docs: add project README

LICENSE

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+Mozilla Public License, version 2.0
+
+1. Definitions
+
+    1.1. “Contributor”
+    means each individual or legal entity that creates, contributes to the
+    creation of, or owns Covered Software.
+
+    1.2. “Contributor Version”
+    means the combination of the Contributions of others (if any) used by a
+    Contributor and that particular Contributor’s Contribution.
+
+    1.3. “Contribution”
+    means Covered Software of a particular Contributor.
+
+    1.4. “Covered Software”
+    means Source Code Form to which the initial Contributor has attached the
+    notice in Exhibit A, the Executable Form of such Source Code Form,
+    and Modifications of such Source Code Form, in each case
+    including portions thereof.
+
+    1.5. “Incompatible With Secondary Licenses”
+    means
+
+        a. that the initial Contributor has attached the notice described
+        in Exhibit B to the Covered Software; or
+
+        b. that the Covered Software was made available under the terms of
+        version 1.1 or earlier of the License, but not also under the terms
+        of a Secondary License.
+
+    1.6. “Executable Form”
+    means any form of the work other than Source Code Form.
+
+    1.7. “Larger Work”
+    means a work that combines Covered Software with other material,
+    in a separate file or files, that is not Covered Software.
+
+    1.8. “License”
+    means this document.
+
+    1.9. “Licensable”
+    means having the right to grant, to the maximum extent possible,
+    whether at the time of the initial grant or subsequently,
+    any and all of the rights conveyed by this License.
+
+    1.10. “Modifications”
+    means any of the following:
+
+        a. any file in Source Code Form that results from an addition to,
+        deletion from, or modification of the contents of Covered Software; or
+
+        b. any new file in Source Code Form that contains any Covered Software.
+
+    1.11. “Patent Claims” of a Contributor
+    means any patent claim(s), including without limitation, method, process,
+    and apparatus claims, in any patent Licensable by such Contributor that
+    would be infringed, but for the grant of the License, by the making,
+    using, selling, offering for sale, having made, import, or transfer of
+    either its Contributions or its Contributor Version.
+
+    1.12. “Secondary License”
+    means either the GNU General Public License, Version 2.0, the
+    GNU Lesser General Public License, Version 2.1, the GNU Affero General
+    Public License, Version 3.0, or any later versions of those licenses.
+
+    1.13. “Source Code Form”
+    means the form of the work preferred for making modifications.
+
+    1.14. “You” (or “Your”)
+    means an individual or a legal entity exercising rights under this License.
+    For legal entities, “You” includes any entity that controls,
+    is controlled by, or is under common control with You. For purposes of
+    this definition, “control” means (a) the power, direct or indirect,
+    to cause the direction or management of such entity, whether by contract
+    or otherwise, or (b) ownership of more than fifty percent (50%) of the
+    outstanding shares or beneficial ownership of such entity.
+
+2. License Grants and Conditions
+
+    2.1. Grants
+    Each Contributor hereby grants You a world-wide, royalty-free,
+    non-exclusive license:
+
+        a. under intellectual property rights (other than patent or trademark)
+        Licensable by such Contributor to use, reproduce, make available,
+        modify, display, perform, distribute, and otherwise exploit its
+        Contributions, either on an unmodified basis, with Modifications,
+        or as part of a Larger Work; and
+
+        b. under Patent Claims of such Contributor to make, use, sell,
+        offer for sale, have made, import, and otherwise transfer either
+        its Contributions or its Contributor Version.
+
+    2.2. Effective Date
+    The licenses granted in Section 2.1 with respect to any Contribution
+    become effective for each Contribution on the date the Contributor
+    first distributes such Contribution.
+
+    2.3. Limitations on Grant Scope
+    The licenses granted in this Section 2 are the only rights granted
+    under this License. No additional rights or licenses will be implied
+    from the distribution or licensing of Covered Software under this License.
