deepseek-tui 0.6.5

//! `@`-mention parsing, completion, and expansion for the composer.
//!
//! Two responsibilities live here:
//!
//! 1. **Tab-completion** at the cursor — `try_autocomplete_file_mention` is
//!    called by the composer's Tab handler. Walks the workspace, ranks
//!    candidates by prefix-then-substring match, and either splices the
//!    completion in directly (single match), extends to a shared prefix, or
//!    surfaces options in the status line.
//! 2. **Expansion before send** — when the user hits Enter on a message that
//!    contains `@<path>` references, `user_request_with_file_mentions`
//!    appends a "Local context from @mentions" block with the file contents
//!    (or directory listings, or media-attachment hints) so the model can see
//!    what the user pointed at. Capped per-message and per-file.
//!
//! The module is deliberately self-contained: nothing inside reaches into UI
//! widgets or rendering, so it stays unit-testable from `ui/tests.rs` and
//! from its own module-level tests.
//!
//! Pulled out of `ui.rs` to shrink the 5,500-line monolith and to give the
//! mention logic a single home that future maintainers can find without
//! grepping for `@` across half the codebase.

use std::fmt::Write;
use std::io::Read;
use std::path::Path;

use ignore::WalkBuilder;

use crate::tui::app::App;
use crate::working_set::Workspace;

/// Maximum number of `@`-mentions whose contents are inlined into one user
/// message. Beyond this we stop appending blocks but the raw `@token` text
/// remains in the message.
pub const MAX_FILE_MENTIONS_PER_MESSAGE: usize = 8;
/// Per-file byte ceiling when inlining mention contents.
pub const MAX_MENTION_FILE_BYTES: u64 = 128 * 1024;
/// Per-directory entry ceiling when inlining a directory listing.
pub const MAX_DIRECTORY_MENTION_ENTRIES: usize = 80;

/// Maximum file-mention completion candidates to consider per keypress. Caps
/// the cost of walking large workspaces; subsequent keystrokes narrow further.
const FILE_MENTION_COMPLETION_LIMIT: usize = 64;

/// Maximum directory depth walked when completing a file mention. Mirrors the
/// existing `project_tree` cutoff and keeps Tab snappy in deep monorepos.
const FILE_MENTION_COMPLETION_DEPTH: usize = 6;

// ---------------------------------------------------------------------------
//  Tab-completion
// ---------------------------------------------------------------------------

/// If the cursor sits inside a `@<partial>` token in the input, return the
/// byte offset where the `@` starts (so we can splice in a completion) and
/// the partial path the user has typed so far. The token stops at whitespace
/// or the end of input. Returns `None` when the cursor is outside any mention
/// or the token is empty (`@` with nothing after it).
pub fn partial_file_mention_at_cursor(input: &str, cursor_chars: usize) -> Option<(usize, String)> {
    let chars: Vec<char> = input.chars().collect();
    if cursor_chars > chars.len() {
        return None;
    }
    // Walk left from the cursor until we find an `@` or a whitespace; if
    // whitespace comes first the cursor isn't inside a mention.
    let mut start_chars = cursor_chars;
    while start_chars > 0 {
        let prev = chars[start_chars - 1];
        if prev == '@' {
            start_chars -= 1;
            break;
        }
        if prev.is_whitespace() {
            return None;
        }
        start_chars -= 1;
    }
    if start_chars == cursor_chars || chars.get(start_chars) != Some(&'@') {
        return None;
    }
    // Confirm the `@` itself is at a valid mention boundary.
    if !is_file_mention_start(&chars, start_chars) {
        return None;
    }
    // Consume from the `@` to the next whitespace (the end of the token).
    let mut end_chars = start_chars + 1;
    while end_chars < chars.len() && !chars[end_chars].is_whitespace() {
        end_chars += 1;
    }
    let partial: String = chars[start_chars + 1..end_chars].iter().collect();
    let byte_start: usize = chars[..start_chars].iter().map(|c| c.len_utf8()).sum();
    Some((byte_start, partial))
}

