// Copyright 2024 The NativeLink Authors. All rights reserved.

//

// Licensed under the Functional Source License, Version 1.1, Apache 2.0 Future License (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//    See LICENSE file for details

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

use core::convert::AsRef;

use std::borrow::Cow;

use nativelink_error::{Error, ResultExt, error_if, make_input_err};

use tonic::Code;

const ERROR_MSG: &str = concat!(

    "Expected resource_name to be of pattern ",

    "'{?instance_name/}(?uploads/{uuid}/)blobs/{?/digest_function}{/hash}/{size}{?/optional_metadata}' or ",

    "'{?instance_name/}(?uploads/{uuid}/)compressed-blobs{?/compressor}{?/digest_function}{/hash}/{size}{?/optional_metadata}'",

);

const COMPRESSORS: [&str; 4] = ["identity", "zstd", "deflate", "brotli"];

const DIGEST_FUNCTIONS: [&str; 9] = [

    "sha256",

    "sha1",

    "md5",

    "vso",

    "sha384",

    "sha512",

    "murmur3",

    "sha256tree",

    "blake3",

];

// Named struct to make the code easier to read when adding the slash size.

const SLASH_SIZE: usize = 1;

// Rules are as follows:

//

// "instance_name" may contain slashes and may contain or equal "uploads", "compressed-blobs" and "blobs".

// if is_upload is false:

// {instance_name}/               compressed-blobs/{compressor}/{digest_function/}{hash}/{size}{/optional_metadata}

// {instance_name}/               compressed-blobs/{compressor}/{digest_function/}{hash}/{size}

// {instance_name}/               blobs/                        {digest_function/}{hash}/{size}{/optional_metadata}

// {instance_name}/               blobs/                        {digest_function/}{hash}/{size}

//                                compressed-blobs/{compressor}/{digest_function/}{hash}/{size}{/optional_metadata}

//                                compressed-blobs/{compressor}/{digest_function/}{hash}/{size}

//                                blobs/                        {digest_function/}{hash}/{size}{/optional_metadata}

//                                blobs/                        {digest_function/}{hash}/{size}

// {instance_name}/               compressed-blobs/{compressor}/                  {hash}/{size}{/optional_metadata}

// {instance_name}/               compressed-blobs/{compressor}/                  {hash}/{size}

// {instance_name}/               blobs/                                          {hash}/{size}{/optional_metadata}

// {instance_name}/               blobs/                                          {hash}/{size}

//                                compressed-blobs/{compressor}/                  {hash}/{size}{/optional_metadata}

//                                compressed-blobs/{compressor}/                  {hash}/{size}

//

//                                blobs/                                          {hash}/{size}{/optional_metadata}

//                                blobs/                                          {hash}/{size}

//

// if is_upload is true:

// {instance_name}/uploads/{uuid}/compressed-blobs/{compressor}/{digest_function/}{hash}/{size}{/optional_metadata}

// {instance_name}/uploads/{uuid}/compressed-blobs/{compressor}/{digest_function/}{hash}/{size}

// {instance_name}/uploads/{uuid}/blobs/                        {digest_function/}{hash}/{size}{/optional_metadata}

// {instance_name}/uploads/{uuid}/blobs/                        {digest_function/}{hash}/{size}

//                 uploads/{uuid}/compressed-blobs/{compressor}/{digest_function/}{hash}/{size}{/optional_metadata}

//                 uploads/{uuid}/compressed-blobs/{compressor}/{digest_function/}{hash}/{size}

//                 uploads/{uuid}/blobs/                        {digest_function/}{hash}/{size}{/optional_metadata}

//                 uploads/{uuid}/blobs/                        {digest_function/}{hash}/{size}

// {instance_name}/uploads/{uuid}/compressed-blobs/{compressor}/                  {hash}/{size}{/optional_metadata}

// {instance_name}/uploads/{uuid}/compressed-blobs/{compressor}/                  {hash}/{size}

