1 files changed, 95 insertions, 0 deletions
diff --git a/src/ps1.rs b/src/ps1.rs
new file mode 100644
index 0000000..05b5886
--- /dev/null
+++ b/src/ps1.rs
@@ -0,0 +1,95 @@
+use std::borrow::Cow;
+use std::sync::{Arc, Mutex};
+
+use crate::parse::{ExpString, Parse};
+use crate::run::{Vars, WatchId};
+use crate::{BString, Session, bstr};
+
+pub const PROMPT_VAR: &str = "PROMPT";
+
+#[allow(unused)]
+const DEFAULT_PROMPT_VALUE_DEBUG: &bstr = b"dev [$CWD_PRETTY]# ";
+#[allow(unused)]
+const DEFAULT_PROMPT_VALUE_RELEASE: &bstr = b"[$CWD_PRETTY]# ";
+#[cfg(test)]
+const POSSIBLE_DEFAULT_PROMPT_VALUES: &[&bstr] =
+    &[DEFAULT_PROMPT_VALUE_DEBUG, DEFAULT_PROMPT_VALUE_RELEASE];
+#[cfg(debug_assertions)]
+pub const DEFAULT_PROMPT_VALUE: &bstr = DEFAULT_PROMPT_VALUE_DEBUG;
+#[cfg(not(debug_assertions))]
+pub const DEFAULT_PROMPT_VALUE: &bstr = DEFAULT_PROMPT_VALUE_RELEASE;
+
+pub struct Prompt {
+    watch_var: WatchId,
+    watch_content: Option<WatchId>,
+    parsed: Option<ExpString>,
+    cached_prompt: Option<BString>,
+}
+
+impl Prompt {
+    pub fn new(vars: &mut Vars) -> Self {
+        Self {
+            watch_var: vars.watch(vec![PROMPT_VAR.as_bytes().to_vec()]),
+            watch_content: None,
+            parsed: None,
+            cached_prompt: None,
+        }
+    }
+
+    pub fn requires_update(&self, vars: &Vars) -> bool {
+        self.parsed.iter().any(|p| p.has_commands())
+            || vars.peek_dirty(&self.watch_var)
+            || self.watch_content.iter().any(|wc| vars.peek_dirty(wc))
+    }
+
+    pub fn load_prompt(&mut self, vars: &mut Vars) {
+        if vars.pop_dirty(&self.watch_var) {
+            let prompt = vars
+                .lookup(PROMPT_VAR.as_bytes())
+                .map(Cow::into_owned)
+                .unwrap_or_else(|| DEFAULT_PROMPT_VALUE.to_vec());
+            let parsed = parse_prompt(prompt);
+            self.watch_content = Some(vars.watch(parsed.vars()));
+            self.parsed = Some(parsed);
+        }
+
+        if let Some(wc) = &self.watch_content {
+            vars.pop_dirty(wc);
+        }
+    }
+
+    pub fn eval_prompt(&mut self, se: Arc<Mutex<Session>>) {
+        let mut expander = crate::run::Executor::new(se);
+        let expanded = self
+            .parsed
+            .clone()
+            .unwrap_or_else(|| parse_prompt(DEFAULT_PROMPT_VALUE.to_vec()))
+            .expand(&mut expander)
+            .unwrap_or_else(|_| b"EXEC_ERROR$ ".to_vec());
+        self.cached_prompt = Some(expanded);
+    }
+
+    pub fn prompt(&self) -> &bstr {
+        self.cached_prompt.as_ref().map(|p| &p[..]).unwrap_or(b"> ")
+    }
+}
+
+fn parse_prompt_fallible(mut prompt: BString) -> Option<ExpString> {
+    let mut x = Vec::with_capacity(prompt.len() + 2);
+    x.push(b'"');
+    x.append(&mut prompt);
+    x.push(b'"');
+    crate::parse::ExpString::parse_from_bytes(&x).ok()
+}
+
+fn parse_prompt(prompt: BString) -> ExpString {
+    parse_prompt_fallible(prompt)
+        .unwrap_or_else(|| parse_prompt_fallible(DEFAULT_PROMPT_VALUE.to_vec()).unwrap())
+}
+
+#[test]
+fn default_prompt_should_parse() {
+    for prompt in POSSIBLE_DEFAULT_PROMPT_VALUES {
+        parse_prompt_fallible(prompt.to_vec()).unwrap();
+    }
+}