/// Walk the workspace and return relative paths whose representation matches
/// the partial mention. A file matches when its case-insensitive relative
/// path either starts with the partial or contains it as a substring; the
/// former rank earlier so a partial like `docs/de` resolves to
/// `docs/deepseek_v4.pdf` before any path that merely contains those bytes.
pub fn find_file_mention_completions(workspace: &Path, partial: &str, limit: usize) -> Vec<String> {
    if limit == 0 {
        return Vec::new();
    }
    let needle = partial.to_lowercase();
    let mut prefix_hits: Vec<String> = Vec::new();
    let mut substring_hits: Vec<String> = Vec::new();

    let mut builder = WalkBuilder::new(workspace);
    builder
        .hidden(true)
        .follow_links(false)
        .max_depth(Some(FILE_MENTION_COMPLETION_DEPTH));

    for entry in builder.build().flatten() {
        if prefix_hits.len() + substring_hits.len() >= limit {
            break;
        }
        let path = entry.path();
        let Ok(rel) = path.strip_prefix(workspace) else {
            continue;
        };
        let rel_str = rel.to_string_lossy().replace('\\', "/");
        if rel_str.is_empty() {
            continue;
        }
        let is_dir = entry.file_type().is_some_and(|ft| ft.is_dir());
        let candidate = if is_dir {
            format!("{rel_str}/")
        } else {
            rel_str.clone()
        };
        let lower = candidate.to_lowercase();
        if needle.is_empty() || lower.starts_with(&needle) {
            prefix_hits.push(candidate);
        } else if lower.contains(&needle) {
            substring_hits.push(candidate);
        }
    }

    prefix_hits.sort();
    substring_hits.sort();
    prefix_hits.extend(substring_hits);
    prefix_hits.truncate(limit);
    prefix_hits
}

/// Resolve the `@`-mention completion popup contents for the current
/// composer state. Returns an empty `Vec` when:
///
/// - The popup is suppressed (`app.mention_menu_hidden`).
/// - The cursor is not inside an `@<partial>` token.
/// - The workspace walk produced no candidates.
///
/// Mirrors `visible_slash_menu_entries` so the composer widget can treat
/// both menus identically (one `Vec<String>` of entries, one selected index).
///
/// Once the composer widget is extended to render this as a popup, it will
/// pair with `apply_mention_menu_selection` for the Up/Down/Enter flow.
#[must_use]
pub fn visible_mention_menu_entries(app: &App, limit: usize) -> Vec<String> {
    if app.mention_menu_hidden {
        return Vec::new();
    }
    let Some((_byte_start, partial)) =
        partial_file_mention_at_cursor(&app.input, app.cursor_position)
    else {
        return Vec::new();
    };
    if limit == 0 {
        return Vec::new();
    }
    find_file_mention_completions(&app.workspace, &partial, limit)
}

/// Apply the currently selected `@`-mention popup entry to the composer
/// input, splicing it in place of the `@<partial>` token at the cursor.
/// Returns `true` if a substitution occurred.
///
/// Designed to be invoked by the same keybinding that drives
/// `apply_slash_menu_selection` (Enter / Tab); the caller is responsible
/// for choosing which menu is "active" based on cursor context.
pub fn apply_mention_menu_selection(app: &mut App, entries: &[String]) -> bool {
    if entries.is_empty() {
        return false;
    }
    let Some((byte_start, partial)) =
        partial_file_mention_at_cursor(&app.input, app.cursor_position)
    else {
        return false;
    };
    let selected_idx = app
        .mention_menu_selected
        .min(entries.len().saturating_sub(1));
    let replacement = &entries[selected_idx];
    replace_file_mention(app, byte_start, &partial, replacement);
    app.mention_menu_hidden = false;
    app.status_message = Some(format!("Attached @{replacement}"));
    true
}

/// Tab-completion handler for `@file` mentions. Mirrors the slash-command
/// flow: a single match is applied directly; multiple matches with a longer
/// shared prefix extend the partial; otherwise the first few candidates are
/// surfaced via the status line. Returns true when the input was modified or
/// a suggestion was offered, so the caller can short-circuit other handlers.
pub fn try_autocomplete_file_mention(app: &mut App) -> bool {
    let Some((byte_start, partial)) =
        partial_file_mention_at_cursor(&app.input, app.cursor_position)
    else {
        return false;
    };
    let workspace = app.workspace.clone();
    let candidates =
        find_file_mention_completions(&workspace, &partial, FILE_MENTION_COMPLETION_LIMIT);
    if candidates.is_empty() {
        app.status_message = Some(format!("No files match @{partial}"));
        return true;
    }
    if candidates.len() == 1 {
        replace_file_mention(app, byte_start, &partial, &candidates[0]);
        app.status_message = Some(format!("Attached @{}", candidates[0]));
        return true;
    }
    let candidate_refs: Vec<&str> = candidates.iter().map(String::as_str).collect();
    let shared = longest_common_prefix(&candidate_refs);
    if shared.len() > partial.len() {
        replace_file_mention(app, byte_start, &partial, shared);
        app.status_message = Some(format!("@{shared}…"));
        return true;
    }
    let preview = candidates
        .iter()
        .take(5)
        .map(|c| format!("@{c}"))
        .collect::<Vec<_>>()
        .join(", ");
    app.status_message = Some(format!("Matches: {preview}"));
    true
}

