feat: expr

Cargo.toml

@@ -10,7 +10,7 @@ members = [
     "fastn-lang",
     "foo",
     "fastn-ds", 
-    "fastn-update",
+    "fastn-update", "fastn-expr",
     # "fastn-wasm",
     # "fastn-runtime",
 ]
@@ -93,6 +93,7 @@ fastn-package = { path = "fastn-package" }
 fastn-runtime = { path = "fastn-runtime" }
 fastn-wasm = { path = "fastn-wasm" }
 fastn-grammar = { path = "fastn-grammar" }
+fastn-expr = { path = "fastn-expr" }
 fluent = "0.16"
 format_num = "0.1"
 ftd = { path = "ftd" }

fastn-core/Cargo.toml

@@ -86,6 +86,7 @@ uuid.workspace = true
 validator.workspace = true
 zxcvbn.workspace = true
 zip.workspace = true
+fastn-expr.workspace = true
 
 [dev-dependencies]
 fbt-lib.workspace = true

fastn-core/src/error.rs

@@ -18,6 +18,9 @@ pub enum Error {
     #[error("FTDP1Error: {}", _0)]
     FTDP1Error(#[from] ftd::p1::Error),
 
+    #[error("FTDInterpolationError: {}", _0)]
+    FTDInterpolationError(#[from] fastn_expr::interpolator::InterpolationError),
+
     #[error("FTDAstError: {}", _0)]
     FTDAstError(#[from] ftd::ast::Error),
 

fastn-core/src/utils.rs

@@ -1091,21 +1091,12 @@ pub(crate) async fn interpolate_env_vars(
 
         let key = captures.get(1).unwrap().as_str().trim();
 
-        let value = match key {
-            key if key.starts_with("env.") => {
-                let env_key = key.trim_start_matches("env.");
-                ds.env(env_key).await.map_err(|e| {
-                    fastn_core::error::Error::generic(format!(
-                        "Failed to interpolate environment variable '{}' in endpoint.: {e}",
-                        env_key
-                    ))
-                })?
-            }
-            _ => {
-                return Err(fastn_core::error::Error::generic(format!(
-                    "Failed to interpolate unknown variable '{}' in endpoint.",
-                    key
-                )))
+        let value = match get_interpolated_value(ds, key).await {
+            Ok(value) => value,
+            Err(e) => {
+                return fastn_core::generic_error(format!(
+                    "Failed to interpolate value in endpoint: {e}"
+                ));
             }
         };
 
@@ -1117,3 +1108,52 @@ pub(crate) async fn interpolate_env_vars(
     result.push_str(&endpoint[last_end..]);
     Ok(result)
 }
+
+async fn get_interpolated_value(
+    ds: &fastn_ds::DocumentStore,
+    input: &str,
+) -> fastn_core::Result<String> {
+    let value = match fastn_expr::interpolator::get_var_name_and_default(input)? {
+        (Some(var_name), default_value) => match var_name {
+            key if key.starts_with("env.") => {
+                let env_key = key.trim_start_matches("env.");
+
+                get_env_value_or_default(ds, env_key, default_value).await?
+            }
+            _ => {
+                return Err(fastn_core::error::Error::generic(format!(
+                    "unknown variable '{}'.",
+                    input,
+                )))
+            }
+        },
+        (None, Some(default_value)) => default_value,
+        _ => {
+            return Err(fastn_core::error::Error::generic(
+                "unsupported interpolation syntax used.".to_string(),
+            ))
+        }
+    };
+
+    Ok(value)
+}
+
+async fn get_env_value_or_default(
+    ds: &fastn_ds::DocumentStore,
+    env_key: &str,
+    default_value: Option<String>,
+) -> fastn_core::Result<String> {
+    match ds.env(env_key).await {
+        Ok(value) => Ok(value),
+        Err(e) => {
+            if let Some(default_value) = default_value {
+                Ok(default_value)
+            } else {
+                Err(fastn_core::error::Error::generic(format!(
+                    "could not find environment variable '{}': {e}",
+                    env_key
+                )))
+            }
+        }
+    }
+}

fastn-core/tests/21-http-endpoint/cmd.p1

@@ -7,4 +7,5 @@ output: .build
 Updated package dependency.
 Processing fastn-stack.github.io/http-endpoint-test/manifest.json ... done in <omitted>
 Processing fastn-stack.github.io/http-endpoint-test/FASTN/ ... done in <omitted>
-Processing fastn-stack.github.io/http-endpoint-test/ ... done in <omitted>
+Processing fastn-stack.github.io/http-endpoint-test/ ... calling `http` processor with url: http://reqres.in/api/users/2
+done in <omitted>

fastn-core/tests/21-http-endpoint/input/FASTN.ftd

@@ -5,3 +5,4 @@
 -- fastn.url-mappings:
 