+    Notwithstanding Section 2.1(b) above, no patent license is granted
+    by a Contributor:
+
+        a. for any code that a Contributor has removed from
+        Covered Software; or
+
+        b. for infringements caused by: (i) Your and any other third party’s
+        modifications of Covered Software, or (ii) the combination of its
+        Contributions with other software (except as part of its
+        Contributor Version); or
+
+        c. under Patent Claims infringed by Covered Software in the
+        absence of its Contributions.
+
+    This License does not grant any rights in the trademarks, service marks,
+    or logos of any Contributor (except as may be necessary to comply with
+    the notice requirements in Section 3.4).
+
+    2.4. Subsequent Licenses
+    No Contributor makes additional grants as a result of Your choice to
+    distribute the Covered Software under a subsequent version of this
+    License (see Section 10.2) or under the terms of a Secondary License
+    (if permitted under the terms of Section 3.3).
+
+    2.5. Representation
+    Each Contributor represents that the Contributor believes its
+    Contributions are its original creation(s) or it has sufficient rights
+    to grant the rights to its Contributions conveyed by this License.
+
+    2.6. Fair Use
+    This License is not intended to limit any rights You have under
+    applicable copyright doctrines of fair use, fair dealing,
+    or other equivalents.
+
+    2.7. Conditions
+    Sections 3.1, 3.2, 3.3, and 3.4 are conditions of the
+    licenses granted in Section 2.1.
+
+3. Responsibilities
+
+    3.1. Distribution of Source Form
+    All distribution of Covered Software in Source Code Form, including
+    any Modifications that You create or to which You contribute, must be
+    under the terms of this License. You must inform recipients that the
+    Source Code Form of the Covered Software is governed by the terms
+    of this License, and how they can obtain a copy of this License.
+    You may not attempt to alter or restrict the recipients’ rights
+    in the Source Code Form.
+
+    3.2. Distribution of Executable Form
+    If You distribute Covered Software in Executable Form then:
+
+        a. such Covered Software must also be made available in Source Code
+        Form, as described in Section 3.1, and You must inform recipients of
+        the Executable Form how they can obtain a copy of such Source Code
+        Form by reasonable means in a timely manner, at a charge no more than
+        the cost of distribution to the recipient; and
+
+        b. You may distribute such Executable Form under the terms of this
+        License, or sublicense it under different terms, provided that the
+        license for the Executable Form does not attempt to limit or alter
+        the recipients’ rights in the Source Code Form under this License.
+
+    3.3. Distribution of a Larger Work
+    You may create and distribute a Larger Work under terms of Your choice,
+    provided that You also comply with the requirements of this License for
+    the Covered Software. If the Larger Work is a combination of
+    Covered Software with a work governed by one or more Secondary Licenses,
+    and the Covered Software is not Incompatible With Secondary Licenses,
+    this License permits You to additionally distribute such Covered Software
+    under the terms of such Secondary License(s), so that the recipient of
+    the Larger Work may, at their option, further distribute the
+    Covered Software under the terms of either this License or such
+    Secondary License(s).
+
+    3.4. Notices
+    You may not remove or alter the substance of any license notices
+    (including copyright notices, patent notices, disclaimers of warranty,
+    or limitations of liability) contained within the Source Code Form of
+    the Covered Software, except that You may alter any license notices to
+    the extent required to remedy known factual inaccuracies.
+
+    3.5. Application of Additional Terms
+    You may choose to offer, and to charge a fee for, warranty, support,
+    indemnity or liability obligations to one or more recipients of
+    Covered Software. However, You may do so only on Your own behalf,
+    and not on behalf of any Contributor. You must make it absolutely clear
+    that any such warranty, support, indemnity, or liability obligation is
+    offered by You alone, and You hereby agree to indemnify every Contributor
+    for any liability incurred by such Contributor as a result of warranty,
+    support, indemnity or liability terms You offer. You may include
+    additional disclaimers of warranty and limitations of liability
+    specific to any jurisdiction.
+
+4. Inability to Comply Due to Statute or Regulation
+
+If it is impossible for You to comply with any of the terms of this License
+with respect to some or all of the Covered Software due to statute,
+judicial order, or regulation then You must: (a) comply with the terms of
+this License to the maximum extent possible; and (b) describe the limitations
+and the code they affect. Such description must be placed in a text file
+included with all distributions of the Covered Software under this License.
