            then
              echo
              echo "==> Creating PostgreSQL database '$PGDATABASE'"

              psql \
                -h "$PGHOST" \
                -p "$PGPORT" \
                -d postgres \
                -v ON_ERROR_STOP=1 \
                -c \
                "CREATE DATABASE \"$PGDATABASE\" OWNER \"$PGUSER\";"
            fi

            # ------------------------------------------------------------
            # Make sure the application role owns the database
            # ------------------------------------------------------------

            psql \
              -h "$PGHOST" \
              -p "$PGPORT" \
              -d postgres \
              -v ON_ERROR_STOP=1 \
              -c \
              "ALTER DATABASE \"$PGDATABASE\" OWNER TO \"$PGUSER\";" \
              >/dev/null

            # ------------------------------------------------------------
            # PostGIS
            # ------------------------------------------------------------

            echo
            echo "==> Checking PostGIS"

            psql \
              -h "$PGHOST" \
              -p "$PGPORT" \
              -d "$PGDATABASE" \
              -v ON_ERROR_STOP=1 \
              -c \
              "CREATE EXTENSION IF NOT EXISTS postgis;" \
              >/dev/null

            # ------------------------------------------------------------
            # DATABASE_URL for sqlx / application
            # ------------------------------------------------------------

            export DATABASE_URL="postgresql://$PGUSER@/$PGDATABASE?host=$PGHOST&port=$PGPORT"

            # ------------------------------------------------------------
            # Environment
            # ------------------------------------------------------------

            export RUST_BACKTRACE=1

            if [ -z "''${RUST_LOG:-}" ]; then
              export RUST_LOG="info"
            fi

            # ------------------------------------------------------------
            # Info
            # ------------------------------------------------------------

            echo
            echo "=============================================="
            echo " Landkreis-Sprints development environment"
            echo "=============================================="
            echo
            echo "Rust:"
            rustc --version
            echo
            echo "PostgreSQL:"
            psql \
              -h "$PGHOST" \
              -p "$PGPORT" \
              -d "$PGDATABASE" \
              -tAc "SELECT version();" |
              sed 's/^/  /'
            echo
            echo "PostGIS:"
            psql \
              -h "$PGHOST" \
              -p "$PGPORT" \
              -d "$PGDATABASE" \
              -tAc "SELECT PostGIS_Full_Version();" |
              sed 's/^/  /'
            echo
            echo "DATABASE_URL:"
            echo "  $DATABASE_URL"
            echo
            echo "Run:"
            echo "  sqlx migrate run"
            echo "  cargo test"
            echo "  cargo run"
            echo
          '';
        };
      }
    );
}