// TRACES: NFR-A11Y-2
//! Every shared control says what it is, and every slider says what it edits.
//!
//! NFR-A11Y-2 asks that controls expose names, roles and values to AT-SPI and
//! TalkBack. Almost none of that is Rust: it is `accessible-*` properties in
//! Slint markup, which no unit test can observe by running the interface —
//! there is no accessibility tree without a window, and CI has no display.
//!
//! So this reads the markup, the way `darkroom-android`'s manifest test reads
//! the XML that aapt2 owns and rustc never sees. The property being defended
//! is not "the screen reader announces the right words", which needs a device
//! and a person; it is the thing that silently regresses instead — **a control
//! losing its role or its name in an ordinary refactor**, which compiles,
//! renders identically, passes every other test, and is invisible to anyone
//! not using a screen reader. That failure has already happened once here: the
//! whole application had five `accessible-*` lines in 14,482 lines of markup,
//! all of them on one row of the colour mixer, and nothing said so.
//!
//! ## What is checked, and what deliberately is not
//!
//! Two properties, both structural:
//!
//! 1. **Named components declare the roles they promise.** A `Button` that
//!    stops declaring `accessible-role` stops existing for a screen reader
//!    entirely, because Slint rejects every other `accessible-*` property that
//!    is not accompanied by a role — so the role is the load-bearing one and
//!    the rest fail with it.
//!
//! 2. **Every `SliderTrack` instantiation supplies a `label`.** This is the
//!    one that catches a *new* control rather than a broken old one. The track
//!    cannot name itself — it has no idea what number it is dragging — so an
//!    unnamed one announces "slider, 0.35" and is the single most-used control
//!    in the application. A track added without a label is the exact mistake
//!    this file exists to make loud.
//!
//! Not checked: whether the words are good, whether they are translated,
//! whether contrast passes, or whether Android exposes any of it — spike S13
//! is still unrun and no test on this side of it can answer that.

use std::fs;
use std::path::{Path, PathBuf};

/// A component that must carry particular `accessible-*` properties, and the
/// properties it must carry.
///
/// Only the ones whose absence is a behavioural loss are listed. `Button` must
/// declare `accessible-action-default` because without it a screen reader can
/// read the button and not press it, which is a control that exists and cannot
/// be used; it need not declare `accessible-description`, which is a nicety.
struct Promise {
    file: &'static str,
    component: &'static str,
    properties: &'static [&'static str],
}

const PROMISES: &[Promise] = &[
    Promise {
        file: "widgets.slint",
        component: "Button",
        properties: &["accessible-role", "accessible-label", "accessible-action-default"],
    },
    Promise {
        file: "widgets.slint",
        component: "IconButton",
        properties: &["accessible-role", "accessible-label", "accessible-action-default"],
    },
    Promise {
        file: "widgets.slint",
        component: "FilterChip",
        properties: &[
            "accessible-role",
            "accessible-label",
            "accessible-checked",
            "accessible-action-default",
        ],
    },
    Promise {
        file: "widgets.slint",
        component: "Section",
        properties: &["accessible-role", "accessible-label", "accessible-expanded"],
    },
    Promise {
        file: "widgets.slint",
        component: "ProgressBar",
        properties: &["accessible-role", "accessible-label", "accessible-value"],
    },
    // The label goes on the `TextInput` inside, not on the box around it —
    // Slint gives that element its role, so the name belongs beside it.
    Promise {
        file: "widgets.slint",
        component: "Field",
        properties: &["accessible-label", "accessible-placeholder-text"],
    },
    Promise {
        file: "controls.slint",
        component: "SliderTrack",
        properties: &[
            "accessible-role",
            "accessible-label",
            "accessible-value",
            "accessible-value-minimum",
            "accessible-value-maximum",
            "accessible-action-increment",
            "accessible-action-decrement",
            "accessible-action-set-value",
        ],
    },
    Promise {
        file: "controls.slint",
        component: "Check",
        properties: &[
            "accessible-role",
            "accessible-label",
            "accessible-checked",
            "accessible-action-default",
        ],
    },
    Promise {
        file: "controls.slint",
        component: "ChoiceChip",
        properties: &[
            "accessible-role",
            "accessible-label",
            "accessible-checked",
            "accessible-action-default",
        ],
    },
];

fn ui_dir() -> PathBuf {
    Path::new(env!("CARGO_MANIFEST_DIR")).join("ui")
}

fn read(path: &Path) -> String {
    fs::read_to_string(path).unwrap_or_else(|e| panic!("cannot read {}: {e}", path.display()))
}

/// The body of one top-level component declaration, or `None` if the file
/// declares no such component.
///
/// Every component in these files is declared at column zero, so the block
/// runs from its header to the next header or to the end of the file. A
/// looser rule than brace matching and a stricter one than "somewhere in the
/// file": the point is that a property found for `Button` really is inside
/// `Button` and not inside the component below it.
fn component_body<'a>(source: &'a str, name: &str) -> Option<&'a str> {
    let header_starts = |line: &str| {
        line.starts_with("component ") || line.starts_with("export component ")
    };

    let mut start = None;
    for (offset, line) in line_offsets(source) {
        if !header_starts(line) {
            continue;
        }
        // `component Foo inherits Bar {` — the word after `component`.
        let declared = line
            .trim_start_matches("export ")
            .trim_start_matches("component ")
            .split_whitespace()
            .next();

        match start {
            None if declared == Some(name) => start = Some(offset),
            Some(from) => return Some(&source[from..offset]),
            None => {}
        }
    }
    start.map(|from| &source[from..])
}

