package org.zwobble.mammoth.internal.docx;

import org.zwobble.mammoth.internal.archives.Archive;
import org.zwobble.mammoth.internal.documents.Comment;
import org.zwobble.mammoth.internal.documents.Document;
import org.zwobble.mammoth.internal.documents.Notes;
import org.zwobble.mammoth.internal.results.InternalResult;
import org.zwobble.mammoth.internal.util.Lists;
import org.zwobble.mammoth.internal.util.PassThroughException;
import org.zwobble.mammoth.internal.xml.XmlElement;

import java.io.IOException;
import java.nio.file.Path;
import java.util.List;
import java.util.Optional;

import static org.zwobble.mammoth.internal.util.Lists.*;
import static org.zwobble.mammoth.internal.util.Strings.trimLeft;

public class DocumentReader {
    @FunctionalInterface
    private interface BodyReaders {
        BodyXmlReader forName(String name);
    }

    public static InternalResult<Document> readDocument(Optional<Path> path, Archive zipFile) {
        Relationships packageRelationships = readPackageRelationships(zipFile);
        String documentFilename = findDocumentFilename(zipFile, packageRelationships);

        Styles styles = readStyles(zipFile);
        Numbering numbering = readNumbering(zipFile);
        ContentTypes contentTypes = readContentTypes(zipFile);
        FileReader fileReader = new PathRelativeFileReader(path);
        BodyReaders bodyReaders = name -> {
            Relationships relationships = readRelationshipsFor(zipFile, name);
            return new BodyXmlReader(styles, numbering, relationships, contentTypes, zipFile, fileReader);
        };
        return InternalResult.flatMap(
            readNotes(zipFile, bodyReaders),
            readComments(zipFile, bodyReaders),
            (notes, comments) -> {
                DocumentXmlReader reader = new DocumentXmlReader(bodyReaders.forName("document"), notes, comments);
                return reader.readElement(parseOfficeXml(zipFile, documentFilename));
            });
    }

    private static Relationships readPackageRelationships(Archive archive) {
        return readRelationships(archive, "_rels/.rels");
    }

    private static String findDocumentFilename(Archive archive, Relationships packageRelationships) {
        String officeDocumentType = "http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument";
        List<String> targets = eagerConcat(
            eagerMap(
                packageRelationships.findTargetsByType(officeDocumentType),
                target -> trimLeft(target, '/')
            ),
            list("word/document.xml")
        );
        List<String> validTargets = eagerFilter(targets, archive::exists);
        return tryGetFirst(validTargets)
            .orElseThrow(() -> new PassThroughException(
                new IOException("Could not find main document part. Are you sure this is a valid .docx file?")
            ));
    }

    private static InternalResult<List<Comment>> readComments(Archive file, BodyReaders bodyReaders) {
        return tryParseOfficeXml(file, "word/comments.xml")
            .map(new CommentXmlReader(bodyReaders.forName("comments"))::readElement)
            .orElse(InternalResult.success(list()));
    }

    private static InternalResult<Notes> readNotes(Archive file, BodyReaders bodyReaders) {
        return InternalResult.map(
            tryParseOfficeXml(file, "word/footnotes.xml")
                .map(NotesXmlReader.footnote(bodyReaders.forName("footnotes"))::readElement)
                .orElse(InternalResult.success(list())),
            tryParseOfficeXml(file, "word/endnotes.xml")
                .map(NotesXmlReader.endnote(bodyReaders.forName("endnotes"))::readElement)
                .orElse(InternalResult.success(list())),
            Lists::eagerConcat).map(Notes::new);
    }

    private static Styles readStyles(Archive file) {
        return tryParseOfficeXml(file, "word/styles.xml")
            .map(StylesXml::readStylesXmlElement)
            .orElse(Styles.EMPTY);
    }

    private static Numbering readNumbering(Archive file) {
        return tryParseOfficeXml(file, "word/numbering.xml")
            .map(NumberingXml::readNumberingXmlElement)
            .orElse(Numbering.EMPTY);
    }

    private static ContentTypes readContentTypes(Archive file) {
        return tryParseOfficeXml(file, "[Content_Types].xml")
            .map(ContentTypesXml::readContentTypesXmlElement)
            .orElse(ContentTypes.DEFAULT);
    }

    private static Relationships readRelationshipsFor(Archive zipFile, String name) {
        return readRelationships(zipFile, "word/_rels/" + name + ".xml.rels");
    }

    private static Relationships readRelationships(Archive zipFile, String name) {
        return tryParseOfficeXml(zipFile, name)
            .map(RelationshipsXml::readRelationshipsXmlElement)
            .orElse(Relationships.EMPTY);
    }

    private static Optional<XmlElement> tryParseOfficeXml(Archive zipFile, String name) {
        return PassThroughException.wrap(() ->
            zipFile.tryGetInputStream(name).map(OfficeXml::parseXml));
    }

    private static XmlElement parseOfficeXml(Archive zipFile, String name) {
        return tryParseOfficeXml(zipFile, name)
            .orElseThrow(() -> new PassThroughException(new IOException("Missing entry in file: " + name)));
    }
}