feat: add utility to convert TOML configuration file to list of environment variables (#3096)

crates/config_importer/src/cli.rs

@@ -0,0 +1,43 @@
+use std::path::PathBuf;
+
+/// Utility to import a hyperswitch TOML configuration file, convert it into environment variable
+/// key-value pairs, and export it in the specified format.
+#[derive(clap::Parser, Debug)]
+#[command(arg_required_else_help = true)]
+pub(crate) struct Args {
+    /// Input TOML configuration file.
+    #[arg(short, long, value_name = "FILE")]
+    pub(crate) input_file: PathBuf,
+
+    /// The format to convert the environment variables to.
+    #[arg(
+        value_enum,
+        short = 'f',
+        long,
+        value_name = "FORMAT",
+        default_value = "kubernetes-json"
+    )]
+    pub(crate) output_format: OutputFormat,
+
+    /// Output file. Output will be written to stdout if not specified.
+    #[arg(short, long, value_name = "FILE")]
+    pub(crate) output_file: Option<PathBuf>,
+
+    /// Prefix to be used for each environment variable in the generated output.
+    #[arg(short, long, default_value = "ROUTER")]
+    pub(crate) prefix: String,
+}
+
+/// The output format to convert environment variables to.
+#[derive(clap::ValueEnum, Clone, Copy, Debug)]
+pub(crate) enum OutputFormat {
+    /// Converts each environment variable to an object containing `name` and `value` fields.
+    ///
+    /// ```json
+    /// {
+    ///   "name": "ENVIRONMENT",
+    ///   "value": "PRODUCTION"
+    /// }
+    /// ```
+    KubernetesJson,
+}

crates/config_importer/src/main.rs

@@ -0,0 +1,98 @@
+mod cli;
+
+use std::io::{BufWriter, Write};
+
+use anyhow::Context;
+
+/// The separator used in environment variable names.
+const ENV_VAR_SEPARATOR: &str = "__";
+
+#[cfg(not(feature = "preserve_order"))]
+type EnvironmentVariableMap = std::collections::HashMap<String, String>;
+
+#[cfg(feature = "preserve_order")]
+type EnvironmentVariableMap = indexmap::IndexMap<String, String>;
+
+fn main() -> anyhow::Result<()> {
+    let args = <cli::Args as clap::Parser>::parse();
+
+    // Read input TOML file
+    let toml_contents =
+        std::fs::read_to_string(args.input_file).context("Failed to read input file")?;
+    let table = toml_contents
+        .parse::<toml::Table>()
+        .context("Failed to parse TOML file contents")?;
+
+    // Parse TOML file contents to a `HashMap` of environment variable name and value pairs
+    let env_vars = table
+        .iter()
+        .flat_map(|(key, value)| process_toml_value(&args.prefix, key, value))
+        .collect::<EnvironmentVariableMap>();
+
+    let writer: BufWriter<Box<dyn Write>> = match args.output_file {
+        // Write to file if output file is specified
+        Some(file) => BufWriter::new(Box::new(
+            std::fs::OpenOptions::new()
+                .create(true)
+                .write(true)
+                .truncate(true)
+                .open(file)
+                .context("Failed to open output file")?,
+        )),
+        // Write to stdout otherwise
+        None => BufWriter::new(Box::new(std::io::stdout().lock())),
+    };
+
+    // Write environment variables in specified format
+    match args.output_format {
+        cli::OutputFormat::KubernetesJson => {
+            let k8s_env_vars = env_vars
+                .into_iter()
+                .map(|(name, value)| KubernetesEnvironmentVariable { name, value })
+                .collect::<Vec<_>>();
+            serde_json::to_writer_pretty(writer, &k8s_env_vars)
+                .context("Failed to serialize environment variables as JSON")?
+        }
+    }
+
+    Ok(())
+}
+
+fn process_toml_value(
+    prefix: impl std::fmt::Display + Clone,
+    key: impl std::fmt::Display + Clone,
+    value: &toml::Value,
+) -> Vec<(String, String)> {
+    let key_with_prefix = format!("{prefix}{ENV_VAR_SEPARATOR}{key}").to_ascii_uppercase();
+
+    match value {
+        toml::Value::String(s) => vec![(key_with_prefix, s.to_owned())],
+        toml::Value::Integer(i) => vec![(key_with_prefix, i.to_string())],
+        toml::Value::Float(f) => vec![(key_with_prefix, f.to_string())],
+        toml::Value::Boolean(b) => vec![(key_with_prefix, b.to_string())],
+        toml::Value::Datetime(dt) => vec![(key_with_prefix, dt.to_string())],
+        toml::Value::Array(values) => {
+            if values.is_empty() {
+                return vec![(key_with_prefix, String::new())];
+            }
+
+            // This logic does not support / account for arrays of tables or arrays of arrays.
+            let (_processed_keys, processed_values) = values
+                .iter()
+                .flat_map(|v| process_toml_value(prefix.clone(), key.clone(), v))
+                .unzip::<_, _, Vec<String>, Vec<String>>();
+            vec![(key_with_prefix, processed_values.join(","))]
+        }
+        toml::Value::Table(map) => map
+            .into_iter()
+            .flat_map(|(k, v)| process_toml_value(key_with_prefix.clone(), k, v))
+            .collect(),
+    }
+}
+
+/// The Kubernetes environment variable structure containing a name and a value.
+#[derive(Debug, serde::Serialize, serde::Deserialize)]
+pub(crate) struct KubernetesEnvironmentVariable {
+    name: String,
+    value: String,
+}