package gitlet;

import java.io.File;
import java.io.Serial;
import java.io.Serializable;
import java.time.Instant;
import java.util.*;

import static gitlet.Utils.*;


/**
 * Represents a gitlet commit object.
 *
 * @author Abraham Briones
 */
public class Commit implements Serializable {

    /**
     * Serial ID so Java can serialize and deserialize.
     */
    @Serial
    private static final long serialVersionUID = 1234567L;

    /**
     * The message of this Commit.
     */
    private final String message;

    /**
     * The date and time when the commit object was made
     */
    private final Instant datetime;

    /**
     * The files that this commit will track.
     * It is composed of FileName(String):Blob (Key:value) pairings.
     */
    private final TreeMap<String, Blob> commitFiles;

    /**
     * The SHA-1 representation of the current commit.
     */
    private final String commitID;

    /**
     * The SHA-1 representation of the parent commit
     */
    private final String parentCommit;

    /**
     * The name of the branch that this commit belongs to.
     */
    private final String branch;


    /**
     * The constructor used when initializing a repository. It record EPOC time and a predefined
     * commit message. It does not track any files nor does it have a parent commit.
     */
    public Commit() {
        this.message = "initial commit";
        this.datetime = Instant.EPOCH;
        this.commitFiles = null;
        this.parentCommit = null;
        this.commitID = this.setSHA();
        this.branch = "master";
    }

    /**
     * A second constructor used for all other commits after the initial commit.
     *
     * @param message      the message encoded into the commit
     * @param commitFiles  a map of files that this commit should track
     * @param parentCommit the SHA-1 hash of the parent commit
     * @param branch       the name of the branch this commit belongs to
     */
    public Commit(String message, TreeMap<String, Blob> commitFiles, String parentCommit, String branch) {
        this.message = message;
        this.datetime = Instant.now();
        this.commitFiles = commitFiles;
        this.parentCommit = parentCommit;
        this.commitID = this.setSHA();
        this.branch = branch;
    }

    /**
     * Contstructor to make a copy of a commit.
     */
    public Commit(Commit copyCommit) {
        this.message = copyCommit.message;
        this.datetime = Instant.now();
        this.commitFiles = copyCommit.commitFiles;
        this.parentCommit = copyCommit.parentCommit;
        this.commitID = copyCommit.commitID;
        this.branch = copyCommit.branch;
    }

    /**
     * Retrieve the date and time when this commit object was made.
     *
     * @return datetime string
     */
    public String getDateTime() {
        return this.datetime.toString();
    }

    public String getCommitID() {
        return this.commitID;
    }

    public String getMessage() {
        return this.message;
    }

    public String getBranch() {
        return this.branch;
    }

    /**
     * Get parent commit SHa
     */
    public String getParentCommit() {
        return this.parentCommit;
    }

    public TreeMap<String, Blob> getCommitFiles() {
        return this.commitFiles;
    }

    /**
     * Set and return the SHA-1 of the commit object.
     * The SHA-1 is composed of the metadata as well as the string representation
     * of the blob objects the commit object tracks.
     */
    private String setSHA() {
        String commitContents = this.message + this.getDateTime() + this.parentCommit + this.branch;
        StringBuilder fileContentsString = new StringBuilder();
        if (this.parentCommit != null) {
            for (Blob b : commitFiles.values()) {
                fileContentsString.append(b.toString());
            }
        }

        commitContents += fileContentsString;
        return Utils.sha1(commitContents);
    }


    public void saveCommit() {
        File commitFile = join(Repository.OBJECT_DIR, this.commitID);
        Utils.writeObject(commitFile, this);

    }


    /*
     * Override this method in your custom class
     * used as key or value in the LinkedHashMap
     */
    @Override
    public String toString() {
        String files = this.commitFiles == null
                ? "EMPTY FILES"
                : this.getCommitFiles().toString();


        return String.format("Commit: %s\nCommit message: %s\nParent commit: %s\nFiles tracking:\n%s\nBranch:%s\n", this.getCommitID(),
                this.message, this.getParentCommit(), files, this.getBranch());

    }


}