1 files changed, 154 insertions, 0 deletions
diff --git a/src/util.rs b/src/util.rs
new file mode 100644
index 0000000..d49d043
--- /dev/null
+++ b/src/util.rs
@@ -0,0 +1,154 @@
+use std::{path::Path, fs};
+use anyhow::{Result, Context};
+use itertools::Itertools;
+use rnix::{SyntaxKind, ast::{AttrpathValue, AttrSet, HasEntry, Entry::*}, SyntaxNode};
+use rowan::{ast::AstNode, TextSize};
+
+use crate::status_reporter::StatusReport;
+
+fn textsize_at_line(s: &str, line: usize) -> TextSize {
+    s
+        .split('\n')
+        .map(|l|
+            TextSize::of(l) + TextSize::new(1)
+        )
+        .take(line-1)
+        .sum()
+}
+
+
+fn dig_to_kind(kind: SyntaxKind, node: &SyntaxNode) -> Option<SyntaxNode> {
+    if node.kind() == kind {
+        return Some(node.clone());
+    }
+
+    node.descendants()
+        .filter(|node| node.kind() == kind)
+        .next()
+}
+
+fn add_to_meta_block(rough_pos: SyntaxNode, content: &str, main_program: &str, file: &Path, line: usize) -> Result<(String, usize)> {
+    let meta_node = dig_to_kind(SyntaxKind::NODE_ATTR_SET, &rough_pos).unwrap();
+    let meta_set = AttrSet::cast(meta_node.clone()).unwrap();
+
+    let description_entry = meta_set.entries()
+         .filter(|entry| {
+             match &entry {
+                 Inherit(it) => it.attrs().any(|c| c.to_string() == "description"),
+                 AttrpathValue(it) => it.attrpath().unwrap().to_string() == "description",
+             }
+         })
+         .exactly_one().ok()
+         .with_context(|| format!("meta node has no description attribute in {:?} at {}", file, line))?;
+    let description = description_entry.syntax();
+
+    let pos = description.text_range();
+    let indent = content[..pos.start().into()].chars().rev().position(|c| c == '\n').unwrap();
+
+    let patch = String::new()
+        + "\n"
+        + &" ".repeat(indent)
+        + "mainProgram = \"" + main_program + "\";";
+
+    Ok((patch, pos.end().into()))
+}
+
+fn edit_one(file: &Path, line: usize, main_program: &str, p: &StatusReport) -> Result<String> {
+    let mut content = fs::read_to_string(file)?;
+    let searchpos = textsize_at_line(&content, line);
+
+    p.update_item(format!("doing {:?}", file));
+    let parse = rnix::Root::parse(&content);
+    if !parse.errors().is_empty() {
+        anyhow::bail!("error: {:?}", parse.errors());
+    }
+    let tree = parse.tree();
+
+    let pos_node = tree.syntax().descendants()
+        .filter(|node| {
+            if node.kind() == SyntaxKind::NODE_ATTRPATH_VALUE {
+                let value = AttrpathValue::cast(node.clone()).unwrap();
+                node.text_range().contains(searchpos) && value.attrpath().unwrap().to_string() == "meta"
+            } else { false }
+        })
+        .exactly_one().ok();
+
+    // do we have a meta attrset already?
+    let (patch, insert_offset) = match pos_node {
+        None => {
+            let version_node = tree
+                .syntax()
+                .descendants()
+                .filter(|node| {
+                    if node.kind() == SyntaxKind::NODE_ATTRPATH_VALUE {
+                        let value = AttrpathValue::cast(node.clone()).unwrap();
+                        let name =  value.attrpath().unwrap().to_string();
+                        node.text_range().contains(searchpos + TextSize::new(5))
+                            && (name == "version" || name == "pname" || name == "name")
+                    } else { false }
+                })
+                .exactly_one().ok()
+                .with_context(|| format!("neither meta nor version node found for {:?} at {}", file, line))?;
+
+            let attrset = version_node.parent().unwrap();
+            if attrset.kind() != SyntaxKind::NODE_ATTR_SET {
+                anyhow::bail!("name not in an attrset in {:?} at {}", file, line)
+            }
+
+            // does a meta block already exist?
+            let maybe_meta_block = attrset
+                .descendants()
+                .filter(|node| {
+                    if node.kind() == SyntaxKind::NODE_ATTRPATH_VALUE {
+                        let value = AttrpathValue::cast(node.clone()).unwrap();
+                        let name =  value.attrpath().unwrap().to_string();
+                        name == "meta"
+                    } else { false }
+                })
+                .exactly_one();
+
+            if let Ok(meta) = maybe_meta_block {
+                add_to_meta_block(meta.clone(), &content, main_program, file, line)?
+            } else {
+                let before_attrset_end = Into::<usize>::into(attrset.text_range().end())
+                    - 1
+                    - content[..attrset.text_range().end().into()]
+                    .chars().rev().position(|c| c == '\n').unwrap();
+
+                let indent = content[..version_node.text_range().start().into()]
+                    .chars().rev().position(|c| c == '\n').unwrap();
+
+                // some language specific build systems don't use meta as its own attrset
+                // there's no good way to recognise these, but this seems to work fine
+                let weird_nonstandard_meta = attrset
+                    .descendants()
+                    .any(|node| {
+                        if node.kind() == SyntaxKind::NODE_ATTRPATH_VALUE {
+                            let value = AttrpathValue::cast(node.clone()).unwrap();
+                            let name =  value.attrpath().unwrap().to_string();
+                            name == "description" || name == "homepage" || name == "license"
+                        } else { false }
+                    });
+                let patch = String::new()
+                    + "\n"
+                    + &" ".repeat(indent)
+                    + if weird_nonstandard_meta { "mainProgram = \"" } else { "meta.mainProgram = \"" }
+                    + main_program + "\";";
+
+                (patch, before_attrset_end)
+            }
+        },
+        Some(pos) => {
+            add_to_meta_block(pos.clone(), &content, main_program, file, line)?
+        }
+    };
+
+
+    content = String::new()
+        + &content[..insert_offset]
+        + &patch
+        + &content[insert_offset..];
+
+    p.changed_item();
+    Ok(content)
+}