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
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
// src/core/renderer.rs
use crate::core::expr_eval::{is_truthy, ExprEvaluator};
use crate::core::prompt_parser::TemplateNode;
use anyhow::{anyhow, Result};
use serde_json::{json, Value};
use std::collections::HashMap;
pub struct JwlRenderer {
eval: ExprEvaluator,
}
impl Default for JwlRenderer {
fn default() -> Self {
Self::new()
}
}
impl JwlRenderer {
pub fn new() -> Self {
Self {
eval: ExprEvaluator::new(),
}
}
pub fn render(&self, ast: &[TemplateNode], context: &Value) -> Result<String> {
// Flatten context object into a HashMap for scope lookup
let mut scope = HashMap::new();
if let Some(obj) = context.as_object() {
for (k, v) in obj {
scope.insert(k.clone(), v.clone());
}
}
self.render_nodes(ast, &mut scope)
}
fn render_nodes(
&self,
nodes: &[TemplateNode],
scope: &mut HashMap<String, Value>,
) -> Result<String> {
let mut output = String::new();
for node in nodes {
match node {
TemplateNode::Text(t) => output.push_str(t),
TemplateNode::Interpolation(expr) => {
let result = {
let resolver = make_resolver(scope);
self.eval
.eval(expr.trim(), &resolver)
.map_err(|e| anyhow!("Interpolation error in '{}': {}", expr, e))?
};
// Convert to display string
match &result {
Value::String(s) => output.push_str(s),
Value::Null => {} // null renders as empty
Value::Bool(b) => output.push_str(&b.to_string()),
Value::Number(n) => output.push_str(&n.to_string()),
_ => output.push_str(&serde_json::to_string(&result).unwrap_or_default()),
}
}
TemplateNode::If {
condition,
then_branch,
elif_branches,
else_branch,
} => {
let cond_res = {
let resolver = make_resolver(scope);
self.eval
.eval(condition.trim(), &resolver)
.map_err(|e| anyhow!("Condition error in '{}': {}", condition, e))?
};
if is_truthy(&cond_res) {
output.push_str(&self.render_nodes(then_branch, scope)?);
} else {
let mut matched = false;
for (elif_cond, elif_body) in elif_branches {
let elif_res = {
let elif_resolver = make_resolver(scope);
self.eval
.eval(elif_cond.trim(), &elif_resolver)
.map_err(|e| {
anyhow!("Elif condition error in '{}': {}", elif_cond, e)
})?
};
if is_truthy(&elif_res) {
output.push_str(&self.render_nodes(elif_body, scope)?);
matched = true;
break;
}
}
if !matched {
if let Some(eb) = else_branch {
output.push_str(&self.render_nodes(eb, scope)?);
}
}
}
}
TemplateNode::For {
var_name,
iterable_expr,
body,
else_branch,
} => {
let list = {
let resolver = make_resolver(scope);
self.eval
.eval(iterable_expr.trim(), &resolver)
.map_err(|e| anyhow!("For loop error in '{}': {}", iterable_expr, e))?
};
let mut ran_loop = false;
if let Value::Array(array) = list {
let total = array.len();
if total > 0 {
ran_loop = true;
for (idx, item) in array.into_iter().enumerate() {
// Inject loop variable and loop metadata into scope
scope.insert(var_name.clone(), item);
scope.insert(
"loop".to_string(),
json!({
"index0": idx,
"index": idx + 1,
"first": idx == 0,
"last": idx == total - 1,
}),
);
output.push_str(&self.render_nodes(body, scope)?);
// Clean up loop variables
scope.remove(var_name);
scope.remove("loop");
}
}
}
if !ran_loop {
if let Some(eb) = else_branch {
output.push_str(&self.render_nodes(eb, scope)?);
}
}
}
TemplateNode::Tag {
children,
self_closing,
..
} => {
// Tags are transparent containers in prompt rendering mode.
// Block tags render their children; self-closing tags produce no output.
if !self_closing {
output.push_str(&self.render_nodes(children, scope)?);
}
}
}
}
Ok(output)
}
}
/// Create a resolver from a scope HashMap.
/// The resolver looks up bare identifiers directly in scope,
/// and handles dot-path access into nested values.
fn make_resolver<'a>(scope: &'a HashMap<String, Value>) -> impl Fn(&str) -> Option<Value> + 'a {
move |path: &str| {
let parts: Vec<&str> = path.split('.').collect();
if parts.is_empty() {
return None;
}
// Look up the root variable in scope
let root = scope.get(parts[0])?;
// Navigate into nested fields
let mut current = root.clone();
for part in &parts[1..] {
current = match current {
Value::Object(ref map) => map.get(*part)?.clone(),
_ => return None,
};
}
Some(current)
}
}