nuwiki/crates/nuwiki-lsp/src/commands.rs

//! `workspace/executeCommand` dispatcher.
//!
//! Phase 13 introduced the router + `nuwiki.file.delete`. Phase 14 adds
//! the cheap surgical edits — checkbox toggle/cycle/reject, heading
//! promote/demote, "next task" navigation — that account for the bulk
//! of vimwiki users' daily keymap traffic. Heavier commands (table
//! reflow, list renumber, link normalisation, colorize) are scoped for
//! a follow-up since each needs its own structural rewriter.
//!
//! Every command resolves to either a `WorkspaceEdit` (the server then
//! calls `apply_edit`) or a JSON `Value` (returned to the client) — see
//! `CommandOutcome` below. `ops::*` are the pure functions the dispatcher
//! wraps; they're `pub` so tests and future tooling can drive them
//! without spinning up a Backend.

use serde::Deserialize;
use serde_json::Value;
use std::sync::atomic::Ordering;
use tower_lsp::lsp_types::{Position as LspPosition, Url, WorkspaceEdit};

use crate::edits::{op_delete, WorkspaceEditBuilder};
use crate::nav;
use crate::Backend;

/// Result of a single executeCommand dispatch.
pub enum CommandOutcome {
    /// Push to the client via `workspace/applyEdit`.
    Edit(WorkspaceEdit),
    /// Return verbatim as the executeCommand response.
    Value(Value),
}

/// All commands the server advertises in `ExecuteCommandOptions.commands`.
/// Keep in lock-step with the match arms in `execute`.
pub const COMMANDS: &[&str] = &[
    "nuwiki.file.delete",
    "nuwiki.list.toggleCheckbox",
    "nuwiki.list.cycleCheckbox",
    "nuwiki.list.rejectCheckbox",
    "nuwiki.list.nextTask",
    "nuwiki.heading.addLevel",
    "nuwiki.heading.removeLevel",
];

pub(crate) async fn execute(
    backend: &Backend,
    command: &str,
    args: Vec<Value>,
) -> Result<Option<CommandOutcome>, String> {
    match command {
        "nuwiki.file.delete" => file_delete(args).map(|opt| opt.map(CommandOutcome::Edit)),
        "nuwiki.list.toggleCheckbox" => {
            Ok(list_checkbox(backend, args, ops::toggle_state)?.map(CommandOutcome::Edit))
        }
        "nuwiki.list.cycleCheckbox" => {
            Ok(list_checkbox(backend, args, ops::cycle_state)?.map(CommandOutcome::Edit))
        }
        "nuwiki.list.rejectCheckbox" => {
            Ok(list_checkbox(backend, args, ops::reject_state)?.map(CommandOutcome::Edit))
        }
        "nuwiki.list.nextTask" => {
            list_next_task(backend, args).map(|opt| opt.map(CommandOutcome::Value))
        }
        "nuwiki.heading.addLevel" => {
            Ok(heading_change_level(backend, args, 1)?.map(CommandOutcome::Edit))
        }
        "nuwiki.heading.removeLevel" => {
            Ok(heading_change_level(backend, args, -1)?.map(CommandOutcome::Edit))
        }
        other => Err(format!("unknown nuwiki command: {other}")),
    }
}

#[derive(Deserialize)]
struct PosArgs {
    uri: Url,
    position: LspPosition,
}

fn parse_pos(args: Vec<Value>) -> Result<PosArgs, String> {
    let raw = args
        .into_iter()
        .next()
        .ok_or_else(|| "missing { uri, position } argument".to_string())?;
    serde_json::from_value(raw).map_err(|e| format!("invalid args: {e}"))
}

fn file_delete(args: Vec<Value>) -> Result<Option<WorkspaceEdit>, String> {
    #[derive(Deserialize)]
    struct Args {
        uri: Url,
    }
    let raw = args
        .into_iter()
        .next()
        .ok_or_else(|| "nuwiki.file.delete: missing arguments".to_string())?;
    let parsed: Args = serde_json::from_value(raw)
        .map_err(|e| format!("nuwiki.file.delete: invalid args — {e}"))?;
    let mut builder = WorkspaceEditBuilder::new();
    builder.file_op(op_delete(parsed.uri));
    Ok(Some(builder.build()))
}

fn list_checkbox(
    backend: &Backend,
    args: Vec<Value>,
    mutate: fn(&str) -> Option<&'static str>,
) -> Result<Option<WorkspaceEdit>, String> {
    let p = parse_pos(args)?;
    let doc = match backend.documents.get(&p.uri) {
        Some(d) => d,
        None => return Ok(None),
    };
    let utf8 = backend.use_utf8.load(Ordering::Relaxed);
    let (line, col) = nav::lsp_to_byte_pos(p.position, &doc.text, utf8);
    Ok(ops::checkbox_edit(
        &doc.text, &doc.ast, &p.uri, line, col, utf8, mutate,
    ))
}

