/*
 * Copyright (c) 2014-2017, Eren Okka
 * Copyright (c) 2016-2017, Paul Miller
 * Copyright (c) 2017-2018, Tyler Bratton
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/.
 */

namespace AnitomySharp;

/// <summary>
/// Class to classify <see cref="Token"/>s
/// </summary>
public class Parser
{
    public bool IsEpisodeKeywordsFound { get; private set; }
    public ParserHelper ParseHelper { get; }
    public ParserNumber ParseNumber { get; }
    public List<Element> Elements { get; }
    public List<Token> Tokens { get; }
    private Options Options { get; }

    /// <summary>
    /// Constructs a new token parser
    /// </summary>
    /// <param name="elements">the list where parsed elements will be added</param>
    /// <param name="options">the parser options</param>
    /// <param name="tokens">the list of tokens</param>
    public Parser(List<Element> elements, Options options, List<Token> tokens)
    {
        Elements = elements;
        Options = options;
        Tokens = tokens;
        ParseHelper = new ParserHelper(this);
        ParseNumber = new ParserNumber(this);
    }

    /** Begins the parsing process */
    public bool Parse()
    {
        SearchForKeywords();
        SearchForIsolatedNumbers();

        if (Options.ParseEpisodeNumber)
        {
            SearchForEpisodeNumber();
        }

        SearchForAnimeTitle();

        if (Options.ParseReleaseGroup && Empty(ElementCategory.ElementReleaseGroup))
        {
            SearchForReleaseGroup();
        }

        if (Options.ParseEpisodeTitle && !Empty(ElementCategory.ElementEpisodeNumber))
        {
            SearchForEpisodeTitle();
        }

        ValidateElements();
        return Empty(ElementCategory.ElementAnimeTitle);
    }

    /** Search for anime keywords. */
    private void SearchForKeywords()
    {
        for (int i = 0; i < Tokens.Count; i++)
        {
            var token = Tokens[i];
            if (token.Category != Token.TokenCategory.Unknown) continue;

            string word = token.Content;
            word = word.Trim(" -".ToCharArray());
            if (string.IsNullOrEmpty(word)) continue;

            // Don't bother if the word is a number that cannot be CRC
            if (word.Length != 8 && StringHelper.IsNumericString(word)) continue;

            string keyword = KeywordManager.Normalize(word);
            var category = ElementCategory.ElementUnknown;
            var options = new KeywordOptions();

            if (KeywordManager.FindAndSet(keyword, ref category, ref options))
            {
                if (!Options.ParseReleaseGroup && category == ElementCategory.ElementReleaseGroup) continue;
                if (!ParserHelper.IsElementCategorySearchable(category) || !options.Searchable) continue;
                if (ParserHelper.IsElementCategorySingular(category) && !Empty(category)) continue;
                switch (category)
                {
                    case ElementCategory.ElementAnimeSeasonPrefix:
                        ParseHelper.CheckAndSetAnimeSeasonKeyword(token, i);
                        continue;
                    case ElementCategory.ElementEpisodePrefix when options.Valid:
                        ParseHelper.CheckExtentKeyword(ElementCategory.ElementEpisodeNumber, i, token);
                        continue;
                    case ElementCategory.ElementReleaseVersion:
                        word = word[1..];
                        break;
                    case ElementCategory.ElementVolumePrefix:
                        ParseHelper.CheckExtentKeyword(ElementCategory.ElementVolumeNumber, i, token);
                        continue;
                }
            }
            else
            {
                if (Empty(ElementCategory.ElementFileChecksum) && ParserHelper.IsCrc32(word))
                {
                    category = ElementCategory.ElementFileChecksum;
                }
                else if (Empty(ElementCategory.ElementVideoResolution) && ParserHelper.IsResolution(word))
                {
                    category = ElementCategory.ElementVideoResolution;
                }
            }

            if (category == ElementCategory.ElementUnknown) continue;
            Elements.Add(new Element(category, word));
            if (options.Identifiable)
            {
                token.Category = Token.TokenCategory.Identifier;
            }
        }
    }

    /** Search for episode number. */
    private void SearchForEpisodeNumber()
    {
        // List all unknown tokens that contain a number
        var tokens = new List<int>();
        for (int i = 0; i < Tokens.Count; i++)
        {
            var token = Tokens[i];
            if (token.Category == Token.TokenCategory.Unknown &&
                ParserHelper.IndexOfFirstDigit(token.Content) != -1)
            {
                tokens.Add(i);
            }
        }

        if (tokens.Count == 0) return;

        IsEpisodeKeywordsFound = !Empty(ElementCategory.ElementEpisodeNumber);

        // If a token matches a known episode pattern, it has to be the episode number
        if (ParseNumber.SearchForEpisodePatterns(tokens)) return;

        // We have previously found an episode number via keywords
        if (!Empty(ElementCategory.ElementEpisodeNumber)) return;

        // From now on, we're only interested in numeric tokens
        tokens.RemoveAll(r => !StringHelper.IsNumericString(Tokens[r].Content));

