//! Does the TUI's whole-grid `GridCache` dominate a frame? See improvise-i5tk,
//! improvise-jmjz and `context/code/command.md`. `cargo bench --bench grid_projection`.

use std::time::{Duration, Instant};

use improvise::format::FormatPlan;
use improvise::model::cell::{CellKey, CellValue};
use improvise::view::{Axis, GridLayout};
use improvise::workbook::Workbook;
use improvise_command::ui::app::App;
use improvise_command::ui::project::{self, Viewport};
use improvise_command::ui::viewport::compute_col_widths;

/// A dense pivot grid: `regions * products` rows by `measures` columns, every
/// cell filled, which is the worst case for a per-cell evaluation.
fn dense_app(regions: usize, products: usize, measures: usize) -> App {
    let mut wb = Workbook::new("Bench");
    wb.add_category("Region").unwrap();
    wb.add_category("Product").unwrap();
    let region_names: Vec<String> = (0..regions).map(|i| format!("Region{i}")).collect();
    let product_names: Vec<String> = (0..products).map(|i| format!("Product{i}")).collect();
    let measure_names: Vec<String> = (0..measures).map(|i| format!("Measure{i}")).collect();
    for r in &region_names {
        wb.add_item("Region", r.clone()).unwrap();
    }
    for p in &product_names {
        wb.add_item("Product", p.clone()).unwrap();
    }
    for m in &measure_names {
        wb.add_item("_Measure", m.clone()).unwrap();
    }
    {
        let v = wb.active_view_mut();
        v.set_axis("Region", Axis::Row);
        v.set_axis("Product", Axis::Row);
        v.set_axis("_Measure", Axis::Column);
    }
    let mut n = 0.0f64;
    for r in &region_names {
        for p in &product_names {
            for m in &measure_names {
                n += 1.0;
                let key = CellKey::new(vec![
                    ("Region".to_string(), r.clone()),
                    ("Product".to_string(), p.clone()),
                    ("_Measure".to_string(), m.clone()),
                ]);
                wb.model.set_cell(key, CellValue::Number(n));
            }
        }
    }
    let mut app = App::new(wb, None);
    app.rebuild_layout();
    app
}

/// Collapsed groups on the row axis and a formula chain on the column axis, so
/// every fold cell and every total re-derives the chain (improvise-h6z1).
fn chain_app(regions: usize, products: usize) -> App {
    let mut wb = Workbook::new("Chain");
    wb.add_category("Region").unwrap();
    wb.add_category("Product").unwrap();
    for r in 0..regions {
        wb.add_item_in_group("Region", format!("Region{r}"), format!("G{}", r / 10))
            .unwrap();
    }
    for p in 0..products {
        wb.add_item("Product", format!("Product{p}")).unwrap();
    }
    wb.add_item("_Measure", "Revenue").unwrap();
    let chain = [
        "F1 = Revenue * 2",
        "F2 = F1 + Revenue",
        "F3 = F2 + F1",
        "F4 = F3 + F2",
        "F5 = F4 / F1",
    ];
    for text in chain {
        let formula = improvise::formula::parse_formula(text, "_Measure").unwrap();
        wb.model.add_formula(formula);
    }
    {
        let v = wb.active_view_mut();
        v.set_axis("Region", Axis::Row);
        v.set_axis("Product", Axis::Row);
        v.set_axis("_Measure", Axis::Column);
    }
    let mut n = 0.0f64;
    for r in 0..regions {
        for p in 0..products {
            n += 1.0;
            let key = CellKey::new(vec![
                ("Region".to_string(), format!("Region{r}")),
                ("Product".to_string(), format!("Product{p}")),
                ("_Measure".to_string(), "Revenue".to_string()),
            ]);
            wb.model.set_cell(key, CellValue::Number(n));
        }
    }
    let mut app = App::new(wb, None);
    app.rebuild_layout();
    app
}

/// Days in collapsed groups of `per_group` on Row, with Product: every row is a
/// fold over a few days, never the whole category (improvise-jq0m).
fn grouped_app(days: usize, per_group: usize, products: usize, measures: usize) -> App {
    let mut wb = Workbook::new("Grouped");
    wb.add_category("Day").unwrap();
    wb.add_category("Product").unwrap();
    for d in 0..days {
        let group = format!("G{}", d / per_group);
        wb.add_item_in_group("Day", format!("Day{d}"), group)
            .unwrap();
    }
    for p in 0..products {
        wb.add_item("Product", format!("Product{p}")).unwrap();
    }
    for m in 0..measures {
        wb.add_item("_Measure", format!("Measure{m}")).unwrap();
    }
    {
        let v = wb.active_view_mut();
        v.set_axis("Day", Axis::Row);
        v.set_axis("Product", Axis::Row);
        v.set_axis("_Measure", Axis::Column);
    }
    let mut n = 0.0f64;
    for d in 0..days {
        for p in 0..products {
            for m in 0..measures {
                n += 1.0;
                let key = CellKey::new(vec![
                    ("Day".to_string(), format!("Day{d}")),
                    ("Product".to_string(), format!("Product{p}")),
                    ("_Measure".to_string(), format!("Measure{m}")),
                ]);
                wb.model.set_cell(key, CellValue::Number(n));
            }
        }
    }
    let mut app = App::new(wb, None);
    app.rebuild_layout();
    app
}

fn whole_grid(app: &App) -> Viewport {
    Viewport {
        row_offset: 0,
        col_offset: 0,
        rows: app.layout.row_count(),
        cols: app.layout.col_count(),
    }
}

