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//! List and map builtins: construction (`list`, `map`), membership (`in`,
//! `contains_any`), lookup (`index`, `indexOrDefault`), regex line filtering
//! (`filter`, `reverseFilter`), sub-slicing (`slice`), and English list joining
//! (`englishJoin`).
use regex::Regex;
use serde_json::Value;
use std::collections::HashMap;
use tera::TeraResult;
use crate::template::engine_adapter::JsonRegisterExt;
use super::value_to_string;
pub(super) fn register(tera: &mut tera::Tera) {
// list(items=[...]) — creates a list from an items array.
// Note: the Go subexpression form `(list "a" "b")` never reaches Tera —
// the preprocessor's Pass 2 rewrites it to the array literal `["a", "b"]`.
// Pass 3 rewrites the bare call form `list "a" "b"` onto this function.
tera.register_json_function(
"list",
|args: &HashMap<String, Value>| -> TeraResult<Value> {
let items = args
.get("items")
.and_then(|v| v.as_array())
.ok_or_else(|| tera::Error::message("list requires `items` argument"))?;
Ok(Value::Array(items.clone()))
},
);
// map(pairs=[k1, v1, k2, v2, ...]) — create a map from alternating key-value pairs
// Example: {{ $m := map "a" "1" "b" "2" }}
tera.register_json_function(
"map",
|args: &HashMap<String, Value>| -> TeraResult<Value> {
let pairs = args
.get("pairs")
.and_then(|v| v.as_array())
.ok_or_else(|| tera::Error::message("map requires `pairs` argument"))?;
if pairs.len() % 2 != 0 {
return Err(tera::Error::message(
"map requires an even number of arguments (key-value pairs)",
));
}
let mut result = serde_json::Map::new();
for chunk in pairs.chunks(2) {
let key = chunk[0].as_str().unwrap_or("").to_string();
result.insert(key, chunk[1].clone());
}
Ok(Value::Object(result))
},
);
// in(items=[...], value="x") — check if a list contains a value
// Go-style: {{ in (list "a" "b" "c") "b" }} → true
// Named: {{ in(items=["a","b","c"], value="b") }} → true
// Compares all elements as strings.
let in_fn = |args: &HashMap<String, Value>| -> TeraResult<Value> {
let items = args
.get("items")
.and_then(|v| v.as_array())
.ok_or_else(|| {
tera::Error::message("in requires `items` argument (must be an array)")
})?;
let value = args
.get("value")
.ok_or_else(|| tera::Error::message("in requires `value` argument"))?;
// Convert the search value to a string for comparison.
let needle = value_to_string(value);
let found = items.iter().any(|item| value_to_string(item) == needle);
Ok(Value::Bool(found))
};
tera.register_json_function("in", in_fn);
// `contains_any` alias — avoids the Tera `in` keyword clash inside
// `{% set x = ... %}` / `{% if ... %}` bodies.
tera.register_json_function("contains_any", in_fn);
// englishJoin(items=[...], oxford=true) — join list items with commas and "and"
// Empty/whitespace-only items are filtered out before joining.
tera.register_json_function(
"englishJoin",
|args: &HashMap<String, Value>| -> TeraResult<Value> {
let items = args
.get("items")
.and_then(|v| v.as_array())
.ok_or_else(|| tera::Error::message("englishJoin requires `items` argument"))?;
let oxford = args.get("oxford").and_then(|v| v.as_bool()).unwrap_or(true);
let strs: Vec<String> = items
.iter()
.map(|v| v.as_str().unwrap_or("").to_string())
.filter(|s| !s.trim().is_empty())
.collect();
let result = match strs.len() {
0 => String::new(),
1 => strs[0].clone(),
2 => format!("{} and {}", strs[0], strs[1]),
_ => {
// Safe: match arm `_` only reachable when `strs.len() >= 3`
// per the preceding 0/1/2 cases; split_last is always Some.
let Some((last, rest)) = strs.split_last() else {
return Ok(Value::String(String::new()));
};
if oxford {
format!("{}, and {}", rest.join(", "), last)
} else {
format!("{} and {}", rest.join(", "), last)
}
}
};
Ok(Value::String(result))
},
);
// englishJoin filter: {{ (list "a" "b" "c") | englishJoin }} — pipe form
tera.register_json_filter(
"englishJoin",
|value: &Value, args: &HashMap<String, Value>| {
let items = value
.as_array()
.ok_or_else(|| tera::Error::message("englishJoin filter expects an array"))?;
let oxford = args.get("oxford").and_then(|v| v.as_bool()).unwrap_or(true);
let strs: Vec<String> = items
.iter()
.map(|v| v.as_str().unwrap_or("").to_string())
.filter(|s| !s.trim().is_empty())
.collect();
let result = match strs.len() {
0 => String::new(),
1 => strs[0].clone(),
2 => format!("{} and {}", strs[0], strs[1]),
_ => {
// Safe: match arm `_` only reachable when `strs.len() >= 3`
// per the preceding 0/1/2 cases; split_last is always Some.