+Except to the extent prohibited by statute or regulation, such description
+must be sufficiently detailed for a recipient of ordinary skill
+to be able to understand it.
+
+5. Termination
+
+    5.1. The rights granted under this License will terminate automatically
+    if You fail to comply with any of its terms. However, if You become
+    compliant, then the rights granted under this License from a particular
+    Contributor are reinstated (a) provisionally, unless and until such
+    Contributor explicitly and finally terminates Your grants, and (b) on an
+    ongoing basis, if such Contributor fails to notify You of the
+    non-compliance by some reasonable means prior to 60 days after You have
+    come back into compliance. Moreover, Your grants from a particular
+    Contributor are reinstated on an ongoing basis if such Contributor
+    notifies You of the non-compliance by some reasonable means,
+    this is the first time You have received notice of non-compliance with
+    this License from such Contributor, and You become compliant prior to
+    30 days after Your receipt of the notice.
+
+    5.2. If You initiate litigation against any entity by asserting a patent
+    infringement claim (excluding declaratory judgment actions,
+    counter-claims, and cross-claims) alleging that a Contributor Version
+    directly or indirectly infringes any patent, then the rights granted
+    to You by any and all Contributors for the Covered Software under
+    Section 2.1 of this License shall terminate.
+
+    5.3. In the event of termination under Sections 5.1 or 5.2 above, all
+    end user license agreements (excluding distributors and resellers) which
+    have been validly granted by You or Your distributors under this License
+    prior to termination shall survive termination.
+
+6. Disclaimer of Warranty
+
+Covered Software is provided under this License on an “as is” basis, without
+warranty of any kind, either expressed, implied, or statutory, including,
+without limitation, warranties that the Covered Software is free of defects,
+merchantable, fit for a particular purpose or non-infringing. The entire risk
+as to the quality and performance of the Covered Software is with You.
+Should any Covered Software prove defective in any respect, You
+(not any Contributor) assume the cost of any necessary servicing, repair,
+or correction. This disclaimer of warranty constitutes an essential part of
+this License. No use of any Covered Software is authorized under this
+License except under this disclaimer.
+
+7. Limitation of Liability
+
+Under no circumstances and under no legal theory, whether tort
+(including negligence), contract, or otherwise, shall any Contributor, or
+anyone who distributes Covered Software as permitted above, be liable to
+You for any direct, indirect, special, incidental, or consequential damages
+of any character including, without limitation, damages for lost profits,
+loss of goodwill, work stoppage, computer failure or malfunction, or any and
+all other commercial damages or losses, even if such party shall have been
+informed of the possibility of such damages. This limitation of liability
+shall not apply to liability for death or personal injury resulting from
+such party’s negligence to the extent applicable law prohibits such
+limitation. Some jurisdictions do not allow the exclusion or limitation of
+incidental or consequential damages, so this exclusion and limitation may
+not apply to You.
+
+8. Litigation
+
+Any litigation relating to this License may be brought only in the courts of
+a jurisdiction where the defendant maintains its principal place of business
+and such litigation shall be governed by laws of that jurisdiction, without
+reference to its conflict-of-law provisions. Nothing in this Section shall
+prevent a party’s ability to bring cross-claims or counter-claims.
+
+9. Miscellaneous
+
+This License represents the complete agreement concerning the subject matter
+hereof. If any provision of this License is held to be unenforceable,
+such provision shall be reformed only to the extent necessary to make it
+enforceable. Any law or regulation which provides that the language of a
+contract shall be construed against the drafter shall not be used to construe
+this License against a Contributor.
+
+10. Versions of the License
+
+    10.1. New Versions
+    Mozilla Foundation is the license steward. Except as provided in
+    Section 10.3, no one other than the license steward has the right to
+    modify or publish new versions of this License. Each version will be
+    given a distinguishing version number.
