package com.gh.common.view;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Rect;
import android.os.Build;
import android.text.Layout;
import android.text.SpannableStringBuilder;
import android.text.Spanned;
import android.text.TextPaint;
import android.text.style.ClickableSpan;
import android.util.AttributeSet;
import android.view.View;

import com.gh.gamecenter.R;

import androidx.annotation.NonNull;
import androidx.appcompat.widget.AppCompatTextView;
import androidx.core.content.ContextCompat;

public class ExpandTextView extends AppCompatTextView {
    
    private CharSequence mSnapshotText;
    
    private String mEndText = "...";
    private String mExpandText = mEndText + "全文";
    private boolean mUseGradientAlphaEndText = false;
    private boolean mShrinkOnAnchor = false; // 以锚点所在的位置进行收起 (即 maxLines = 锚点所在的行)
    
    private int mMaxLines = 3; // 由于sdk版本限制(getMaxLines) 这里设置默认值
    
    private boolean mInitLayout = false;
    private boolean mIsExpanded = false; // 位于 recyclerView 时需要自行在外层管理是否已展开
    
    private ExpandCallback mExpandCallback;
    private SelfCalculateMaxLinesCallback mMaxLinesCalculatedCallback;
    
    private Rect mLastVisibleLineRect;
    private Rect mLastActualLineRect;
    
    private static int DEFAULT_ADDITIONAL_END_TEXT_COUNT = 2;
    public static final String SHRINK_ANCHOR = "☼";
    
    public ExpandTextView(Context context) {
        super(context);
    }
    
    public ExpandTextView(Context context, AttributeSet attrs) {
        super(context, attrs);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
            mMaxLines = getMaxLines();
        }
        
        mLastVisibleLineRect = new Rect();
        mLastActualLineRect = new Rect();
        
        TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.ExpandTextView);
        mShrinkOnAnchor = ta.getBoolean(R.styleable.ExpandTextView_shrinkOnAnchor, false);
        mUseGradientAlphaEndText = ta.getBoolean(R.styleable.ExpandTextView_useGradientAlphaEndText, false);
        mEndText = ta.getString(R.styleable.ExpandTextView_endText) == null ? mEndText : ta.getString(R.styleable.ExpandTextView_endText);
        mExpandText = ta.getString(R.styleable.ExpandTextView_expandText) == null ? mExpandText : ta
            .getString(R.styleable.ExpandTextView_expandText);
        ta.recycle();
    }
    
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        if (mShrinkOnAnchor && getText().toString().contains(SHRINK_ANCHOR)) {
            updateMaxLinesByShrinkAnchor();
        }
        setMeasuredDimension(getMeasuredWidth(), getMeasuredHeight() - getExtraBottomPadding());
    }
    
    private void updateMaxLinesByShrinkAnchor() {
        int lineCount = getLineCount();
        for (int line = 0; line < lineCount; line++) {
            CharSequence substring = getText().subSequence(getLayout().getLineStart(line), getLayout().getLineEnd(line));
            if (substring.toString().contains(SHRINK_ANCHOR)) {
                if (mMaxLines != line + 1) {
                    if (!mIsExpanded) {
                        setExpandMaxLines(line + 1);
                        mMaxLinesCalculatedCallback.onMaxLinesCalculated(line + 1);
                    }
                    setText(findAndDeleteAnchor(getText()));
                    break;
                }
            }
        }
    }
    
    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
        if (mInitLayout && !mIsExpanded && getLineCount() > mMaxLines) {
            mSnapshotText = findAndDeleteAnchor(getText());
            mInitLayout = false;
            showExpandButton();
        }
    }
    
    public void setExpandText(String text) {
        this.mExpandText = text;
    }
    
    public void setExpandCallback(ExpandCallback callback) {
        this.mExpandCallback = callback;
    }
    
    @Override
    public void setText(CharSequence text, BufferType type) {
        mInitLayout = true;
        super.setText(text, type);
    }
    
    private void showExpandButton() {
        String finalEndText = "";
        TextPaint paint = getPaint();
        
        Layout layout = getLayout();
        int start = layout.getLineStart(0);
        int lastLineEnd = layout.getLineEnd(mMaxLines - 1);
        int lastLineStart = layout.getLineStart(mMaxLines - 1);
        float lastLineRight = layout.getLineRight(mMaxLines - 1);
        
        int viewWidth = getWidth() - getPaddingRight() - getPaddingLeft();
        int additionalEndTextCount = 0;
        
        float expandTextWidth;
        if (mUseGradientAlphaEndText) {
            additionalEndTextCount = DEFAULT_ADDITIONAL_END_TEXT_COUNT;
            expandTextWidth = paint.measureText(mEndText + mExpandText);
        } else {
            expandTextWidth = paint.measureText(mExpandText);
        }
        
