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
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148

use std::collections::HashMap;
use std::io::{Read, Seek, SeekFrom};

use bytes::Bytes;
use color_eyre::eyre::{ensure, eyre, Result};
use gcp_auth::AuthenticationManager;
use reqwest::header::{HeaderMap, HeaderValue, AUTHORIZATION, RANGE};
use reqwest::{Client, ClientBuilder};
use serde_json::Value;
use tokio::runtime::Runtime;

use crate::errors::GCSReaderError;
use crate::uri::GCSObjectURI;

macro_rules! bearer {
    ($token:expr) => {
        format!("Bearer {}", $token.as_str())
    };
}

pub enum Auth {
    Auto,
    Token(String),
}

impl Default for Auth {
    fn default() -> Self {
        Self::Auto
    }
}

impl Auth {
    async fn gcp_auth_token() -> Result<String> {
        let authentication_manager = AuthenticationManager::new().await?;
        let scopes = &["https://www.googleapis.com/auth/devstorage.read_only"];
        let token = authentication_manager.get_token(scopes).await?;
        Ok(token.as_str().to_string())
    }

    async fn token(&self) -> Result<String> {
        match self {
            Self::Auto => Self::gcp_auth_token().await,
            Self::Token(token) => Ok(token.to_string()),
        }
    }
}

#[derive(Debug)]
pub struct GCSReader {
    client: Client,
    uri: GCSObjectURI,
    pos: u64,
    len: u64,
}

impl GCSReader {
    pub fn open(uri: GCSObjectURI, auth: Auth) -> Result<Self> {
        let token = Runtime::new()?.block_on(auth.token())?;

        let md_res = reqwest::blocking::Client::new()
            .get(uri.endpoint())
            .header(AUTHORIZATION, HeaderValue::from_str(&bearer!(token))?)
            .send()?;

        ensure!(md_res.status().is_success(), GCSReaderError::from_response(md_res)?);
        let len = md_res
            .json::<HashMap<String, Value>>()?
            .get("size")
            .ok_or(GCSReaderError::GetSizeError(uri.uri()))?
            .as_str()
            .unwrap()
            .parse::<u64>()
            .unwrap();

        let mut header = HeaderMap::new();
        header.insert(AUTHORIZATION, HeaderValue::from_str(&bearer!(token))?);
        let client = ClientBuilder::new().default_headers(header).build()?;

        Ok(Self {
            client,
            uri,
            pos: 0,
            len,
        })
    }

    pub fn from_uri(uri: &str, auth: Auth) -> Result<Self> {
        let uri = GCSObjectURI::new(uri)?;
        Self::open(uri, auth)
    }

    async fn read_range(&mut self, start: u64, end: u64) -> Result<Bytes> {
        let range = format!("bytes={}-{}", start, end - 1);
        let mut header = HeaderMap::new();
        header.insert(RANGE, HeaderValue::from_str(&range)?);

        let mut params = HashMap::new();
        params.insert("alt", "media");

        let res = self
            .client
            .get(self.uri.endpoint())
            .headers(header)
            .query(&params)
            .send()
            .await?;

        ensure!(
            res.status().is_success(),
            GCSReaderError::from_async_response(res).await?
        );
        res.bytes().await.map_err(|e| eyre!(e))
    }
}

impl Read for GCSReader {
    fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
        let start = self.pos;
        let end = std::cmp::min(self.pos + (buf.len() as u64), self.len);
        if start == end {
            return Ok(0);
        }
        let bytes = Runtime::new()?
            .block_on(self.read_range(start, end))
            .map_err(|e| std::io::Error::new(std::io::ErrorKind::Other, e))?;
        let len = bytes.len() as u64;
        buf.clone_from_slice(&bytes);
        self.pos += len;
        Ok(len as usize)
    }
}

impl Seek for GCSReader {
    fn seek(&mut self, pos: SeekFrom) -> std::io::Result<u64> {
        match pos {
            SeekFrom::Start(pos) => {
                self.pos = pos;
            }
            SeekFrom::End(pos) => {
                self.pos = (self.len as i64 + pos) as u64;
            }
            SeekFrom::Current(pos) => {
                self.pos = (self.pos as i64 + pos) as u64;
            }
        }
        Ok(self.pos)
    }
}