// TRACES: NFR-A11Y-3
//! No status is told apart by hue alone.
//!
//! NFR-A11Y-3 was built into four controls — the rating strip, the
//! pick/reject mark, the focus-peaking colour chips and the colour labels —
//! and argued in comments beside each, with nothing to fail if a later edit
//! made one of them differ only in tint. An edit like that compiles, renders
//! well to most eyes, and passes every other test.
//!
//! So this reads the markup, for the reason `ui_controls_are_accessible.rs`
//! does: there is no way to ask a rendered Slint window what a colour-blind
//! reader would see, and the property worth defending is structural. For each
//! control it asserts that **what varies with the state is something other
//! than colour** — a glyph's name, a letter, a word — and that the glyphs so
//! named really are different drawings.

use std::fs;
use std::path::Path;

fn ui(file: &str) -> String {
    let path = Path::new(env!("CARGO_MANIFEST_DIR")).join("ui").join(file);
    fs::read_to_string(&path).unwrap_or_else(|e| panic!("cannot read {}: {e}", path.display()))
}

/// The body of one top-level component or global, from its header to the
/// next top-level declaration. The same rule `ui_controls_are_accessible.rs`
/// uses: everything here is declared at column zero.
fn body<'a>(source: &'a str, name: &str) -> &'a str {
    let is_header = |line: &str| {
        let l = line.trim_start_matches("export ");
        l.starts_with("component ") || l.starts_with("global ") || l.starts_with("struct ")
    };
    let declared = |line: &str| {
        line.trim_start_matches("export ")
            .split_whitespace()
            .nth(1)
            .map(str::to_string)
    };
    let mut offset = 0;
    let mut start = None;
    for line in source.lines() {
        if is_header(line) {
            match start {
                None if declared(line).as_deref() == Some(name) => start = Some(offset),
                Some(from) => return &source[from..offset],
                None => {}
            }
        }
        offset += line.len() + 1;
    }
    let from = start.unwrap_or_else(|| panic!("no component `{name}`"));
    &source[from..]
}

/// Code lines only: the prose in these files names the very properties
/// asserted here, and a mention in a comment is not a binding.
fn code_lines(block: &str) -> impl Iterator<Item = &str> {
    block
        .lines()
        .map(str::trim)
        .filter(|l| !l.starts_with("//"))
}

/// Every string literal on a line.
fn literals(line: &str) -> Vec<String> {
    line.split('"')
        .enumerate()
        .filter(|(i, _)| i % 2 == 1)
        .map(|(_, s)| s.to_string())
        .collect()
}

/// The `name:` binding of the `Icon` a component draws its state with — the
/// one line that has to depend on `state`.
fn icon_names_for(block: &str, state: &str) -> Vec<String> {
    let line = code_lines(block)
        .find(|l| l.starts_with("name:") && l.contains(state))
        .unwrap_or_else(|| {
            panic!(
                "no icon's `name:` depends on `{state}` — the state is no longer \
                 carried by which glyph is drawn, only by how it is tinted"
            )
        });
    let mut names = literals(line);
    names.dedup();
    names
}

/// The drawing an icon name selects in icons.slint, less its name line.
fn glyph(name: &str) -> String {
    let icons = ui("icons.slint");
    let header = format!("if root.name == \"{name}\"");
    let from = icons
        .find(&header)
        .unwrap_or_else(|| panic!("icons.slint draws no `{name}`"));
    let rest = &icons[from..];
    let end = rest.find("\n    }").expect("an icon block ends");
    rest[header.len()..end].to_string()
}

/// Two glyph names that are genuinely two drawings.
fn assert_distinct_glyphs(names: &[String], what: &str) {
    assert!(
        names.len() >= 2,
        "{what}: one glyph for every state, so only the tint tells them apart: {names:?}"
    );
    for (i, a) in names.iter().enumerate() {
        for b in &names[i + 1..] {
            assert_ne!(
                glyph(a),
                glyph(b),
                "{what}: `{a}` and `{b}` are the same drawing, so they differ in colour alone"
            );
        }
    }
}

#[test]
fn a_set_star_and_an_unset_one_are_different_shapes() {
    let names = icon_names_for(body(&ui("library.slint"), "StarStrip"), "root.rating");
    assert!(names.contains(&"star".to_string()), "{names:?}");
    assert_distinct_glyphs(&names, "the rating strip");
}