        CharSequence content = mSnapshotText.subSequence(start, lastLineEnd);
        
        if (viewWidth - lastLineRight > expandTextWidth) {
            if (mUseGradientAlphaEndText) {
                finalEndText = content.toString()
                    .substring(content.length() - additionalEndTextCount, content.length()) + mEndText;
                finalEndText = finalEndText.replace("\n", "");
                
                content = content.subSequence(0, content.length() - additionalEndTextCount) + finalEndText + mExpandText;
            } else {
                content = content.toString().trim() + mExpandText;
            }
        } else {
            CharSequence lastLineText = mSnapshotText.subSequence(lastLineStart, lastLineEnd);
            CharSequence subSequence;
            float subSequenceWidth;
            for (int i = lastLineText.length() - 1; i > 0; i--) {
                if (mUseGradientAlphaEndText) {
                    subSequence = lastLineText.subSequence(0, i - additionalEndTextCount);
                    subSequenceWidth = paint.measureText(subSequence.toString());
                    
                    finalEndText = lastLineText.subSequence(i - additionalEndTextCount, i) + mEndText;
                    expandTextWidth = paint.measureText(finalEndText + mExpandText);
                    
                    if (viewWidth - subSequenceWidth > expandTextWidth) {
                        finalEndText = finalEndText.replace("\n", "");
                        content = mSnapshotText.subSequence(start, lastLineStart + i - additionalEndTextCount) + finalEndText + mExpandText;
                        break;
                    }
                } else {
                    subSequence = lastLineText.subSequence(0, i);
                    subSequenceWidth = paint.measureText(subSequence.toString());
                    
                    if (viewWidth - subSequenceWidth > expandTextWidth) {
                        content = mSnapshotText.subSequence(start, lastLineStart + i) + mExpandText;
                        break;
                    }
                }
            }
        }
        
        SpannableStringBuilder msp = new SpannableStringBuilder(mSnapshotText);
        int length = msp.length();
        int startPosition;
        startPosition = content.length() - finalEndText.length() - mExpandText.length();
        startPosition = Math.max(startPosition, 0);
        
        // 避免越界
        if (startPosition >= length) return;
        
        msp.replace(startPosition, length, finalEndText + mExpandText);
        
        msp.setSpan(new ClickableSpan() {
            @Override
            public void updateDrawState(@NonNull TextPaint ds) {
                super.updateDrawState(ds);
                ds.setColor(ContextCompat.getColor(getContext(), R.color.theme_font));
                ds.setUnderlineText(false);
            }
            
            @Override
            public void onClick(@NonNull View widget) {
                mIsExpanded = true;
                setMaxLines(Integer.MAX_VALUE);
                setText(mSnapshotText);
                
                if (mExpandCallback != null) {
                    mExpandCallback.onExpand();
                }
            }
        }, startPosition + mEndText.length(), msp.length(), Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
        msp.setSpan(new GradientAlphaTextSpan(), startPosition, startPosition + finalEndText.length(), Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
        
        setText(msp);
        setMovementMethod(CustomLinkMovementMethod.getInstance());
    }
    
    /**
     * 获取 maxLines + lineSpacingExtra + movementMethod 一起使用时产生的大小与 lineSpacingExtra 一样的底部空间
     */
    private int getExtraBottomPadding() {
        int result = 0;
        // 界面上显示的最后一行的 index
        int lastVisibleLineIndex = Math.min(getMaxLines(), getLineCount()) - 1;
        // 获取实际文字的最后一行的 index
        int lastActualLineIndex = getLineCount() - 1;
        
        if (lastVisibleLineIndex >= 0) {
            Layout layout = getLayout();
            int lastVisibleLineBaseline = getLineBounds(lastVisibleLineIndex, mLastVisibleLineRect);
            getLineBounds(lastActualLineIndex, mLastActualLineRect);
            int heightBetweenLastVisibleLineRectAndLastActualLineRect = (mLastActualLineRect.bottom - mLastVisibleLineRect.bottom);
            
            if (getMeasuredHeight() == getLayout().getHeight() - heightBetweenLastVisibleLineRectAndLastActualLineRect) {
                result = mLastVisibleLineRect.bottom - (lastVisibleLineBaseline + layout.getPaint()
                    .getFontMetricsInt().descent + getPaddingBottom());
                if (getLineSpacingExtra() > result) {
                    result = 0;
                } else {
                    result = (int) getLineSpacingExtra();
                }
            }
        }
        return result;
    }
    
    // 去掉锚点
    private CharSequence findAndDeleteAnchor(CharSequence charSequence) {
        int anchorIndex = charSequence.toString().indexOf(SHRINK_ANCHOR);
        if (anchorIndex >= 0) {
            SpannableStringBuilder sb = new SpannableStringBuilder(getText());
            sb.delete(anchorIndex, anchorIndex + 1);
            return sb;
        } else {
            return charSequence;
        }
    }
    
    /**
     * 此方法仅更改标记，不做实际展开的操作
     */
    public void setIsExpanded(boolean isExpanded) {
        mIsExpanded = isExpanded;
    }
    
    public void setExpandMaxLines(int maxLines) {
        mMaxLines = maxLines;
        setMaxLines(maxLines);
    }
    
    public void setSelfCalculateMaxLinesCallback(SelfCalculateMaxLinesCallback callback) {
        mMaxLinesCalculatedCallback = callback;
    }
    
    public interface ExpandCallback {
        void onExpand();
    }
    
    public interface SelfCalculateMaxLinesCallback {
        void onMaxLinesCalculated(int maxLines);
    }
    
}