/// A terminal window: what the TUI would ask for if a cache position were
/// relative, which is the browser client's arrangement.
fn terminal_window() -> Viewport {
    Viewport {
        row_offset: 0,
        col_offset: 0,
        rows: 45,
        cols: 12,
    }
}

/// Min-of-N, not the mean: a mean over a handful of iterations is dominated by
/// whatever else the machine was doing, which is how a share above 100% happens.
fn time(iters: u32, app: &App, viewport: Viewport) -> Duration {
    let mut best = Duration::MAX;
    for _ in 0..iters.max(3) {
        let start = Instant::now();
        std::hint::black_box(project::grid_of(app, viewport));
        best = best.min(start.elapsed());
    }
    best
}

/// `compute_col_widths` is whole-grid whatever the viewport says, so it is the part
/// narrowing the cells loop cannot reach. It must be timed with the arguments
/// `grid_of` passes it, or the share is of a call that never happens.
// Since improvise-jmjz it IS the fused walk, with an empty window, so its share
// rose while the frame fell: it is now the work, not the redundancy.
fn time_widths(iters: u32, app: &App) -> Duration {
    let layout = &app.layout;
    let model = &app.model_state.workbook.model;
    let plan = FormatPlan::of(model, app.model_state.workbook.active_view());
    let mut best = Duration::MAX;
    for _ in 0..iters.max(3) {
        let start = Instant::now();
        std::hint::black_box(compute_col_widths(model, layout, &plan));
        best = best.min(start.elapsed());
    }
    best
}

fn case(label: &str, regions: usize, products: usize, measures: usize, iters: u32) {
    report(label, dense_app(regions, products, measures), iters);
}

fn report(label: &str, app: App, iters: u32) {
    let rows = app.layout.row_count();
    let cols = app.layout.col_count();
    let cells = rows * cols;
    let full = time(iters, &app, whole_grid(&app));
    let windowed = time(iters, &app, terminal_window());
    let widths = time_widths(iters, &app);
    let ratio = full.as_secs_f64() / windowed.as_secs_f64().max(f64::EPSILON);
    let share = 100.0 * widths.as_secs_f64() / full.as_secs_f64().max(f64::EPSILON);
    // A part cannot take longer than the whole that contains it. Say so rather
    // than printing a number that reads like a measurement.
    let share = match share > 100.0 {
        true => "UNSTABLE".to_string(),
        false => format!("{share:.0}%"),
    };
    // The TUI pays both on every keypress: widths in `cmd_context`, the grid in draw.
    let keypress = full + widths;
    println!(
        "{label:<22} {rows:>5} x {cols:>3} = {cells:>7} cells  whole-grid {full:>11.3?}  \
windowed {windowed:>11.3?}  ratio {ratio:>4.1}x  col_widths {widths:>11.3?} ({share} of the frame)  \
keypress {keypress:>11.3?}"
    );
}

/// The layout build with `prune_empty` on: every cell evaluated to find the empty
/// rows and columns, on the same keypress path as `grid_of` (improvise-metf).
fn report_prune(label: &str, mut app: App, iters: u32) {
    app.model_state.workbook.active_view_mut().prune_empty = true;
    let model = &app.model_state.workbook.model;
    let view = app.model_state.workbook.active_view();
    let mut best = Duration::MAX;
    for _ in 0..iters.max(3) {
        let start = Instant::now();
        std::hint::black_box(GridLayout::with_frozen_records(model, view, None));
        best = best.min(start.elapsed());
    }
    println!("{label:<22} layout build with prune_empty {best:>11.3?}");
}

fn main() {
    println!("project::grid_of, one call = one TUI frame's grid cache");
    println!("a 60fps frame budget is 16.7ms; the TUI redraws on each keypress\n");
    case("typical", 20, 5, 4, 200);
    case("1.2k cells", 60, 5, 4, 100);
    case("2.4k cells", 60, 10, 4, 100);
    case("4.8k cells", 60, 20, 4, 50);
    case("large", 60, 20, 8, 50);
    case("18k cells (gotcha 41)", 150, 20, 6, 20);
    case("pathological", 300, 30, 10, 5);
    println!("\nfolded rows and a five-formula chain (improvise-h6z1)\n");
    report("folded chain ~18k", chain_app(1000, 30), 5);
    report("folded chain ~90k", chain_app(5000, 30), 3);
    println!("\nthe same, pruned (improvise-metf)\n");
    report_prune("dense 18k", dense_app(150, 20, 6), 5);
    report_prune("folded chain ~18k", chain_app(1000, 30), 5);
    report_prune("folded chain ~90k", chain_app(5000, 30), 3);
    println!("\ncollapsed small groups on the row axis (improvise-jq0m)\n");
    report("364 days in weeks", grouped_app(364, 7, 20, 6), 5);
    report("364 days in pairs", grouped_app(364, 2, 20, 6), 5);
    report("1000 days in pairs", grouped_app(1000, 2, 10, 4), 3);
}