// {instance_name}/uploads/{uuid}/blobs/                                          {hash}/{size}{/optional_metadata}

// {instance_name}/uploads/{uuid}/blobs/                                          {hash}/{size}

//                 uploads/{uuid}/compressed-blobs/{compressor}/                  {hash}/{size}{/optional_metadata}

//                 uploads/{uuid}/compressed-blobs/{compressor}/                  {hash}/{size}

//                 uploads/{uuid}/blobs/                                          {hash}/{size}{/optional_metadata}

//                 uploads/{uuid}/blobs/                                          {hash}/{size}

//

// Useful utility struct for converting bazel's (uri-like path) into its parts.

#[derive(Debug, Default)]

pub struct ResourceInfo<'a> {

    pub instance_name: Cow<'a, str>,

    pub uuid: Option<Cow<'a, str>>,

    pub compressor: Option<Cow<'a, str>>,

    pub digest_function: Option<Cow<'a, str>>,

    pub hash: Cow<'a, str>,

    size: Cow<'a, str>,

    pub expected_size: usize,

    pub optional_metadata: Option<Cow<'a, str>>,

}

impl<'a> ResourceInfo<'a> {

    pub fn new(resource_name: &'a str, is_upload: bool) -> Result<Self, Error> {

        // The most amount of slashes there can be to get to "(compressed-)blobs" section is 7.

        let mut rparts = resource_name.rsplitn(7, '/');

        let mut output = ResourceInfo::default();

        let mut end_bytes_processed = 0;

        let 
end_state63
 = recursive_parse(

            &mut rparts,

            &mut output,

            State::Unknown,

            &mut end_bytes_processed,

        )

        .err_tip(|| 
format!14
("{ERROR_MSG} in {resource_name}"))
?14
;

        error_if!(

            end_state != State::OptionalMetadata,

            "Expected the final state to be OptionalMetadata. Got: {end_state:?} for {resource_name} is_upload: {is_upload}"

        );

        // Slice off the processed parts of `resource_name`.

        let beginning_part = if end_bytes_processed == resource_name.len() {

            ""

        } else {

            &resource_name[..resource_name.len() - end_bytes_processed - SLASH_SIZE]

        };

        if !is_upload {

            output.instance_name = Cow::Borrowed(beginning_part);

            return Ok(output);

        }

        // If it's an upload, at this point it will have be:

        // `{?instance_name}/uploads/{uuid}`.

        // Remember, `instance_name` can contain slashes and/or special names

        // like "blobs" or "uploads".

        let mut parts = beginning_part.rsplitn(3, '/');

        output.uuid = Some(Cow::Borrowed(

            parts

                .next()

                .err_tip(|| 
format!0
("{ERROR_MSG} in {resource_name}"))
?0
,

        ));

        {

            // Sanity check that our next item is "uploads".

            let uploads = parts

                .next()

                .err_tip(|| 
format!0
("{ERROR_MSG} in {resource_name}"))
?0
;

            error_if!(

                uploads != "uploads",

                "Expected part to be 'uploads'. Got: {uploads} for {resource_name} is_upload: {is_upload}"

            );

        }

        // `instance_name` is optional.

        if let Some(
instance_name33
) = parts.next() {

            output.instance_name = Cow::Borrowed(instance_name);

        
}8

        Ok(output)

    }

    /// Returns a new `ResourceInfo` with all fields owned.

    pub fn to_owned(&self) -> ResourceInfo<'static> {

        ResourceInfo {

            instance_name: Cow::Owned(self.instance_name.to_string()),

            uuid: self.uuid.as_ref().map(|uuid| Cow::Owned(uuid.to_string())),

            compressor: self

                .compressor

                .as_ref()

                .map(|compressor| Cow::Owned(
compressor0
.
to_string0
())),

            digest_function: self

                .digest_function

                .as_ref()

                .map(|digest_function| Cow::Owned(
digest_function0
.
to_string0
())),

            hash: Cow::Owned(self.hash.to_string()),

            size: Cow::Owned(self.size.to_string()),

            expected_size: self.expected_size,

            optional_metadata: self

                .optional_metadata

                .as_ref()