let Some((last, rest)) = strs.split_last() else {
return Ok(Value::String(String::new()));
};
if oxford {
format!("{}, and {}", rest.join(", "), last)
} else {
format!("{} and {}", rest.join(", "), last)
}
}
};
Ok(Value::String(result))
},
);
// filter as pipe form: {{ items | filter(regexp="pattern") }}
tera.register_json_filter("filter", |value: &Value, args: &HashMap<String, Value>| {
let pattern = args
.get("regexp")
.and_then(|v| v.as_str())
.ok_or_else(|| tera::Error::message("filter requires `regexp` argument"))?;
let re = regex::Regex::new(pattern)
.map_err(|e| tera::Error::message(format!("invalid regex '{}': {}", pattern, e)))?;
let input = value.as_str().unwrap_or("");
let result: Vec<&str> = input.lines().filter(|line| re.is_match(line)).collect();
Ok(Value::String(result.join("\n")))
});
// reverseFilter as pipe form: {{ items | reverseFilter(regexp="pattern") }}
tera.register_json_filter(
"reverseFilter",
|value: &Value, args: &HashMap<String, Value>| {
let pattern = args
.get("regexp")
.and_then(|v| v.as_str())
.ok_or_else(|| tera::Error::message("reverseFilter requires `regexp` argument"))?;
let re = regex::Regex::new(pattern)
.map_err(|e| tera::Error::message(format!("invalid regex '{}': {}", pattern, e)))?;
let input = value.as_str().unwrap_or("");
let result: Vec<&str> = input.lines().filter(|line| !re.is_match(line)).collect();
Ok(Value::String(result.join("\n")))
},
);
// filter(items=<string|array>, regexp="pattern") — keep elements matching regex
// Accepts a multiline STRING (splits by newline, filters lines, rejoins).
// We also accept an array for convenience.
// Note: regex is compiled per call. This is acceptable for template rendering
// where each pattern is typically used once per render pass.
tera.register_json_function(
"filter",
|args: &HashMap<String, Value>| -> TeraResult<Value> {
let items_val = args
.get("items")
.ok_or_else(|| tera::Error::message("filter requires `items` argument"))?;
let pattern = args
.get("regexp")
.and_then(|v| v.as_str())
.ok_or_else(|| tera::Error::message("filter requires `regexp` argument"))?;
let re = Regex::new(pattern)
.map_err(|e| tera::Error::message(format!("filter: invalid regex: {}", e)))?;
if let Some(s) = items_val.as_str() {
// String input: split by newlines, filter matching lines, rejoin
let filtered: String = s
.lines()
.filter(|line| re.is_match(line))
.collect::<Vec<_>>()
.join("\n");
Ok(Value::String(filtered))
} else if let Some(arr) = items_val.as_array() {
// Array input: filter elements whose string value matches
let filtered: Vec<Value> = arr
.iter()
.filter(|v| v.as_str().is_some_and(|s| re.is_match(s)))
.cloned()
.collect();
Ok(Value::Array(filtered))
} else {
Err(tera::Error::message(
"filter: `items` must be a string or array",
))
}
},
);
// reverseFilter(items=<string|array>, regexp="pattern") — exclude elements matching regex
// Accepts a multiline STRING (splits by newline, filters lines, rejoins).
// We also accept an array for convenience.
// Note: regex is compiled per call. This is acceptable for template rendering
// where each pattern is typically used once per render pass.
tera.register_json_function(
"reverseFilter",
|args: &HashMap<String, Value>| -> TeraResult<Value> {
let items_val = args
.get("items")
.ok_or_else(|| tera::Error::message("reverseFilter requires `items` argument"))?;
let pattern = args
.get("regexp")
.and_then(|v| v.as_str())
.ok_or_else(|| tera::Error::message("reverseFilter requires `regexp` argument"))?;
let re = Regex::new(pattern).map_err(|e| {
tera::Error::message(format!("reverseFilter: invalid regex: {}", e))
})?;
if let Some(s) = items_val.as_str() {
// String input: split by newlines, exclude matching lines, rejoin
let filtered: String = s
.lines()
.filter(|line| !re.is_match(line))
.collect::<Vec<_>>()
.join("\n");
Ok(Value::String(filtered))
} else if let Some(arr) = items_val.as_array() {
// Array input: exclude elements whose string value matches
let filtered: Vec<Value> = arr
.iter()
.filter(|v| !v.as_str().is_some_and(|s| re.is_match(s)))
.cloned()
.collect();
Ok(Value::Array(filtered))
} else {
Err(tera::Error::message(
"reverseFilter: `items` must be a string or array",
))
}
},
);
// indexOrDefault(map={...}, key="k", default="d") — look a key up in a map,
// falling back to `default` (empty string when omitted).
