using System;
using System.Collections.Generic;
using Godot;

namespace Haikuchatclient {

    public static class PixelTools {

        // Find out message height in pixels.
        // **********************************
        // Can be used to set surrounding elements of Labels etc. to a proper height.
        public static int GetPixelHeightForText(string text, DynamicFont dynamicFont, int surroundingElementWidth) {

            // Get line height in pixels, ie. font height. It's always standard AFAIK.
            var fontHeight = dynamicFont.GetHeight();

            // Split the text into an array using spaces as delimiters - and include the spaces.
            var splitText = SplitAndKeepDelimiters(text, " ");

            // Calculate how many lines of text there will be.
            var lineCount = CalculateLines(splitText, dynamicFont, surroundingElementWidth);
            
            // Calculate the pixel height needed to fit in the text.
            var pixelHeight = lineCount * fontHeight;// + lineSpacing;

            // Account for the outline surrounding the font.
            pixelHeight += (dynamicFont.OutlineSize * lineCount);
            
            // Return the result.
            return (int) pixelHeight;
        }

        
        /// <summary>
        /// Splits the given string into a list of substrings, while outputting the splitting
        /// delimiters (each in its own string) as well. It's just like String.Split() except
        /// the delimiters are preserved. No empty strings are output.</summary>
        /// <param name="s">String to parse. Can be null or empty.</param>
        /// <param name="delimiters">The delimiting strings. Can be an empty array.</param>
        /// <returns></returns>
        public static IList<string> SplitAndKeepDelimiters(string s, params string[] delimiters) {

            var parts = new List<string>() { s };

            if (!string.IsNullOrEmpty(s)) {

                foreach (string delimiter in delimiters) { // Delimiter counter.
					
                    for (int i = 0; i < parts.Count; i++) { // Part counter.
					
                        int index = parts[i].IndexOf(delimiter, StringComparison.Ordinal);

                        if (index > -1 && parts[i].Length > index + 1) {
                            string leftPart = parts[i].Substring(0, index + delimiter.Length);
                            string rightPart = parts[i].Substring(index + delimiter.Length);
                            parts[i] = leftPart;
                            parts.Insert(i + 1, rightPart);
                        }
                    }
                }
            } 
            return parts;
        }

        
        private static int CalculateLines(IList<string> splitText, DynamicFont dynamicFont, int surroundingElementWidth) {

            // Keeps track how much pixels we have left before we need to wrap to a next line.
            var widthLeftUntilNextLine = surroundingElementWidth;

            // Get last index position so we can refer to it.
            var lastIndex = splitText.Count - 1;

            // We need to keep track of the current index so we know when we hit the last one - so we can add last line.
            var indexCounter = 0;

            // We start from line 1, because there is always at least one line.
            var totalLines = 1;

            // Iterate through the split message to find out the amount of lines the message will split to.
            foreach (var word in splitText) {

                // Let's find out how many pixels there are in this word.
                var pixelsInWord = GetWordPixelWidth(word, dynamicFont);
                
                // If the amount of pixels is more than one line can handle we go to the next line.
                if (pixelsInWord > widthLeftUntilNextLine) {
                    totalLines += 1;

                    // TODO: Code will bug out if the word is too long. One way to handle it is to do manual line breaks. 
                    // Subtract this word's width from the next line because this word didn't fit on last line.
                    widthLeftUntilNextLine = surroundingElementWidth - pixelsInWord;

                    // We can handle some more words. No line break yet.
                } else if (pixelsInWord == widthLeftUntilNextLine) {
                    // Prevent border case where we don't need the extra line.
                    if (indexCounter != lastIndex) {
                        totalLines += 1;
                    }

                    widthLeftUntilNextLine = surroundingElementWidth;
                } else {
                    // Reduce the word's length from the pixels left for this line.
                    widthLeftUntilNextLine -= pixelsInWord;
                }

                // Increase the index for the next round.
                indexCounter += 1;
            }

            return totalLines;
        }

        
        // Return the total width of a string in pixels.
        // TODO: Could this be turned into an extension method?
        public static int GetWordPixelWidth(string word, DynamicFont dynamicFont) {
            return (int) dynamicFont.GetStringSize(word).x;
        }
        
    }
}