protoflow_blocks/blocks/sys/
read_env.rs

1// This is free and unencumbered software released into the public domain.
2
3extern crate std;
4
5use crate::{
6    prelude::{vec, FromStr, String},
7    StdioConfig, StdioError, StdioSystem, System,
8};
9use protoflow_core::{Block, BlockResult, BlockRuntime, InputPort, Message, OutputPort};
10use protoflow_derive::Block;
11use simple_mermaid::mermaid;
12
13/// A block that reads the value of an environment variable.
14///
15/// # Block Diagram
16#[doc = mermaid!("../../../doc/sys/read_env.mmd")]
17///
18/// # Sequence Diagram
19#[doc = mermaid!("../../../doc/sys/read_env.seq.mmd" framed)]
20///
21/// # Examples
22///
23/// ## Using the block in a system
24///
25/// ```rust
26/// # use protoflow_blocks::*;
27/// # fn main() {
28/// System::build(|s| {
29///     let name_param = s.const_string("TERM");
30///     let env_reader = s.read_env();
31///     let line_encoder = s.encode_lines();
32///     let stdout = s.write_stdout();
33///     s.connect(&name_param.output, &env_reader.name);
34///     s.connect(&env_reader.output, &line_encoder.input);
35///     s.connect(&line_encoder.output, &stdout.input);
36/// });
37/// # }
38/// ```
39///
40/// ## Running the block via the CLI
41///
42/// ```console
43/// $ protoflow execute ReadEnv name=TERM
44/// ```
45///
46#[derive(Block, Clone)]
47pub struct ReadEnv<T: Message + FromStr = String> {
48    /// The name of the environment variable to read.
49    #[input]
50    pub name: InputPort<String>,
51
52    /// The output message stream.
53    #[output]
54    pub output: OutputPort<T>,
55}
56
57impl<T: Message + FromStr> ReadEnv<T> {
58    pub fn new(name: InputPort<String>, output: OutputPort<T>) -> Self {
59        Self { name, output }
60    }
61}
62
63impl<T: Message + FromStr + 'static> ReadEnv<T> {
64    pub fn with_system(system: &System) -> Self {
65        use crate::SystemBuilding;
66        Self::new(system.input(), system.output())
67    }
68}
69
70impl<T: Message + FromStr> Block for ReadEnv<T> {
71    fn execute(&mut self, runtime: &dyn BlockRuntime) -> BlockResult {
72        runtime.wait_for(&self.name)?;
73        let name = self.name.recv()?.unwrap();
74        //self.name.close()?; // FIXME
75
76        let value = std::env::var(&name).unwrap_or_default();
77        let value = T::from_str(&value).unwrap_or_default();
78        self.output.send(&value)?;
79
80        self.output.close()?;
81        Ok(())
82    }
83}
84
85#[cfg(feature = "std")]
86impl<T: Message + FromStr> StdioSystem for ReadEnv<T> {
87    fn build_system(config: StdioConfig) -> Result<System, StdioError> {
88        use crate::{CoreBlocks, IoBlocks, SysBlocks, SystemBuilding};
89
90        config.allow_only(vec!["name"])?;
91        let name = config.get_string("name")?;
92
93        Ok(System::build(|s| {
94            let name_param = s.const_string(name);
95            let env_reader = s.read_env();
96            let line_encoder = s.encode_with(config.encoding);
97            let stdout = config.write_stdout(s);
98            s.connect(&name_param.output, &env_reader.name);
99            s.connect(&env_reader.output, &line_encoder.input);
100            s.connect(&line_encoder.output, &stdout.input);
101        }))
102    }
103}
104
105#[cfg(test)]
106mod tests {
107    use super::ReadEnv;
108    use crate::{System, SystemBuilding};
109
110    #[test]
111    fn instantiate_block() {
112        // Check that the block is constructible:
113        let _ = System::build(|s| {
114            let _ = s.block(ReadEnv::<i32>::new(s.input(), s.output()));
115        });
116    }
117}
protoflow_blocks/blocks/sys/read_env.rs

protoflow_blocks/blocks/sys/
read_env.rs