#[test]
fn a_pick_and_a_reject_are_different_shapes() {
    let names = icon_names_for(body(&ui("library.slint"), "FlagMark"), "root.flag");
    assert_distinct_glyphs(&names, "the pick/reject mark");
}

#[test]
fn the_peaking_colours_are_chosen_by_name() {
    // The chips are words, and each word reaches the screen as text.
    let panel = ui("peaking.slint");
    let row = code_lines(&panel)
        .find(|l| l.starts_with("options:") && l.contains("\"Red\""))
        .expect("the peaking colour chips");
    let words = literals(row);
    assert!(words.len() >= 2, "{words:?}");
    let mut unique = words.clone();
    unique.sort();
    unique.dedup();
    assert_eq!(
        unique.len(),
        words.len(),
        "two chips share a word: {words:?}"
    );
    assert!(
        words.iter().all(|w| w.chars().any(char::is_alphabetic)),
        "a chip without a word is a swatch: {words:?}"
    );

    let controls = ui("controls.slint");
    for host in ["Segmented", "ChipGrid"] {
        assert!(
            code_lines(body(&controls, host)).any(|l| l == "label: option;"),
            "{host} no longer hands each option to its chip as a label"
        );
    }
    assert!(
        code_lines(body(&controls, "ChoiceChip")).any(|l| l == "text: root.label;"),
        "ChoiceChip no longer draws its label as text"
    );
}

/// The array bound to `name` in the `Labels` global, by code.
fn labels_array(name: &str) -> Vec<String> {
    let source = ui("labels.slint");
    let line = code_lines(body(&source, "Labels"))
        .find(|l| l.contains(&format!("{name}:")) && l.contains('['))
        .unwrap_or_else(|| panic!("`Labels.{name}` is not an array literal any more"));
    literals(line)
}

#[test]
fn every_colour_label_carries_its_own_letter_and_name() {
    // TRACES: FR-CAT-5
    let letters = labels_array("letters");
    let names = labels_array("names");
    assert_eq!(letters.len(), 6, "none and five labels: {letters:?}");
    assert_eq!(names.len(), 6, "{names:?}");

    let marked = &letters[1..];
    assert!(
        marked.iter().all(|l| !l.trim().is_empty()),
        "a label with no letter is told apart by its fill alone: {letters:?}"
    );
    let mut unique = marked.to_vec();
    unique.sort();
    unique.dedup();
    assert_eq!(unique.len(), 5, "two labels share a letter: {letters:?}");

    // The codes are the catalog's, and each name is the colour that code
    // stores — so the word a chip says is the label it filters on.
    use dr_types::ColourLabel::*;
    for (label, word) in [
        (Red, "Red"),
        (Yellow, "Yellow"),
        (Green, "Green"),
        (Blue, "Blue"),
        (Purple, "Purple"),
    ] {
        let code = dr_catalog::rating::label_code(label) as usize;
        assert_eq!(names[code], word);
        assert!(
            word.starts_with(&letters[code]),
            "{word} is marked {}",
            letters[code]
        );
    }
}

#[test]
fn the_label_mark_draws_the_letter_and_every_label_surface_uses_it() {
    // TRACES: FR-CAT-5
    let labels = ui("labels.slint");
    assert!(
        code_lines(body(&labels, "LabelMark"))
            .any(|l| l.starts_with("text:") && l.contains("Labels.letters[root.code]")),
        "LabelMark no longer draws its label's letter"
    );
    // The picker names every choice in words beside the mark.
    assert!(
        code_lines(body(&labels, "LabelPicker"))
            .any(|l| l.starts_with("text:") && l.contains("Labels.names[code]")),
        "LabelPicker's choices lost their names"
    );

    // Each place a label is shown draws the mark, never a bare fill.
    let library = ui("library.slint");
    assert!(
        library.contains("code: cell.label;"),
        "the grid cell no longer draws its label with LabelMark"
    );
    let widgets = ui("widgets.slint");
    assert!(
        code_lines(body(&widgets, "FilterChip")).any(|l| l == "code: root.colour-label;"),
        "the label chips no longer draw the mark"
    );
    let develop = ui("develop.slint");
    assert!(
        develop.contains("Labels.names[root.colour-label]"),
        "develop no longer names the open photograph's label in words"
    );
}