logViewer/crates/tui/src/app/viewport_cache.rs

use log_viewer_core::types::LogLevel;
use unicode_width::UnicodeWidthChar;

pub(super) struct ViewportEntry {
    pub(super) wrapped_rows: Vec<String>,
    pub(super) level: Option<LogLevel>,
    pub(super) visual_height: usize,
}

pub(super) struct ViewportCache {
    pub(super) entries: Vec<ViewportEntry>,
    pub(super) logical_start: usize,
    pub(super) width: usize,
    json_format: bool,
    pub(super) cached_total_visual_rows: Option<usize>,
}

impl ViewportCache {
    pub(super) fn new() -> Self {
        Self {
            entries: Vec::new(),
            logical_start: 0,
            width: 0,
            json_format: false,
            cached_total_visual_rows: None,
        }
    }

    pub(super) fn invalidate(&mut self) {
        self.entries.clear();
        self.logical_start = 0;
        self.width = 0;
        self.cached_total_visual_rows = None;
    }

    pub(super) fn needs_recompute(&self, width: usize, json_format: bool) -> bool {
        self.width != width || self.json_format != json_format
    }

    pub(super) fn set_json_format(&mut self, json_format: bool) {
        self.json_format = json_format;
    }

    #[allow(dead_code)]
    pub(super) fn get_entry(&self, logical_line: usize) -> Option<&ViewportEntry> {
        if logical_line >= self.logical_start {
            let idx = logical_line - self.logical_start;
            self.entries.get(idx)
        } else {
            None
        }
    }
}

pub(super) const TRUNCATE_TAB_WIDTH: usize = 4;

pub(super) fn gutter_width_for(total_lines: usize, is_loading: bool) -> usize {
    if total_lines == 0 {
        return 0;
    }
    let line_num_width = total_lines.to_string().len();
    let loading_extra = if is_loading { 1 } else { 0 };
    line_num_width + loading_extra + 1 + 1
}

pub(super) fn truncate_to_columns(s: &str, max_cols: usize) -> String {
    if max_cols == 0 || s.is_empty() {
        return String::new();
    }

    let mut out = String::new();
    let mut col = 0;

    for ch in s.chars() {
        if ch == '\t' {
            let tab_stop = TRUNCATE_TAB_WIDTH - (col % TRUNCATE_TAB_WIDTH);
            if col + tab_stop > max_cols {
                break;
            }
            for _ in 0..tab_stop {
                out.push(' ');
            }
            col += tab_stop;
        } else {
            let w = if ch.is_control() {
                0
            } else {
                ch.width().unwrap_or(0)
            };
            if col + w > max_cols {
                break;
            }
            out.push(ch);
            col += w;
        }
    }

    out
}