        // e.g. "01 (176)", "29 (04)"
        if (ParseNumber.SearchForEquivalentNumbers(tokens)) return;

        // e.g. " - 08"
        if (ParseNumber.SearchForSeparatedNumbers(tokens)) return;

        // "e.g. "[12]", "(2006)"
        if (ParseNumber.SearchForIsolatedNumbers(tokens)) return;

        // Consider using the last number as a last resort
        ParseNumber.SearchForLastNumber(tokens);
    }

    /// <summary>
    /// Search for anime title
    /// </summary>
    private void SearchForAnimeTitle()
    {
        bool enclosedTitle = false;

        int tokenBegin = Token.FindToken(Tokens, 0, Tokens.Count, Token.TokenFlag.FlagNotEnclosed,
            Token.TokenFlag.FlagUnknown);

        // If that doesn't work, find the first unknown token in the second enclosed
        // group, assuming that the first one is the release group
        if (!Token.InListRange(tokenBegin, Tokens))
        {
            tokenBegin = 0;
            enclosedTitle = true;
            bool skippedPreviousGroup = false;

            do
            {
                tokenBegin = Token.FindToken(Tokens, tokenBegin, Tokens.Count, Token.TokenFlag.FlagUnknown);
                if (!Token.InListRange(tokenBegin, Tokens)) break;

                // Ignore groups that are composed of non-Latin characters
                if (StringHelper.IsMostlyLatinString(Tokens[tokenBegin].Content) && skippedPreviousGroup)
                {
                    break;
                }

                // Get the first unknown token of the next group
                tokenBegin = Token.FindToken(Tokens, tokenBegin, Tokens.Count, Token.TokenFlag.FlagBracket);
                tokenBegin = Token.FindToken(Tokens, tokenBegin, Tokens.Count, Token.TokenFlag.FlagUnknown);
                skippedPreviousGroup = true;
            } while (Token.InListRange(tokenBegin, Tokens));
        }

        if (!Token.InListRange(tokenBegin, Tokens)) return;

        // Continue until an identifier (or a bracket, if the title is enclosed) is found
        int tokenEnd = Token.FindToken(
            Tokens,
            tokenBegin,
            Tokens.Count,
            Token.TokenFlag.FlagIdentifier,
            enclosedTitle ? Token.TokenFlag.FlagBracket : Token.TokenFlag.FlagNone);

        // If within the interval there's an open bracket without its matching pair,
        // move the upper endpoint back to the bracket
        if (!enclosedTitle)
        {
            int lastBracket = tokenEnd;
            bool bracketOpen = false;
            for (int i = tokenBegin; i < tokenEnd; i++)
            {
                if (Tokens[i].Category != Token.TokenCategory.Bracket) continue;
                lastBracket = i;
                bracketOpen = !bracketOpen;
            }

            if (bracketOpen) tokenEnd = lastBracket;
        }

        // If the interval ends with an enclosed group (e.g. "Anime Title [Fansub]"),
        // move the upper endpoint back to the beginning of the group. We ignore
        // parentheses in order to keep certain groups (e.g. "(TV)") intact.
        if (!enclosedTitle)
        {
            int token = Token.FindPrevToken(Tokens, tokenEnd, Token.TokenFlag.FlagNotDelimiter);

            while (ParseHelper.IsTokenCategory(token, Token.TokenCategory.Bracket) && Tokens[token].Content[0] != ')')
            {
                token = Token.FindPrevToken(Tokens, token, Token.TokenFlag.FlagBracket);
                if (!Token.InListRange(token, Tokens)) continue;
                tokenEnd = token;
                token = Token.FindPrevToken(Tokens, tokenEnd, Token.TokenFlag.FlagNotDelimiter);
            }
        }

        ParseHelper.BuildElement(ElementCategory.ElementAnimeTitle, false,
            Tokens.GetRange(tokenBegin, tokenEnd - tokenBegin));
    }

    /// <summary>
    /// Search for release group
    /// </summary>
    private void SearchForReleaseGroup()
    {
        for (int tokenBegin = 0, tokenEnd = tokenBegin; tokenBegin < Tokens.Count;)
        {
            // Find the first enclosed unknown token
            tokenBegin = Token.FindToken(Tokens, tokenEnd, Tokens.Count, Token.TokenFlag.FlagEnclosed,
                Token.TokenFlag.FlagUnknown);
            if (!Token.InListRange(tokenBegin, Tokens)) return;

            // Continue until a bracket or identifier is found
            tokenEnd = Token.FindToken(Tokens, tokenBegin, Tokens.Count, Token.TokenFlag.FlagBracket,
                Token.TokenFlag.FlagIdentifier);
            if (!Token.InListRange(tokenEnd, Tokens) ||
                Tokens[tokenEnd].Category != Token.TokenCategory.Bracket) continue;

            // Ignore if it's not the first non-delimiter token in group
            int prevToken = Token.FindPrevToken(Tokens, tokenBegin, Token.TokenFlag.FlagNotDelimiter);
            if (Token.InListRange(prevToken, Tokens) &&
                Tokens[prevToken].Category != Token.TokenCategory.Bracket) continue;

