{
  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"
          ];
        };

        # PostgreSQL 17 with PostGIS in the PostgreSQL extension path.
        postgresql = pkgs.postgresql_17.withPackages (
          ps: [
            ps.postgis
          ]
        );
      in
      {
        devShells.default = pkgs.mkShell {
          packages = [
            rust

            # PostgreSQL + PostGIS
            postgresql

            # SQLx migrations / CLI
            pkgs.sqlx-cli

            # GIS
            pkgs.gdal
            pkgs.geos
            pkgs.proj

            # Rust native dependencies
            pkgs.pkg-config
            pkgs.openssl
          ];

          shellHook = ''
            set -e

            # ============================================================
            # Environment
            # ============================================================

            export PGDATA="$PWD/.pgdata"
            export PGHOST="$PWD/.pgsocket"
            export PGDATABASE="county_sprints"
            export PGUSER="county_sprints"

            export RUST_BACKTRACE=1

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

            mkdir -p "$PGHOST"

            # Use an absolute path for the PostgreSQL Unix socket.
            PGHOST_ABS="$(cd "$PGHOST" && pwd)"

            # ============================================================
            # Initialise PostgreSQL cluster
            # ============================================================

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

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

            # ============================================================
            # Start PostgreSQL
            #
            # PostgreSQL is deliberately restricted to the Unix socket.
            # ============================================================

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

              pg_ctl \
                -D "$PGDATA" \
                -l "$PGDATA/postgresql.log" \
                -o "-c listen_addresses= -k $PGHOST_ABS" \
                start \
                >/dev/null
            fi

            # ============================================================
            # Wait until PostgreSQL is ready
            # ============================================================

            postgres_ready=0

            for _ in $(seq 1 50); do
              if pg_isready \
                -h "$PGHOST_ABS" \
                -U "$PGUSER" \
                >/dev/null 2>&1
              then
                postgres_ready=1
                break
              fi

              sleep 0.2
            done

            if [ "$postgres_ready" != "1" ]; then
              echo
              echo "ERROR: PostgreSQL could not be started."
              echo
              echo "PostgreSQL log:"
              echo "------------------------------------------------------------"

              if [ -f "$PGDATA/postgresql.log" ]; then
                cat "$PGDATA/postgresql.log"
              else
                echo "No PostgreSQL log found."
              fi

              echo "------------------------------------------------------------"
              echo

              return 1
            fi

            # ============================================================
            # Create application database
            # ============================================================

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

              createdb \
                -h "$PGHOST_ABS" \
                -U "$PGUSER" \
                "$PGDATABASE"
            fi

            # ============================================================
            # Enable PostGIS
            # ============================================================

            echo
            echo "==> Checking PostGIS"

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

            # ============================================================
            # SQLx / application connection string
            #
            # localhost is only the syntactic host. The host query
            # parameter tells libpq/SQLx to use our Unix socket.
            # ============================================================

            export DATABASE_URL="postgresql://$PGUSER@localhost/$PGDATABASE?host=$PGHOST_ABS"

            # ============================================================
            # Development information
            # ============================================================

            echo
            echo "============================================================"
            echo " Landkreis-Sprints development environment"
            echo "============================================================"
            echo
            echo "Rust:"
            echo "  $(rustc --version)"
            echo
            echo "PostgreSQL:"
            echo "  $(psql --version)"
            echo "  socket:    $PGHOST_ABS"
            echo "  database:  $PGDATABASE"
            echo "  user:      $PGUSER"
            echo
            echo "PostGIS:"

            psql \
              -h "$PGHOST_ABS" \
              -U "$PGUSER" \
              -d "$PGDATABASE" \
              -tAc "SELECT PostGIS_Full_Version();" |
              sed 's/^/  /'

            echo
            echo "DATABASE_URL:"
            echo "  $DATABASE_URL"
            echo
            echo "Commands:"
            echo "  sqlx migrate run"
            echo "  cargo check"
            echo "  cargo test"
            echo "  cargo run"
            echo
            echo "============================================================"
            echo
            set +e
          '';
        };
      }
    );
}