package com.evsuite.abrp;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.view.View;

import java.util.Locale;

/**
 * A round instrument for the dashboard Overview: a 240° scale open at the bottom, major and minor
 * ticks, numbers, a needle, and up to three lines of text in the middle — the unit, the value as
 * digits, and a caption.
 *
 * Drawn on a Canvas with colours resolved from the accent theme, so it needs no gradient
 * drawables (which crash Android 9 with theme colours). A null value draws no needle and a dash:
 * an unread value is never shown as zero. The needle eases towards a new value instead of
 * jumping, and stops redrawing once it is there.
 */
public final class GaugeView extends View {

    private static final float START_DEG = 150f;
    private static final float SWEEP_DEG = 240f;

    private final Paint arc = new Paint(Paint.ANTI_ALIAS_FLAG);
    private final Paint glow = new Paint(Paint.ANTI_ALIAS_FLAG);
    private final Paint tick = new Paint(Paint.ANTI_ALIAS_FLAG);
    private final Paint warnTick = new Paint(Paint.ANTI_ALIAS_FLAG);
    private final Paint number = new Paint(Paint.ANTI_ALIAS_FLAG);
    private final Paint unitPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    private final Paint digits = new Paint(Paint.ANTI_ALIAS_FLAG);
    private final Paint caption = new Paint(Paint.ANTI_ALIAS_FLAG);
    private final Paint needle = new Paint(Paint.ANTI_ALIAS_FLAG);
    private final Paint hub = new Paint(Paint.ANTI_ALIAS_FLAG);
    private final RectF oval = new RectF();

    private float min = 0f, max = 100f, major = 20f;
    private int minorPerMajor = 4;
    private boolean numbers = true;
    private String lowLabel, highLabel;
    private Float warnBelow;
    private String unit = "", valueText = "—", captionText;
    private Float target;
    private float shown = Float.NaN;

    public GaugeView(Context context, AttributeSet attrs) {
        super(context, attrs);
        int accent = AccentColor.resolve(context, R.attr.evAccent);
        int light = AccentColor.resolve(context, R.attr.evAccentLight);
        arc.setStyle(Paint.Style.STROKE);
        arc.setStrokeCap(Paint.Cap.ROUND);
        arc.setColor(accent);
        glow.setStyle(Paint.Style.STROKE);
        glow.setStrokeCap(Paint.Cap.ROUND);
        glow.setColor(AccentColor.withAlpha(accent, 0x40));
        tick.setColor(accent);
        tick.setStrokeCap(Paint.Cap.ROUND);
        warnTick.setColor(0xFFFFB4AB);
        warnTick.setStrokeCap(Paint.Cap.ROUND);
        number.setColor(0xFFF4F3EF);
        number.setTextAlign(Paint.Align.CENTER);
        unitPaint.setColor(0xFFBDC4C6);
        unitPaint.setTextAlign(Paint.Align.CENTER);
        digits.setColor(light);
        digits.setTextAlign(Paint.Align.CENTER);
        digits.setFontFeatureSettings("tnum");
        caption.setColor(0xFFBDC4C6);
        caption.setTextAlign(Paint.Align.CENTER);
        caption.setFontFeatureSettings("tnum");
        needle.setColor(0xFFF4F3EF);
        needle.setStrokeCap(Paint.Cap.ROUND);
        hub.setColor(accent);
    }

    /** The scale: range, spacing of the numbered ticks, and minor ticks between two of them. */
    void configure(float min, float max, float major, int minorPerMajor, String unit) {
        this.min = min;
        this.max = max;
        this.major = major;
        this.minorPerMajor = minorPerMajor;
        this.unit = unit;
        invalidate();
    }

    /** Letters at the two ends (E and F) instead of numbers along the scale. */
    void setEndLabels(String low, String high) {
        lowLabel = low;
        highLabel = high;
        numbers = false;
        invalidate();
    }

    /** Ticks below this value drawn in the warning colour (a low battery). */
    void setWarnBelow(Float value) {
        warnBelow = value;
        invalidate();
    }