            ParseHelper.BuildElement(ElementCategory.ElementReleaseGroup, true,
                Tokens.GetRange(tokenBegin, tokenEnd - tokenBegin));
            return;
        }
    }

    /// <summary>
    /// Search for episode title
    /// </summary>
    private void SearchForEpisodeTitle()
    {
        int tokenBegin;
        int tokenEnd = 0;

        do
        {
            // Find the first non-enclosed unknown token
            tokenBegin = Token.FindToken(Tokens, tokenEnd, Tokens.Count, Token.TokenFlag.FlagNotEnclosed,
                Token.TokenFlag.FlagUnknown);
            if (!Token.InListRange(tokenBegin, Tokens)) return;

            // Continue until a bracket or identifier is found
            tokenEnd = Token.FindToken(Tokens, tokenBegin, Tokens.Count, Token.TokenFlag.FlagBracket,
                Token.TokenFlag.FlagIdentifier);

            // Ignore if it's only a dash
            if (tokenEnd - tokenBegin <= 2 && ParserHelper.IsDashCharacter(Tokens[tokenBegin].Content[0])) continue;
            //if (tokenBegin.Pos == null || tokenEnd.Pos == null) continue;
            ParseHelper.BuildElement(ElementCategory.ElementEpisodeTitle, false,
                Tokens.GetRange(tokenBegin, tokenEnd - tokenBegin));
            return;
        } while (Token.InListRange(tokenBegin, Tokens));
    }

    /// <summary>
    /// Search for isolated numbers
    /// </summary>
    private void SearchForIsolatedNumbers()
    {
        for (int i = 0; i < Tokens.Count; i++)
        {
            var token = Tokens[i];
            if (token.Category != Token.TokenCategory.Unknown || !StringHelper.IsNumericString(token.Content) ||
                !ParseHelper.IsTokenIsolated(i))
            {
                continue;
            }

            int number = StringHelper.StringToInt(token.Content);

            // Anime year
            if (number >= ParserNumber.AnimeYearMin && number <= ParserNumber.AnimeYearMax)
            {
                if (Empty(ElementCategory.ElementAnimeYear))
                {
                    Elements.Add(new Element(ElementCategory.ElementAnimeYear, token.Content));
                    token.Category = Token.TokenCategory.Identifier;
                    continue;
                }
            }

            // Video resolution
            if (number != 480 && number != 720 && number != 1080) continue;
            // If these numbers are isolated, it's more likely for them to be the
            // video resolution rather than the episode number. Some fansub groups use these without the "p" suffix.
            if (!Empty(ElementCategory.ElementVideoResolution)) continue;
            Elements.Add(new Element(ElementCategory.ElementVideoResolution, token.Content));
            token.Category = Token.TokenCategory.Identifier;
        }
    }

    /// <summary>
    /// Validate Elements
    /// </summary>
    private void ValidateElements()
    {
        if (Empty(ElementCategory.ElementAnimeType) || Empty(ElementCategory.ElementEpisodeTitle))
        {
            return;
        }

        string episodeTitle = Get(ElementCategory.ElementEpisodeTitle);

        for (int i = 0; i < Elements.Count;)
        {
            var el = Elements[i];

            if (el.Category == ElementCategory.ElementAnimeType)
            {
                if (episodeTitle.Contains(el.Value))
                {
                    if (episodeTitle.Length == el.Value.Length)
                    {
                        Elements.RemoveAll(element =>
                            element.Category == ElementCategory.ElementEpisodeTitle); // invalid episode title
                    }
                    else
                    {
                        string keyword = KeywordManager.Normalize(el.Value);
                        if (KeywordManager.Contains(ElementCategory.ElementAnimeType, keyword))
                        {
                            i = Erase(el); // invalid anime type
                            continue;
                        }
                    }
                }
            }

            ++i;
        }
    }

    /// <summary>
    /// Returns whether or not the parser contains this category
    /// </summary>
    /// <param name="category"></param>
    /// <returns></returns>
    private bool Empty(ElementCategory category)
    {
        return Elements.All(element => element.Category != category);
    }

    /// <summary>
    /// Returns the value of a particular category
    /// </summary>
    /// <param name="category"></param>
    /// <returns></returns>
    private string Get(ElementCategory category)
    {
        var foundElement = Elements.Find(element => element.Category == category);

        if (foundElement != null) return foundElement.Value;
        Element e = new Element(category, "");
        Elements.Add(e);
        foundElement = e;

        return foundElement.Value;
    }

    /// <summary>
    /// Deletes the first element with the same <code>element.Category</code> and returns the deleted element's position.
    /// </summary>
    private int Erase(Element element)
    {
        int removedIdx = -1;
        for (int i = 0; i < Elements.Count; i++)
        {
            var currentElement = Elements[i];
            if (element.Category != currentElement.Category) continue;
            removedIdx = i;
            Elements.RemoveAt(i);
            break;
        }

        return removedIdx;
    }
}