                .map(|optional_metadata| Cow::Owned(
optional_metadata0
.
to_string0
())),

        }

    }

    pub fn to_string(&self, is_upload: bool) -> String {

        [

            Some(self.instance_name.as_ref()),

            is_upload.then_some("uploads"),

            self.uuid.as_ref().map(AsRef::as_ref),

            Some(

                self.compressor

                    .as_ref()

                    .map_or("blobs", |_| "compressed-blobs"),

            ),

            self.compressor.as_ref().map(AsRef::as_ref),

            self.digest_function.as_ref().map(AsRef::as_ref),

            Some(self.hash.as_ref()),

            Some(self.size.as_ref()),

            self.optional_metadata.as_ref().map(AsRef::as_ref),

        ]

        .into_iter()

        .flatten()

        .
filter35
(|part| !part.is_empty())

        .collect::<Vec<&str>>()

        .join("/")

    }

}

#[derive(Debug, PartialEq)]

enum State {

    Unknown,

    Compressor,

    DigestFunction,

    Hash,

    Size,

    OptionalMetadata,

}

// Iterate backwards looking for "(compressed-)blobs", once found, move forward

// populating the output struct. This recursive function utilises the stack to

// temporarily hold the reference to the previous item reducing the need for

// a heap allocation.

fn recursive_parse<'a>(

    rparts: &mut impl Iterator<Item = &'a str>,

    output: &mut ResourceInfo<'a>,

    mut state: State,

    bytes_processed: &mut usize,

) -> Result<State, Error> {

    let 
part280
 = rparts.next().err_tip(|| "on rparts.next()")
?8
;

    if state == State::Unknown {

        if part == "blobs" {

            *bytes_processed = part.len() + SLASH_SIZE;

            return Ok(State::DigestFunction);

        }

        if part == "compressed-blobs" {

            *bytes_processed = part.len() + SLASH_SIZE;

            return Ok(State::Compressor);

        }

        state = recursive_parse(rparts, output, state, bytes_processed)
?29
;

    }

    loop {

        match state {

            State::Unknown => {

                return Err(make_input_err!(

                    "Unknown state should never be reached in ResourceInfo::new"

                ));

            }

            State::Compressor => {

                state = State::DigestFunction;

                if COMPRESSORS.contains(&part) {

                    output.compressor = Some(Cow::Borrowed(part));

                    *bytes_processed += part.len() + SLASH_SIZE;

                    return Ok(state);

                }

                return Err(make_input_err!("Expected compressor, got {part}"));

            }

            State::DigestFunction => {

                state = State::Hash;

                if DIGEST_FUNCTIONS.contains(&part) {

                    output.digest_function = Some(Cow::Borrowed(part));

                    *bytes_processed += part.len() + SLASH_SIZE;

                    return Ok(state);

                }

            }

            State::Hash => {

                output.hash = Cow::Borrowed(part);

                *bytes_processed += part.len() + SLASH_SIZE;

                // TODO(palfrey) Set the digest_function if it is not set based on the hash size.

                return Ok(State::Size);

            }

            State::Size => {

                output.size = Cow::Borrowed(part);

                output.expected_size = part.parse::<usize>().map_err(|err| 
{3

                    Error::from_std_err(Code::InvalidArgument, &err).append(format!(

                        "Digest size_bytes was not convertible to usize. Got: {part}",

                    ))

                })?;

                *bytes_processed += part.len(); // Special case {size}, so it does not count one slash.

                return Ok(State::OptionalMetadata);

            }

            State::OptionalMetadata => {

                output.optional_metadata = Some(Cow::Borrowed(part));

                *bytes_processed += part.len() + SLASH_SIZE;

                // If we get here, we are done parsing backwards and have successfully parsed

                // everything beyond the "(compressed-)blobs" section.

                return Ok(State::OptionalMetadata);

            }

        }

    }

}