/// Splice a completion into the input, replacing the `@<partial>` token at
/// `byte_start` with `@<replacement>`. Cursor moves to the end of the new
/// token so further keystrokes extend (or escape via space) naturally.
fn replace_file_mention(app: &mut App, byte_start: usize, partial: &str, replacement: &str) {
    let original_token_len = '@'.len_utf8() + partial.len();
    let original_token_end = byte_start + original_token_len;
    let mut new_input =
        String::with_capacity(app.input.len() - original_token_len + 1 + replacement.len());
    new_input.push_str(&app.input[..byte_start]);
    new_input.push('@');
    new_input.push_str(replacement);
    if original_token_end < app.input.len() {
        new_input.push_str(&app.input[original_token_end..]);
    }
    let new_cursor_chars =
        app.input[..byte_start].chars().count() + 1 + replacement.chars().count();
    app.input = new_input;
    app.cursor_position = new_cursor_chars;
}

pub fn longest_common_prefix<'a>(values: &[&'a str]) -> &'a str {
    let Some(first) = values.first().copied() else {
        return "";
    };
    let mut end = first.len();

    for value in values.iter().skip(1) {
        while end > 0 && !value.starts_with(&first[..end]) {
            end -= 1;
            // Ensure we land on a valid UTF-8 char boundary.
            while end > 0 && !first.is_char_boundary(end) {
                end -= 1;
            }
        }
        if end == 0 {
            return "";
        }
    }

    &first[..end]
}

// ---------------------------------------------------------------------------
//  Expansion at send-time
// ---------------------------------------------------------------------------

/// Append a "Local context from @mentions" block to the user's message when
/// any `@path` references are present. Returns the input unchanged when
/// there are none.
pub fn user_request_with_file_mentions(input: &str, workspace: &Path) -> String {
    let Some(context) = local_context_from_file_mentions(input, workspace) else {
        return input.to_string();
    };
    format!("{input}\n\n---\n\nLocal context from @mentions:\n{context}")
}

fn local_context_from_file_mentions(input: &str, workspace: &Path) -> Option<String> {
    let mentions = extract_file_mentions(input);
    if mentions.is_empty() {
        return None;
    }

    let mut blocks = Vec::new();
    let mut seen = std::collections::HashSet::new();
    let ws = Workspace::new(workspace.to_path_buf());

    for mention in mentions.into_iter().take(MAX_FILE_MENTIONS_PER_MESSAGE) {
        // `Workspace::resolve` already returns absolute paths when the root
        // is absolute (TUI always runs from an absolute workspace), so we
        // skip `canonicalize()` here — it's per-mention I/O on the
        // message-send hot path. Accept the rare symlink-aliasing dedup
        // miss as the cost of avoiding a syscall (Gemini code-review).
        let (path, display_path, exists) = match ws.resolve(&mention) {
            Ok(p) => {
                let d = p.display().to_string();
                (p, d, true)
            }
            Err(p) => {
                let d = p.display().to_string();
                (p, d, false)
            }
        };

        // Gate every block — including <missing-file> — through the dedup
        // set so a user typing the same non-existent file twice doesn't
        // waste tokens on duplicate missing-file blocks (Devin code-review).
        if !seen.insert(display_path.clone()) {
            continue;
        }

        if exists {
            blocks.push(render_file_mention_context(&mention, &path, &display_path));
        } else {
            blocks.push(format!(
                "<missing-file mention=\"@{mention}\" path=\"{display_path}\" />"
            ));
        }
    }

    if blocks.is_empty() {
        None
    } else {
        Some(blocks.join("\n\n"))
    }
}

fn extract_file_mentions(input: &str) -> Vec<String> {
    let chars: Vec<char> = input.chars().collect();
    let mut mentions = Vec::new();
    let mut idx = 0;

    while idx < chars.len() {
        if chars[idx] != '@' || !is_file_mention_start(&chars, idx) {
            idx += 1;
            continue;
        }

        let Some(next) = chars.get(idx + 1).copied() else {
            break;
        };
        if next.is_whitespace() {
            idx += 1;
            continue;
        }

        if matches!(next, '"' | '\'') {
            let quote = next;
            let mut end = idx + 2;
            let mut raw = String::new();
            while end < chars.len() && chars[end] != quote {
                raw.push(chars[end]);
                end += 1;
            }
            if !raw.trim().is_empty() {
                mentions.push(raw.trim().to_string());
            }
            idx = end.saturating_add(1);
            continue;
        }

        let mut end = idx + 1;
        let mut raw = String::new();
        while end < chars.len() && !chars[end].is_whitespace() {
            raw.push(chars[end]);
            end += 1;
        }
        let trimmed = trim_unquoted_mention(&raw);
        if !trimmed.is_empty() {
            mentions.push(trimmed.to_string());
        }
        idx = end;
    }