tera.register_json_function(
"indexOrDefault",
|args: &HashMap<String, Value>| -> TeraResult<Value> {
let map = args
.get("map")
.and_then(|v| v.as_object())
.ok_or_else(|| tera::Error::message("indexOrDefault requires `map` argument"))?;
let key = args
.get("key")
.and_then(|v| v.as_str())
.ok_or_else(|| tera::Error::message("indexOrDefault requires `key` argument"))?;
let default = args
.get("default")
.cloned()
.unwrap_or(Value::String(String::new()));
Ok(map.get(key).cloned().unwrap_or(default))
},
);
// index(collection={...}, key="k") — access a map by key or array by index.
// Go template: {{ index .Map "key" }} → access map by key.
// Go template: {{ index .Slice 0 }} → access array by index.
// Returns empty string if key/index not found.
tera.register_json_function(
"index",
|args: &HashMap<String, Value>| -> TeraResult<Value> {
let collection = args
.get("collection")
.ok_or_else(|| tera::Error::message("index requires `collection` argument"))?;
let key = args
.get("key")
.ok_or_else(|| tera::Error::message("index requires `key` argument"))?;
match collection {
Value::Object(map) => {
let key_str = value_to_string(key);
Ok(map
.get(key_str.as_ref())
.cloned()
.unwrap_or(Value::String(String::new())))
}
Value::Array(arr) => {
if let Some(idx) = key.as_u64() {
Ok(arr
.get(idx as usize)
.cloned()
.unwrap_or(Value::String(String::new())))
} else {
Err(tera::Error::message("index: array index must be a number"))
}
}
_ => {
// For non-collection types, return empty string (graceful)
Ok(Value::String(String::new()))
}
}
},
);
// in — filter form: {{ myList | in(value="x") }}
// Checks whether the piped array contains the given value (string comparison).
let in_filter = |value: &Value, args: &HashMap<String, Value>| {
let items = value
.as_array()
.ok_or_else(|| tera::Error::message("in filter requires an array as input"))?;
let needle = args
.get("value")
.ok_or_else(|| tera::Error::message("in filter requires `value` argument"))?;
let needle_str = value_to_string(needle);
let found = items.iter().any(|item| value_to_string(item) == needle_str);
Ok(Value::Bool(found))
};
tera.register_json_filter("in", in_filter);
tera.register_json_filter("contains_any", in_filter);
// --- Go `slice` builtin (superset of Tera's native slice) ---
// Registered as a filter only, never a function: Tera's own `slice` is a
// filter, so overriding in place keeps every existing `| slice(...)` call
// working, and the Go call form `slice s 0 7` is rewritten to this filter
// by the preprocessor rather than needing a second, Go-shaped surface.
// slice(start=, end=) — substring of a string (char-boundary safe) or
// sub-slice of an array, end-exclusive (`slice s 0 7` → first 7 chars).
// `start` is OPTIONAL (default 0) and NEGATIVE indices count from the end
// (`start=-2` → last 2), matching Tera's native array slice so user
// templates relying on it keep working. Go's positional `slice X 0 7` only
// ever passes non-negative bounds, so the Go usage is a strict subset.
tera.register_json_filter("slice", |value: &Value, args: &HashMap<String, Value>| {
let start = args.get("start").and_then(|v| v.as_i64()).unwrap_or(0);
let end = args.get("end").and_then(|v| v.as_i64());
// Resolve a possibly-negative index against `len`, clamping into range.
let resolve = |idx: i64, len: i64| -> i64 {
let abs = if idx < 0 { len + idx } else { idx };
abs.clamp(0, len)
};
match value {
Value::String(s) => {
let chars: Vec<char> = s.chars().collect();
let len = chars.len() as i64;
let lo = resolve(start, len);
let hi = resolve(end.unwrap_or(len), len).max(lo) as usize;
Ok(Value::String(chars[lo as usize..hi].iter().collect()))
}
Value::Array(arr) => {
let len = arr.len() as i64;
let lo = resolve(start, len);
let hi = resolve(end.unwrap_or(len), len).max(lo) as usize;
Ok(Value::Array(arr[lo as usize..hi].to_vec()))
}
other => Err(tera::Error::message(format!(
"slice: expected a string or array, got {}",
other
))),
}
});
}