/// Each line of `source` with its byte offset.
fn line_offsets(source: &str) -> impl Iterator<Item = (usize, &str)> {
    let mut offset = 0;
    source.lines().map(move |line| {
        let at = offset;
        offset += line.len() + 1;
        (at, line)
    })
}

/// Whether a block sets a property — the name at the start of a line, followed
/// by what Slint puts after a name it is binding to.
///
/// Three forms, and the third is easy to forget: `name:` for a property,
/// `name =>` for a callback, and `name(arg) =>` for a callback that takes one.
/// `accessible-action-set-value` is the only member of the third group here and
/// leaving it out made this test report the slider as missing the very action
/// it declares.
///
/// Anchored at the start of the trimmed line so that a *mention* in the prose
/// above a component does not count. These files carry more comment than code,
/// and several of those comments name the very properties asserted here; a
/// substring search would pass on the strength of an explanation of the thing
/// that had been deleted, which is the failure `ui_names_no_operation.rs`
/// documents at length and the android manifest test strips comments to avoid.
fn sets(block: &str, property: &str) -> bool {
    block.lines().any(|line| {
        let line = line.trim_start();
        line.strip_prefix(property).is_some_and(|rest| {
            let rest = rest.trim_start();
            rest.starts_with(':') || rest.starts_with("=>") || rest.starts_with('(')
        })
    })
}

#[test]
fn shared_controls_declare_their_roles() {
    let ui = ui_dir();
    let mut failures = Vec::new();

    for promise in PROMISES {
        let path = ui.join(promise.file);
        let source = read(&path);

        let Some(body) = component_body(&source, promise.component) else {
            failures.push(format!(
                "  {} declares no component `{}` — it was renamed or removed, and \
                 this test then checks nothing",
                promise.file, promise.component
            ));
            continue;
        };

        for property in promise.properties {
            if !sets(body, property) {
                failures.push(format!(
                    "  {}: `{}` does not set `{property}`",
                    promise.file, promise.component
                ));
            }
        }
    }

    assert!(
        failures.is_empty(),
        "\n\nNFR-A11Y-2: controls expose names, roles and values to the platform \
         accessibility layer.\n\n{}\n\n\
         Slint rejects every `accessible-*` property that is not accompanied by an \
         `accessible-role`, so the role is what makes the control exist for AT-SPI \
         and TalkBack at all, and the actions are what make it usable rather than \
         merely readable.\n\n\
         These live on the shared components rather than at the call sites \
         deliberately: a control annotated where it is used is a control unnamed \
         everywhere it is used next. See the preamble to widgets.slint.\n",
        failures.join("\n")
    );
}

#[test]
fn every_slider_track_is_named() {
    let ui = ui_dir();
    let mut files: Vec<PathBuf> = fs::read_dir(&ui)
        .unwrap_or_else(|e| panic!("cannot read {}: {e}", ui.display()))
        .map(|entry| entry.expect("read dir entry").path())
        .filter(|p| p.extension().and_then(|e| e.to_str()) == Some("slint"))
        .collect();
    files.sort();

    let mut instantiations = 0usize;
    let mut unnamed = Vec::new();

    for path in &files {
        let source = read(path);
        let name = path.file_name().and_then(|n| n.to_str()).unwrap_or("?");

        // The declaration itself, in controls.slint, is not an instantiation.
        for (offset, line) in line_offsets(&source) {
            if line.trim_start() != "SliderTrack {" {
                continue;
            }
            instantiations += 1;

            let block = &source[offset..offset + block_len(&source[offset..])];
            if !sets(block, "label") {
                let number = source[..offset].lines().count() + 1;
                unnamed.push(format!("  {name}:{number}"));
            }
        }
    }

    // A scan that found nothing passes for the wrong reason. Four tracks are
    // instantiated today — the develop panel's three shapes and the settings
    // page's row — and the floor sits below that and well above zero, so
    // removing one is a code change and not a silent scan failure.
    assert!(
        instantiations >= 3,
        "found only {instantiations} `SliderTrack` instantiations — the scan is \
         matching nothing, and a scan over nothing passes"
    );

    assert!(
        unnamed.is_empty(),
        "\n\nNFR-A11Y-2: a slider that does not say what it adjusts.\n\n{}\n\n\
         `SliderTrack` cannot name itself — it is handed four numbers and knows \
         nothing about what they mean — so a track without a `label` announces as \
         \"slider, 0.35\". The develop column holds thirty-six of them in the \
         colour mixer alone, which is thirty-six controls a screen reader cannot \
         tell apart.\n\n\
         Pass the same string the row is already drawing above the track.\n",
        unnamed.join("\n")
    );
}

/// The length of the brace-delimited block beginning at the start of `rest`,
/// including both braces.
///
/// Braces inside string literals are not handled, and do not occur inside a
/// `SliderTrack` instantiation — the only strings there are labels and units.
fn block_len(rest: &str) -> usize {
    let mut depth = 0usize;
    for (i, c) in rest.char_indices() {
        match c {
            '{' => depth += 1,
            '}' => {
                depth -= 1;
                if depth == 0 {
                    return i + 1;
                }
            }
            _ => {}
        }
    }
    rest.len()
}