    mentions
}

fn is_file_mention_start(chars: &[char], idx: usize) -> bool {
    if idx == 0 {
        return true;
    }
    chars
        .get(idx.saturating_sub(1))
        .is_some_and(|ch| ch.is_whitespace() || matches!(ch, '(' | '[' | '{' | '<' | '"' | '\''))
}

fn trim_unquoted_mention(raw: &str) -> &str {
    let mut trimmed = raw.trim();
    while trimmed.chars().count() > 1
        && trimmed
            .chars()
            .last()
            .is_some_and(|ch| matches!(ch, ',' | ';' | ':' | '!' | '?' | ')' | ']' | '}'))
    {
        trimmed = &trimmed[..trimmed.len() - trimmed.chars().last().unwrap().len_utf8()];
    }
    trimmed
}

fn render_file_mention_context(raw: &str, path: &Path, display_path: &str) -> String {
    if !path.exists() {
        return format!("<missing-file mention=\"@{raw}\" path=\"{display_path}\" />");
    }
    if path.is_dir() {
        return render_directory_mention_context(raw, path, display_path);
    }
    if !path.is_file() {
        return format!("<unsupported-path mention=\"@{raw}\" path=\"{display_path}\" />");
    }
    if is_media_path(path) {
        return format!(
            "<media-file mention=\"@{raw}\" path=\"{display_path}\">\nUse /attach {raw} when the intent is to attach this image or video to the next message.\n</media-file>"
        );
    }

    match read_text_prefix(path) {
        Ok((text, truncated)) => {
            let truncated_attr = if truncated { " truncated=\"true\"" } else { "" };
            format!(
                "<file mention=\"@{raw}\" path=\"{display_path}\"{truncated_attr}>\n{text}\n</file>"
            )
        }
        Err(err) => {
            format!(
                "<unreadable-file mention=\"@{raw}\" path=\"{display_path}\">\n{err}\n</unreadable-file>"
            )
        }
    }
}

fn render_directory_mention_context(raw: &str, path: &Path, display_path: &str) -> String {
    let entries = match std::fs::read_dir(path) {
        Ok(entries) => entries,
        Err(err) => {
            return format!(
                "<unreadable-directory mention=\"@{raw}\" path=\"{display_path}\">\n{err}\n</unreadable-directory>"
            );
        }
    };

    let mut names = entries
        .filter_map(|entry| entry.ok())
        .map(|entry| {
            let marker = entry
                .file_type()
                .ok()
                .filter(|ty| ty.is_dir())
                .map_or("", |_| "/");
            format!("{}{}", entry.file_name().to_string_lossy(), marker)
        })
        .collect::<Vec<_>>();
    names.sort();
    let total = names.len();
    names.truncate(MAX_DIRECTORY_MENTION_ENTRIES);
    let mut body = names.join("\n");
    if total > MAX_DIRECTORY_MENTION_ENTRIES {
        let omitted = total - MAX_DIRECTORY_MENTION_ENTRIES;
        let _ = write!(body, "\n... {omitted} more entries");
    }
    format!("<directory mention=\"@{raw}\" path=\"{display_path}\">\n{body}\n</directory>")
}

fn read_text_prefix(path: &Path) -> std::io::Result<(String, bool)> {
    let mut file = std::fs::File::open(path)?;
    let mut buffer = Vec::new();
    file.by_ref()
        .take(MAX_MENTION_FILE_BYTES + 1)
        .read_to_end(&mut buffer)?;
    let truncated = buffer.len() as u64 > MAX_MENTION_FILE_BYTES;
    if truncated {
        buffer.truncate(MAX_MENTION_FILE_BYTES as usize);
    }
    if buffer.contains(&0) {
        return Err(std::io::Error::new(
            std::io::ErrorKind::InvalidData,
            "file appears to be binary",
        ));
    }
    let text = if truncated {
        String::from_utf8_lossy(&buffer).to_string()
    } else {
        std::str::from_utf8(&buffer)
            .map_err(|_| std::io::Error::new(std::io::ErrorKind::InvalidData, "file is not UTF-8"))?
            .to_string()
    };
    Ok((text, truncated))
}

fn is_media_path(path: &Path) -> bool {
    let Some(ext) = path.extension().and_then(|ext| ext.to_str()) else {
        return false;
    };
    matches!(
        ext.to_ascii_lowercase().as_str(),
        "png"
            | "jpg"
            | "jpeg"
            | "gif"
            | "webp"
            | "bmp"
            | "tif"
            | "tiff"
            | "ppm"
            | "mp4"
            | "mov"
            | "m4v"
            | "webm"
            | "avi"
            | "mkv"
    )
}