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use anyhow::{anyhow, bail, Result};
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use versions::Versioning;
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const CONJURE_MIN_VERSION: &str = "2.5.1";
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const CORRECT_FIRST_LINE: &str = "Conjure: The Automated Constraint Modelling Tool";
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/// Checks if the conjure executable is present in PATH and if it is the correct version.
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/// Returns () on success and an error on failure.
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pub fn conjure_executable() -> Result<()> {
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    let mut cmd = std::process::Command::new("conjure");
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    let output = cmd.arg("--version").output()?;
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    let stdout = String::from_utf8(output.stdout)?;
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    let stderr = String::from_utf8(output.stderr)?;
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    if !stderr.is_empty() {
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        bail!("'conjure' results in error: ".to_string() + &stderr);
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    }
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    let first = stdout
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        .lines()
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        .next()
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        .ok_or(anyhow!("Could not read stdout"))?;
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    if first != CORRECT_FIRST_LINE {
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        let path = std::env::var("PATH")?;
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        let paths = std::env::split_paths(&path);
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        let num_conjures = paths.filter(|path| path.join("conjure").exists()).count();
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        if num_conjures > 1 {
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            bail!(
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                "Conjure may be present in PATH after a conflicting name. \
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            Make sure to prepend the correct path to Conjure to PATH."
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            )
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        } else {
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            bail!("The correct Conjure executable is not present in PATH.")
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        }
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    }
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    let version_line = stdout
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        .lines()
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        .nth(1)
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        .ok_or(anyhow!("Could not read Conjure's stdout"))?;
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    let version = match version_line.strip_prefix("Release version ") {
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        Some(v) => Ok(v),
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        None => match version_line.strip_prefix("Conjure v") {
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            // New format: Conjure v2.5.1 (Repository version ...)
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            Some(v) => v.split_whitespace().next().ok_or(anyhow!(
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                "Could not read Conjure's version from: {}",
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                version_line
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            )),
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            None => Err(anyhow!(
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                "Could not read Conjure's version from: {}",
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                version_line
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            )),
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        },
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    }?;
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    if Versioning::new(version) < Versioning::new(CONJURE_MIN_VERSION) {
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        bail!(
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            "Conjure version is too old (< {}): {}",
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            CONJURE_MIN_VERSION,
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            version
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        );
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    }
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    Ok(())
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}