fn list_next_task(backend: &Backend, args: Vec<Value>) -> Result<Option<Value>, String> {
    let p = parse_pos(args)?;
    let doc = match backend.documents.get(&p.uri) {
        Some(d) => d,
        None => return Ok(None),
    };
    let utf8 = backend.use_utf8.load(Ordering::Relaxed);
    let (line, col) = nav::lsp_to_byte_pos(p.position, &doc.text, utf8);
    let Some(loc) = ops::next_task(&doc.ast, &p.uri, &doc.text, line, col, utf8) else {
        return Ok(None);
    };
    serde_json::to_value(loc)
        .map(Some)
        .map_err(|e| format!("nuwiki.list.nextTask: serialization failed — {e}"))
}

fn heading_change_level(
    backend: &Backend,
    args: Vec<Value>,
    delta: i32,
) -> Result<Option<WorkspaceEdit>, String> {
    let p = parse_pos(args)?;
    let doc = match backend.documents.get(&p.uri) {
        Some(d) => d,
        None => return Ok(None),
    };
    let utf8 = backend.use_utf8.load(Ordering::Relaxed);
    let (line, col) = nav::lsp_to_byte_pos(p.position, &doc.text, utf8);
    Ok(ops::heading_change_level(
        &doc.text, &doc.ast, &p.uri, line, col, utf8, delta,
    ))
}

// ===== Pure operations =====

pub mod ops {
    use super::*;
    use crate::edits::text_edit_replace;
    use nuwiki_core::ast::{
        BlockNode, BlockquoteNode, CheckboxState, DocumentNode, HeadingNode, ListItemNode,
        ListNode, Span,
    };
    use tower_lsp::lsp_types::Location;

    /// Toggle ` ↔ X. Mid-states (`.`, `o`, `O`) snap forward to `X`.
    /// Rejected (`-`) reverts to empty.
    pub fn toggle_state(current: &str) -> Option<&'static str> {
        match current {
            "[ ]" => Some("[X]"),
            "[X]" => Some("[ ]"),
            "[.]" | "[o]" | "[O]" => Some("[X]"),
            "[-]" => Some("[ ]"),
            _ => None,
        }
    }

    /// `[ ]` → `[.]` → `[o]` → `[O]` → `[X]` → `[ ]`. `[-]` → `[ ]`.
    pub fn cycle_state(current: &str) -> Option<&'static str> {
        match current {
            "[ ]" => Some("[.]"),
            "[.]" => Some("[o]"),
            "[o]" => Some("[O]"),
            "[O]" => Some("[X]"),
            "[X]" => Some("[ ]"),
            "[-]" => Some("[ ]"),
            _ => None,
        }
    }

    /// Toggle the `[-]` "rejected" state.
    pub fn reject_state(current: &str) -> Option<&'static str> {
        match current {
            "[-]" => Some("[ ]"),
            _ => Some("[-]"),
        }
    }

    pub fn checkbox_edit(
        text: &str,
        ast: &DocumentNode,
        uri: &Url,
        line: u32,
        col: u32,
        utf8: bool,
        mutate: fn(&str) -> Option<&'static str>,
    ) -> Option<WorkspaceEdit> {
        let item = find_list_item_at(ast, line, col)?;
        let cb_span = find_checkbox_span(text, item.span)?;
        let cur = &text[cb_span.start.offset..cb_span.end.offset];
        let new = mutate(cur)?;
        let mut b = WorkspaceEditBuilder::new();
        b.edit(
            uri.clone(),
            text_edit_replace(cb_span, new.to_string(), text, utf8),
        );
        Some(b.build())
    }

    pub fn next_task(
        ast: &DocumentNode,
        uri: &Url,
        text: &str,
        line: u32,
        _col: u32,
        utf8: bool,
    ) -> Option<Location> {
        // Walk in source order; first task at line > cursor wins. Wraps to
        // the start of the document if nothing found after cursor — matches
        // vimwiki's `gnt`.
        let mut items: Vec<&ListItemNode> = Vec::new();
        for block in &ast.children {
            collect_list_items(block, &mut items);
        }
        let is_unfinished = |it: &&ListItemNode| match it.checkbox {
            Some(CheckboxState::Done) | Some(CheckboxState::Rejected) => false,
            Some(_) | None => it.checkbox.is_some(),
        };
        let after = items
            .iter()
            .find(|it| it.span.start.line > line && is_unfinished(it));
        let chosen = after.or_else(|| items.iter().find(|it| is_unfinished(it)))?;
        let span = chosen.span;
        Some(Location {
            uri: uri.clone(),
            range: crate::edits::text_edit_replace(span, String::new(), text, utf8).range,
        })
    }

    fn collect_list_items<'a>(block: &'a BlockNode, out: &mut Vec<&'a ListItemNode>) {
        match block {
            BlockNode::List(ListNode { items, .. }) => {
                for it in items {
                    out.push(it);
                    if let Some(sub) = &it.sublist {
                        for sub_it in &sub.items {
                            collect_list_items_from_item(sub_it, out);
                        }
                    }
                }
            }
            BlockNode::Blockquote(BlockquoteNode { children, .. }) => {
                for c in children {
                    collect_list_items(c, out);
                }
            }
            _ => {}
        }
    }

