azure_storage_blob 0.10.0

// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License.

use azure_core::error::{Error, ErrorKind, ResultExt};
use azure_core::http::headers::{Header, HeaderName};
use std::fmt;
use std::ops::{Range, RangeFrom};
use std::str::FromStr;

const PREFIX: &str = "bytes ";
const WILDCARD: &str = "*";
const CONTENT_RANGE_ID: HeaderName = HeaderName::from_static("content-range");

type Result<T> = azure_core::Result<T>;

/// Trait to convert a value into an HTTP Range header.
/// Implemented on `Range<>` and `RangeFrom<>`.
/// Note that `Range<>` uses an exclusive end value while
/// HTTP uses an inclusive end value.
pub(crate) trait IntoRangeHeader {
    fn as_range_header(&self) -> String;
}

impl IntoRangeHeader for Range<usize> {
    fn as_range_header(&self) -> String {
        format!("bytes={}-{}", self.start, self.end - 1)
    }
}

impl IntoRangeHeader for RangeFrom<usize> {
    fn as_range_header(&self) -> String {
        format!("bytes={}-", self.start)
    }
}

/// Represents the `Content-Range` HTTP response header.
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub(crate) struct ContentRange {
    /// Inclusive start and exclusive end of the range.
    pub range: Option<(usize, usize)>,
    /// Total length of the remote resource.
    pub total_len: Option<usize>,
}

impl Header for ContentRange {
    fn name(&self) -> azure_core::http::headers::HeaderName {
        CONTENT_RANGE_ID
    }

    fn value(&self) -> azure_core::http::headers::HeaderValue {
        let range_str = match self.range {
            Some(range) => format!("{}-{}", range.0, range.1),
            None => WILDCARD.to_string(),
        };
        let len_str = match self.total_len {
            Some(len) => len.to_string(),
            None => WILDCARD.to_string(),
        };
        format!("{}{}/{}", PREFIX, range_str, len_str).into()
    }
}

impl FromStr for ContentRange {
    type Err = Error;
    fn from_str(s: &str) -> Result<ContentRange> {
        let remaining = s.strip_prefix(PREFIX).ok_or_else(|| {
            Error::with_message_fn(ErrorKind::Other, || {
                format!(
                    "expected token \"{PREFIX}\" not found when parsing ContentRange from \"{s}\""
                )
            })
        })?;

        let mut split_at_slash = remaining.split('/');

        let range = parse_range(split_at_slash.next().ok_or_else(|| {
            Error::with_message(ErrorKind::Other, "Unexpected end of Content-Range.")
        })?)?;

        let total_len = parse_total_length(split_at_slash.next().ok_or_else(|| {
            Error::with_message_fn(ErrorKind::Other, || {
                format!(
                    "expected token \"{}\" not found when parsing ContentRange from \"{}\"",
                    "/", s
                )
            })
        })?)?;

        Ok(ContentRange { range, total_len })
    }
}

/// Parses the range portion of the Content-Range header: `<unit> <range>/<size>`.
/// The range portion can be of the format `<start>-<end>` or a wildcard `*`.
/// `start` and `end` are both serialized as inclusive values, but we return a
/// half-open range (inclusive start, exclusive end).
fn parse_range(s: &str) -> Result<Option<(usize, usize)>> {
    let s = s.trim();
    if s == WILDCARD {
        return Ok(None);
    }

    let mut split_at_dash = s.split('-');
    let start = split_at_dash
        .next()
        .ok_or_else(|| Error::with_message(ErrorKind::Other, "Unexpected end of Content-Range."))?
        .parse::<usize>()
        .with_kind(ErrorKind::DataConversion)?;
    let end = split_at_dash
        .next()
        .ok_or_else(|| {
            Error::with_message_fn(ErrorKind::Other, || {
                format!(
                    "expected token \"{}\" not found when parsing ContentRange from \"{}\"",
                    "-", s
                )
            })
        })?
        .parse::<usize>()
        .with_kind(ErrorKind::DataConversion)?;

    Ok(Some((start, end + 1)))
}

fn parse_total_length(s: &str) -> Result<Option<usize>> {
    let s = s.trim();
    if s == WILDCARD {
        return Ok(None);
    }
    Ok(Some(s.parse().with_kind(ErrorKind::DataConversion)?))
}

impl fmt::Display for ContentRange {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(
            f,
            "{}{}/{}",
            PREFIX,
            self.range
                .map(|range| format!("{}-{}", range.0, range.1 - 1))
                .unwrap_or(WILDCARD.into()),
            self.total_len
                .map(|len| len.to_string())
                .unwrap_or(WILDCARD.into()),
        )
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn parse() {
        let range = "bytes 172032-172489/172490"
            .parse::<ContentRange>()
            .unwrap();

        assert_eq!(range.range.unwrap().0, 172032);
        assert_eq!(range.range.unwrap().1, 172490);
        assert_eq!(range.total_len.unwrap(), 172490);
    }

    #[test]
    fn parse_no_starting_token() {
        "something else".parse::<ContentRange>().unwrap_err();
    }

    #[test]
    fn parse_no_dash() {
        "bytes 100".parse::<ContentRange>().unwrap_err();
    }

    #[test]
    fn parse_no_slash() {
        "bytes 100-500".parse::<ContentRange>().unwrap_err();
    }

    #[test]
    fn display() {
        let range = ContentRange {
            range: Some((100, 500)),
            total_len: Some(5000),
        };

        let txt = format!("{range}");

        assert_eq!(txt, "bytes 100-499/5000");
    }
}