    /**
     * The needle's value, null when unread, and its digits ("—" then) and caption. Drawing is
     * left to the next frame, and only the needle animates.
     */
    void setValue(Float value, String valueText, String captionText) {
        target = value == null || !Float.isFinite(value) ? null : value;
        this.valueText = valueText == null ? "—" : valueText;
        this.captionText = captionText;
        if (target != null && Float.isNaN(shown)) shown = target;
        invalidate();
    }

    private float angleOf(float v) {
        float f = (Math.max(min, Math.min(max, v)) - min) / (max - min);
        return START_DEG + SWEEP_DEG * f;
    }

    @Override
    protected void onDraw(Canvas c) {
        super.onDraw(c);
        float w = getWidth(), h = getHeight();
        // Below the centre: the unit, the digits and two caption lines, down to 0.9 r.
        float r = Math.min(w / 2f, h / 1.92f) * 0.95f;
        if (r <= 0f) return;
        float cx = w / 2f, cy = (h - 1.9f * r) / 2f + r;

        float stroke = r * 0.035f;
        arc.setStrokeWidth(stroke);
        glow.setStrokeWidth(stroke * 2.5f);
        oval.set(cx - r, cy - r, cx + r, cy + r);
        c.drawArc(oval, START_DEG, SWEEP_DEG, false, glow);
        c.drawArc(oval, START_DEG, SWEEP_DEG, false, arc);

        // Ticks: every minor step; the numbered ones longer and thicker.
        number.setTextSize(r * 0.105f);
        float minor = major / Math.max(1, minorPerMajor);
        int steps = Math.round((max - min) / minor);
        for (int i = 0; i <= steps; i++) {
            float v = min + i * minor;
            boolean isMajor = i % Math.max(1, minorPerMajor) == 0;
            double a = Math.toRadians(angleOf(v));
            float outer = r * 0.90f, inner = isMajor ? r * 0.76f : r * 0.83f;
            Paint p = warnBelow != null && v < warnBelow ? warnTick : tick;
            p.setStrokeWidth(isMajor ? r * 0.022f : r * 0.012f);
            float cos = (float) Math.cos(a), sin = (float) Math.sin(a);
            c.drawLine(cx + outer * cos, cy + outer * sin, cx + inner * cos, cy + inner * sin, p);
            if (isMajor && numbers) {
                float lr = r * 0.62f;
                c.drawText(String.format(Locale.US, "%.0f", v),
                        cx + lr * cos, cy + lr * sin + number.getTextSize() * 0.36f, number);
            }
        }
        if (!numbers) {
            drawEndLabel(c, cx, cy, r, min, lowLabel, warnBelow != null ? warnTick.getColor() : number.getColor());
            drawEndLabel(c, cx, cy, r, max, highLabel, number.getColor());
        }

        // Under the hub, clear of the needle's sweep: unit, digits, caption.
        unitPaint.setTextSize(r * 0.095f);
        c.drawText(unit, cx, cy + r * 0.25f, unitPaint);
        digits.setTextSize(r * 0.22f);
        c.drawText(valueText, cx, cy + r * 0.50f, digits);
        if (captionText != null) {
            caption.setTextSize(r * 0.09f);
            float y = cy + r * 0.68f;
            for (String line : captionText.split("\n")) {
                c.drawText(line, cx, y, caption);
                y += caption.getTextSize() * 1.25f;
            }
        }

        if (target != null) {
            shown += (target - shown) * 0.25f;
            if (Math.abs(target - shown) < (max - min) * 0.001f) shown = target;
            double a = Math.toRadians(angleOf(shown));
            needle.setStrokeWidth(r * 0.03f);
            c.drawLine(cx, cy, cx + r * 0.80f * (float) Math.cos(a), cy + r * 0.80f * (float) Math.sin(a), needle);
            c.drawCircle(cx, cy, r * 0.065f, hub);
            if (shown != target) postInvalidateOnAnimation();
        } else {
            c.drawCircle(cx, cy, r * 0.065f, hub);
        }
    }

    private void drawEndLabel(Canvas c, float cx, float cy, float r, float v, String label, int color) {
        if (label == null) return;
        double a = Math.toRadians(angleOf(v));
        float lr = r * 0.62f;
        int old = number.getColor();
        number.setColor(color);
        number.setTextSize(r * 0.16f);
        c.drawText(label, cx + lr * (float) Math.cos(a), cy + lr * (float) Math.sin(a) + number.getTextSize() * 0.36f, number);
        number.setColor(old);
    }
}