    fn collect_list_items_from_item<'a>(item: &'a ListItemNode, out: &mut Vec<&'a ListItemNode>) {
        out.push(item);
        if let Some(sub) = &item.sublist {
            for sub_it in &sub.items {
                collect_list_items_from_item(sub_it, out);
            }
        }
    }

    pub fn heading_change_level(
        text: &str,
        ast: &DocumentNode,
        uri: &Url,
        line: u32,
        _col: u32,
        utf8: bool,
        delta: i32,
    ) -> Option<WorkspaceEdit> {
        let heading = find_heading_at(ast, line)?;
        let current = heading.level as i32;
        let new_level = (current + delta).clamp(1, 6) as u8;
        if new_level == heading.level {
            return None;
        }
        let new_text = rewrite_heading_with_level(text, heading.span, new_level)?;
        let mut b = WorkspaceEditBuilder::new();
        b.edit(
            uri.clone(),
            text_edit_replace(heading.span, new_text, text, utf8),
        );
        Some(b.build())
    }

    fn find_heading_at(ast: &DocumentNode, line: u32) -> Option<&HeadingNode> {
        for block in &ast.children {
            if let BlockNode::Heading(h) = block {
                if h.span.start.line == line {
                    return Some(h);
                }
            }
        }
        None
    }

    /// Rewrite a heading's source so it has `new_level` `=`s on each side.
    /// Returns `None` if the source doesn't have a balanced `=` ... `=`
    /// shape (defensive — the lexer should guarantee this, but we don't
    /// crash if the buffer was edited mid-flight).
    pub fn rewrite_heading_with_level(text: &str, span: Span, new_level: u8) -> Option<String> {
        if !(1..=6).contains(&new_level) {
            return None;
        }
        let segment = &text[span.start.offset..span.end.offset];
        let leading_ws = segment
            .bytes()
            .take_while(|b| *b == b' ' || *b == b'\t')
            .count();
        let after_ws = &segment[leading_ws..];
        let opening = after_ws.bytes().take_while(|b| *b == b'=').count();
        let trimmed_end = after_ws.trim_end_matches([' ', '\t']).len();
        let trailing = after_ws[..trimmed_end]
            .bytes()
            .rev()
            .take_while(|b| *b == b'=')
            .count();
        if opening == 0 || trailing == 0 || opening != trailing {
            return None;
        }
        let middle = &after_ws[opening..trimmed_end - trailing];
        let trailing_ws = &after_ws[trimmed_end..];

        let mut out = String::with_capacity(segment.len() + 2);
        out.push_str(&segment[..leading_ws]);
        for _ in 0..new_level {
            out.push('=');
        }
        out.push_str(middle);
        for _ in 0..new_level {
            out.push('=');
        }
        out.push_str(trailing_ws);
        Some(out)
    }

    /// Find the `[X]` (or other checkbox) substring within a list item's
    /// source span. Returns a span covering exactly the 3-byte run.
    pub fn find_checkbox_span(text: &str, item_span: Span) -> Option<Span> {
        let start = item_span.start.offset;
        let end = item_span.end.offset.min(text.len());
        if start >= end {
            return None;
        }
        let segment = &text[start..end];
        let bytes = segment.as_bytes();
        let mut i = 0;
        while i + 2 < bytes.len() {
            if bytes[i] == b'['
                && bytes[i + 2] == b']'
                && matches!(bytes[i + 1], b' ' | b'.' | b'o' | b'O' | b'X' | b'-')
            {
                let abs_start = start + i;
                let cb_start = nuwiki_core::ast::Position {
                    line: item_span.start.line,
                    column: item_span.start.column + i as u32,
                    offset: abs_start,
                };
                let cb_end = nuwiki_core::ast::Position {
                    line: item_span.start.line,
                    column: item_span.start.column + (i + 3) as u32,
                    offset: abs_start + 3,
                };
                return Some(Span::new(cb_start, cb_end));
            }
            i += 1;
        }
        None
    }

    /// Find the list item whose source line contains `line`. Descends into
    /// sublists; returns the deepest match so editing the inner item works
    /// when the user's cursor sits there.
    pub fn find_list_item_at(ast: &DocumentNode, line: u32, col: u32) -> Option<&ListItemNode> {
        for block in &ast.children {
            if let Some(it) = item_in_block(block, line, col) {
                return Some(it);
            }
        }
        None
    }

    fn item_in_block(block: &BlockNode, line: u32, col: u32) -> Option<&ListItemNode> {
        match block {
            BlockNode::List(l) => l.items.iter().find_map(|it| item_in_list(it, line, col)),
            BlockNode::Blockquote(BlockquoteNode { children, .. }) => {
                children.iter().find_map(|c| item_in_block(c, line, col))
            }
            _ => None,
        }
    }

    fn item_in_list(item: &ListItemNode, line: u32, col: u32) -> Option<&ListItemNode> {
        // Prefer the deepest match: try sublists first.
        if let Some(sub) = &item.sublist {
            for sub_it in &sub.items {
                if let Some(found) = item_in_list(sub_it, line, col) {
                    return Some(found);
                }
            }
        }
        if (item.span.start.line..=item.span.end.line).contains(&line) {
            return Some(item);
        }
        let _ = col;
        None
    }
}