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//! Key-based comparison of two literal-document interpretations.
//!
//! Comparison is independent of source order and formatting. It uses each
//! document's effective lookup entry, so duplicate-key policy and bare-key
//! participation are honored. No expansion, environment access or I/O occurs.
use alloc::{
collections::BTreeSet,
string::{String, ToString},
vec::Vec,
};
use crate::{AssignmentState, Document};
/// The effective value side of one compared key.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct ComparedValue {
/// Whether the declaration is bare, empty or assigned a non-empty value.
pub state: AssignmentState,
/// Decoded literal value; `None` for a bare declaration.
pub value: Option<String>,
/// Whether the declaration carries an `export` prefix.
pub exported: bool,
}
/// Why a key appears in a [`Comparison`].
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
#[non_exhaustive]
pub enum DifferenceKind {
/// The key has no effective declaration in the right document.
OnlyLeft,
/// The key has no effective declaration in the left document.
OnlyRight,
/// Both sides declare the key, but bare/empty/value states differ.
State,
/// Both sides have the same state but different decoded values.
Value,
/// The decoded value is the same but export participation differs.
Export,
}
/// One changed key and its effective values on both sides.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct ComparisonEntry {
/// The declaration key.
pub key: String,
/// The effective left declaration, or `None` when absent.
pub left: Option<ComparedValue>,
/// The effective right declaration, or `None` when absent.
pub right: Option<ComparedValue>,
/// The primary difference category.
pub kind: DifferenceKind,
}
/// Changed keys between two documents in stable key order.
///
/// Keys present on the left appear in left source order, followed by keys that
/// occur only on the right in right source order. Keys with identical effective
/// values are omitted.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Comparison {
differences: Vec<ComparisonEntry>,
}
impl Comparison {
/// Changed entries in stable key order.
#[must_use]
pub fn differences(&self) -> &[ComparisonEntry] {
&self.differences
}
/// Whether the effective declarations are identical.
#[must_use]
pub fn is_empty(&self) -> bool {
self.differences.is_empty()
}
/// Number of changed keys.
#[must_use]
pub fn len(&self) -> usize {
self.differences.len()
}
}
impl Document<'_> {
/// Compare effective declarations by key.
///
/// Each side contributes only declarations that participate in lookup.
/// Duplicate resolution uses the document's own `Duplicates` policy. A
/// bare declaration, an assigned empty value and an absent key are distinct
/// states; decoded values are compared literally. Export differences are
/// reported only when state and value are otherwise equal.
///
/// # Examples
///
/// ```
/// use adotenv::{parse_strict, DifferenceKind};
///
/// let left = parse_strict("A=1\nB=\nC=3\n").unwrap();
/// let right = parse_strict("A=2\nB\nD=4\n").unwrap();
/// let comparison = left.compare(&right);
/// let kinds: Vec<_> = comparison
/// .differences()
/// .iter()
/// .map(|entry| (entry.key.as_str(), entry.kind))
/// .collect();
/// assert_eq!(
/// kinds,
/// [
/// ("A", DifferenceKind::Value),
/// ("B", DifferenceKind::State),
/// ("C", DifferenceKind::OnlyLeft),
/// ("D", DifferenceKind::OnlyRight),
/// ]
/// );
/// ```
#[must_use]
pub fn compare<'a>(&'a self, other: &'a Document<'_>) -> Comparison {
let mut keys = Vec::new();
let mut seen = BTreeSet::new();
collect_keys(self, &mut keys, &mut seen);
collect_keys(other, &mut keys, &mut seen);
let mut differences = Vec::new();
for key in keys {
let left = self.get_entry(&key).map(snapshot);
let right = other.get_entry(&key).map(snapshot);
let kind = match (&left, &right) {
(None, Some(_)) => DifferenceKind::OnlyRight,
(Some(_), None) => DifferenceKind::OnlyLeft,
(Some(left), Some(right)) if left.state != right.state => DifferenceKind::State,
(Some(left), Some(right)) if left.value != right.value => DifferenceKind::Value,
(Some(left), Some(right)) if left.exported != right.exported => {
DifferenceKind::Export
}
(Some(_), Some(_)) | (None, None) => continue,
};
differences.push(ComparisonEntry {
key,
left,
right,
kind,
});
}
Comparison { differences }
}
}
fn collect_keys(document: &Document<'_>, keys: &mut Vec<String>, seen: &mut BTreeSet<String>) {
for entry in document.entries() {
if !entry.participates_in_lookup() {
continue;
}
let key = entry.key();
if !seen.contains(key) {
seen.insert(key.to_string());
keys.push(key.to_string());
}
}
}
fn snapshot(entry: crate::Entry<'_>) -> ComparedValue {
ComparedValue {
state: entry.state(),
value: entry.value().map(ToString::to_string),
exported: entry.exported(),
}
}