 /api/* -> http+proxy://${env.REQRES}/api/*
+/api/v2/* -> http+proxy://${env.EXAMPLE or "example.com"}/api/v2/*

fastn-core/tests/21-http-endpoint/input/index.ftd

@@ -14,8 +14,13 @@ $processor$: pr.http
 url: /api/users/2
 
 
+
+-- display-user: $u
+
+
+
 -- component display-user:
-user u:
+caption user u:
 
 -- ftd.row:
 spacing.fixed.rem: 1

fastn-core/tests/21-http-endpoint/output/FASTN.ftd

@@ -5,3 +5,4 @@
 -- fastn.url-mappings:
 
 /api/* -> http+proxy://${env.REQRES}/api/*
+/api/v2/* -> http+proxy://${env.EXAMPLE or "example.com"}/api/v2/*

fastn-core/tests/21-http-endpoint/output/index.ftd

@@ -14,8 +14,13 @@ $processor$: pr.http
 url: /api/users/2
 
 
+
+-- display-user: $u
+
+
+
 -- component display-user:
-user u:
+caption user u:
 
 -- ftd.row:
 spacing.fixed.rem: 1

fastn-core/tests/21-http-endpoint/output/manifest.json

@@ -2,15 +2,15 @@
   "files": {
     "FASTN.ftd": {
       "name": "FASTN.ftd",
-      "checksum": "1A051A65F8DEDF8464FC2B0BC057E78D565655893F0435EE5E145EB23A667C7C",
-      "size": 145
+      "checksum": "ABE2D16D99185C27D6D576949BDC5B0E5DD95C64731873126B1033A9C0E8B4DB",
+      "size": 212
     },
     "index.ftd": {
       "name": "index.ftd",
-      "checksum": "6010AAF5DE489BB2FDA2A46ADC560309F2C5E4A5D16E5CCC2787D6B4C60D8AE5",
-      "size": 424
+      "checksum": "C0F81A62DC5A838C286CDFE72FFD50467C99312D3A1367AFC14105941AB12BC9",
+      "size": 456
     }
   },
   "zip_url": "https://codeload.github.com/fastn-stack/http-endpoint-test/zip/refs/heads/main",
-  "checksum": "6B712EBA21408F2619EC7EBB3B90BAE0879A4AA451F08BD9FA54F2D34159BBE0"
+  "checksum": "D365DD22B14D7FFB1C3D6E27AF6FD658351AB6B3F4A2ABA2E55BC63DC61898FC"
 }

fastn-expr/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "fastn-expr"
+version = "0.1.0"
+authors.workspace = true
+edition.workspace = true
+description.workspace = true
+license.workspace = true
+repository.workspace = true
+homepage.workspace = true
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+thiserror.workspace = true

fastn-expr/src/interpolator.rs

@@ -0,0 +1,47 @@
+#[derive(thiserror::Error, Debug)]
+pub enum InterpolationError {
+    #[error("Failed to parse interpolation: {0}")]
+    FailedToParse(#[from] fastn_expr::parser::ParseError),
+    #[error("Failed to interpolate: {0}")]
+    CantInterpolate(String),
+}
+
+pub fn get_var_name_and_default(
+    key: &str,
+) -> Result<(Option<String>, Option<String>), InterpolationError> {
+    let result = fastn_expr::parser::parse(key)?;
+
+    match result {
+        fastn_expr::parser::ExprNode::Binary(
+            boxed_lhs,
+            fastn_expr::tokenizer::Operator::Or,
+            boxed_rhs,
+        ) => {
+            let (var_name, default_value) = match (*boxed_lhs, *boxed_rhs) {
+                (
+                    fastn_expr::parser::ExprNode::Identifier(var_name),
+                    fastn_expr::parser::ExprNode::StringLiteral(default_value),
+                ) => (Some(var_name.clone()), Some(default_value)),
+                (
+                    fastn_expr::parser::ExprNode::Identifier(var_name),
+                    fastn_expr::parser::ExprNode::Integer(default_value),
+                ) => (Some(var_name.clone()), Some(default_value.to_string())),
+                (
+                    fastn_expr::parser::ExprNode::Identifier(var_name),
+                    fastn_expr::parser::ExprNode::Decimal(default_value),
+                ) => (Some(var_name.clone()), Some(default_value.to_string())),
+                _ => {
+                    return Err(InterpolationError::CantInterpolate(
+                        "Invalid expression".to_string(),
+                    ))
+                }
+            };
+
+            Ok((var_name, default_value))
+        }
+        fastn_expr::parser::ExprNode::Identifier(var_name) => Ok((Some(var_name), None)),
+        fastn_expr::parser::ExprNode::StringLiteral(value) => Ok((None, Some(value))),
+        fastn_expr::parser::ExprNode::Integer(value) => Ok((None, Some(value.to_string()))),
+        fastn_expr::parser::ExprNode::Decimal(value) => Ok((None, Some(value.to_string()))),
+    }
+}

fastn-expr/src/lib.rs

@@ -0,0 +1,5 @@
+pub extern crate self as fastn_expr;
+
+pub mod interpolator;
+pub(crate) mod parser;
+pub(crate) mod tokenizer;