+
+    10.2. Effect of New Versions
+    You may distribute the Covered Software under the terms of the version
+    of the License under which You originally received the Covered Software,
+    or under the terms of any subsequent version published
+    by the license steward.
+
+    10.3. Modified Versions
+    If you create software not governed by this License, and you want to
+    create a new license for such software, you may create and use a modified
+    version of this License if you rename the license and remove any
+    references to the name of the license steward (except to note that such
+    modified license differs from this License).
+
+    10.4. Distributing Source Code Form that is
+    Incompatible With Secondary Licenses
+    If You choose to distribute Source Code Form that is
+    Incompatible With Secondary Licenses under the terms of this version of
+    the License, the notice described in Exhibit B of this
+    License must be attached.
+
+Exhibit A - Source Code Form License Notice
+
+    This Source Code Form is subject to the terms of the
+    Mozilla Public License, v. 2.0. If a copy of the MPL was not distributed
+    with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+If it is not possible or desirable to put the notice in a particular file,
+then You may include the notice in a location (such as a LICENSE file in a
+relevant directory) where a recipient would be likely to
+look for such a notice.
+
+You may add additional accurate notices of copyright ownership.
+
+Exhibit B - “Incompatible With Secondary Licenses” Notice
+
+    This Source Code Form is “Incompatible With Secondary Licenses”,
+    as defined by the Mozilla Public License, v. 2.0.

README.md

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+# nff
+
+This is a high performance configuration parser and written in Rust. The goal is
+to receive possibly jumbled up nftables rule files, and output ✨ pretty ✨
+human readable output in return. The main emphasis is on the syntax-aware
+formatting with comprehensive grammar support. It is a future goal to allow
+editors to hook into nff in order to format your rulesets directly from your
+editor, or as a diagnostics source.
+
+## Features
+
+nff is in its early stages of development. While _most_ of the syntax is
+supported, I cannot guarantee that _everything_ is supported just yet.
+
+### Core Functionality
+
+- **Syntax-aware formatting** - Deep understanding of nftables grammar with
+  semantic preservation
+- **Multi-family support** - Handles `inet`, `ip`, `ip6`, `arp`, `bridge`, and
+  `netdev` table families
+- **Flexible indentation** - Configurable tabs/spaces with custom depth
+- **CIDR notation** - Proper handling of network addresses (`192.168.1.0/24`)
+- **Chain properties** - Hooks, priorities (including negative), policies,
+  device bindings
+
+### Advanced Features
+
+- **CST** - Lossless representation preserving all tokens
+- **Debug mode** - Comprehensive inspection of lexer tokens, AST, and CST
+- **Validation** - Syntax checking with precise error locations
+- **Optimization** - Configurable empty line reduction and whitespace control
+
+## Usage
+
+```bash
+# Basic formatting
+nff -f /etc/nftables.conf
+
+# Custom indentation (4 spaces)
+nff -f config.nft --indent spaces --spaces 4
+
+# Optimize formatting (reduce empty lines)
+nff -f config.nft --optimize
+
+# Output to file
+nff -f config.nft -o formatted.nft
+
+# Syntax validation only
+nff -f config.nft --check
+
+# Debug output for development (or debugging)
+nff -f config.nft --debug
+```
+
+## Architecture
+
+### Processing Pipeline
+
+nff implements a multi-stage pipeline:
+
+```mermaid
+graph TD
+    Input --> Lexer
+    Lexer --> Tokens
+    Lexer --> Parser
+    Tokens --> Parser
+    Parser --> CST
+    Parser --> AST
+    AST --> Formatter
+    Formatter --> Output
+    CST --> Formatter
+```
+
+## Installation
+
+Recommended way of installing nff is to use Nix.
