1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101

// Copyright 2024 Wladimir Palant
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// 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.

//! Byte range processing (`Range` HTTP header)

use http::header;
use crate::session_wrapper::SessionWrapper;
use crate::request_filter::RequestFilter;
use std::str::FromStr;

use crate::metadata::Metadata;

/// Represents the result of parsing the `Range` HTTP header.
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum Range {
    /// A valid range with the given start and end bounds
    Valid(u64, u64),
    /// A range that is outside of the file’s boundaries
    OutOfBounds,
}

impl Range {
    /// Parses the value of a `Range` HTTP header. The file size is required to resolve ranges
    /// specified relative to the end of file and to recognize out of bounds ranges. Ranges that
    /// cannot be parsed (unexpected format) will result in `None`.
    pub fn parse(range: &str, file_size: u64) -> Option<Self> {
        let (units, range) = range.split_once('=')?;
        if units != "bytes" {
            return None;
        }

        let (start, end) = range.trim().split_once('-')?;
        let (start, end) = if start.is_empty() {
            let len = u64::from_str(end.trim()).ok()?;
            if len > file_size {
                return Some(Self::OutOfBounds);
            }
            (file_size - len, file_size - 1)
        } else if end.is_empty() {
            (u64::from_str(start.trim()).ok()?, file_size - 1)
        } else {
            (
                u64::from_str(start.trim()).ok()?,
                u64::from_str(end.trim()).ok()?,
            )
        };

        if end >= file_size || start > end {
            Some(Self::OutOfBounds)
        } else {
            Some(Self::Valid(start, end))
        }
    }
}

/// This processes the `Range` and `If-Range` request headers to produce the requested byte range
/// if any.
///
/// `Range` header missing, using some unsupported format or overruled by `If-Range` header will
/// all result in `None` being returned.
///
/// Note: Multiple ranges are not supported.
pub fn extract_range(session: &impl SessionWrapper, meta: &Metadata) -> Option<Range> {
    let headers = &session.req_header().headers;
    if let Some(value) = headers
        .get(header::IF_RANGE)
        .and_then(|value| value.to_str().ok())
    {
        if value != meta.etag
            && !meta
                .modified
                .as_ref()
                .is_some_and(|modified| modified == value)
        {
            return None;
        }
    }

    let value = headers.get(header::RANGE)?;
    let value = value.to_str().ok()?;

    Range::parse(value, meta.size)
}

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


}