+
+## Development
+
+### Testing
+
+```bash
+# Run test suite
+cargo test
+
+# Run with verbose output
+cargo test -- --nocapture
+
+# Test specific module
+cargo test lexer
+```
+
+### Code Quality
+
+```bash
+# Check compilation
+cargo check
+
+# Format code
+cargo fmt
+
+# Lint code
+cargo clippy
+
+# Check for unused dependencies
+cargo machete
+```
+
+## Supported nftables Features
+
+### Table Families
+
+- **inet** - Dual-stack IPv4/IPv6 (most common)
+- **ip** - IPv4 only
+- **ip6** - IPv6 only
+- **arp** - ARP protocol
+- **bridge** - Bridge/Layer 2
+- **netdev** - Network device (ingress/egress)
+
+### Chain Types & Hooks
+
+- **filter**: `input`, `forward`, `output`
+- **nat**: `prerouting`, `input`, `output`, `postrouting`
+- **route**: `output`
+- **security**: `input`, `forward`, `output`
+
+### Expression Types
+
+- **Protocol matching**: `ip protocol tcp`, `tcp dport 80`
+- **Interface matching**: `iifname "eth0"`, `oifname "wlan0"`
+- **Address matching**: `ip saddr 192.168.1.0/24`, `ip6 daddr ::1`
+- **Connection tracking**: `ct state established,related`
+- **Port specifications**: `tcp dport { 22, 80, 443 }`
+- **Rate limiting**: `limit rate 10/minute burst 5 packets`
+- **Sets and maps**: Named sets with timeout support
+
+### Actions & Statements
+
+- **Verdicts**: `accept`, `drop`, `reject`, `return`
+- **NAT**: `snat to 192.168.1.1`, `dnat to 192.168.1.100:80`
+- **Marking**: `mark set 0x1`, `ct mark set 0x1`
+- **Logging**: `log prefix "dropped: "`
+- **Counters**: `counter packets 0 bytes 0`
+
+## Examples
+
+### Basic Firewall
+
+Input (minified):
+
+```nftables
+table inet firewall{chain input{type filter hook input priority 0;policy drop;ct state established,related accept;iifname lo accept;tcp dport 22 accept}}
+```
+
+Output (formatted):
+
+```nftables
+#!/usr/sbin/nft -f
+table inet firewall {
+        chain input {
+                type filter hook input priority 0; policy drop;
+                ct state established,related accept
+                iifname lo accept
+                tcp dport 22 accept
+        }
+}
+```
+
+### NAT Configuration
+
+```nftables
+#!/usr/sbin/nft -f
+table ip nat {
+        chain prerouting {
+                type nat hook prerouting priority -100; policy accept;
+                iifname "eth0" tcp dport 80 dnat to 192.168.1.100:8080
+        }
+
+        chain postrouting {
+                type nat hook postrouting priority 100; policy accept;
+                oifname "eth0" masquerade
+        }
+}
+```
+
+### Rate Limiting
+
+```nftables
+#!/usr/sbin/nft -f
+table inet protection {
+        chain input {
+                type filter hook input priority 0; policy accept;
+                tcp dport 22 limit rate 5/minute burst 10 packets accept
+                tcp dport 22 drop
+        }
+}
+```
+
+## Contributing
+
+### Code Style
+
+- Follow `cargo fmt` formatting
+- Use `cargo clippy` recommendations
+- Maintain comprehensive documentation
+- Add tests for new features
+
+### Testing Strategy (WIP)
+
+- **Unit tests**: Individual component validation
+- **Integration tests**: End-to-end formatting verification
+- **Regression tests**: Known issue prevention
+- **Performance tests**: Benchmark critical paths
+
+### Building
+
+Build with `cargo build` as usual. If you are using Nix, you will also want to
+ensure that the Nix package builds as expected.
+
+## Technical Notes
+
+### CST Implementation
+
+The Concrete Syntax Tree (CST) preserves all source information including:
+
+- Whitespace and indentation
+- Comments and their positions
+- Token-level error recovery
+- Lossless round-trip formatting
+
+### Parser Architecture
+
+Below are the design goals of nff's architechture.
+
+- **Error recovery**: Continues parsing after syntax errors
+- **Incremental parsing**: Supports partial file processing
+- **Memory efficiency**: Streaming token processing where possible
+- **Grammar completeness**: Covers full nftables syntax specification
+
+## License
+
+nff is licensed under [MPL v2.0](LICENSE). See license file for more details on
+what the license entails.