// Back - An extremely simple git issue tracking system. Inspired by tvix's
// panettone
//
// Copyright (C) 2024 Benedikt Peetz <benedikt.peetz@b-peetz.de>
// SPDX-License-Identifier: AGPL-3.0-or-later
//
// This file is part of Back.
//
// You should have received a copy of the License along with this program.
// If not, see <https://www.gnu.org/licenses/agpl.txt>.

use std::fmt::Display;

use chrono::DateTime;
use gix::{bstr::ByteSlice, Commit, Id, ObjectId, Repository};
use raw::{Operation, RawIssue};
use rocket::response::content::RawHtml;

use super::format::{BackString, Markdown};

mod raw;

#[derive(Debug, Default)]
pub struct TimeStamp {
    value: u64,
}
impl TimeStamp {
    pub fn new(val: u64) -> Self {
        Self { value: val }
    }
}
impl Display for TimeStamp {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let date =
            DateTime::from_timestamp(self.value as i64, 0).expect("This timestamp should be vaild");

        let newdate = date.format("%Y-%m-%d %H:%M:%S");
        f.write_str(newdate.to_string().as_str())
    }
}

#[derive(Debug)]
pub struct Comment<'a> {
    pub id: Id<'a>,
    pub author: Author,
    pub message: Markdown,
    pub timestamp: TimeStamp,
}

#[derive(Debug, Default)]
pub struct Author {
    name: BackString,
    email: BackString,
}

#[derive(Debug)]
pub struct IssueId<'a> {
    value: Id<'a>,
}
impl<'a> IssueId<'a> {
    pub fn new(id: Id<'a>) -> Self {
        Self { value: id }
    }
}
impl Display for IssueId<'_> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let shortend = self.value.shorten().expect("This should work.");
        f.write_str(shortend.to_string().as_str())
    }
}

#[derive(Default, Debug, PartialEq, Eq, PartialOrd, Ord, Copy, Clone)]
pub enum Status {
    #[default]
    Open,
    Closed,
}
impl Display for Status {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Status::Open => f.write_str("Open"),
            Status::Closed => f.write_str("Closed"),
        }
    }
}

#[derive(Debug)]
pub struct Issue<'a> {
    pub id: IssueId<'a>,
    pub author: Author,
    pub timestamp: TimeStamp,
    pub title: Markdown,
    pub message: Markdown,
    pub comments: Vec<Comment<'a>>,
    pub status: Status,
    pub last_status_change: Option<TimeStamp>,
}
impl<'a> Issue<'a> {
    pub fn default_with_id(id: Id<'a>) -> Self {
        Self {
            id: IssueId::new(id),
            author: Author::default(),
            timestamp: TimeStamp::default(),
            title: Markdown::default(),
            message: Markdown::default(),
            comments: <Vec<Comment>>::default(),
            status: Status::default(),
            last_status_change: <Option<TimeStamp>>::default(),
        }
    }

    pub fn from_commit_id(repo: &'a Repository, commit_id: ObjectId) -> Self {
        fn unwrap_id<'b>(repo: &Repository, id: &Commit<'b>) -> (RawIssue, Id<'b>) {
            let tree_obj = repo
                .find_object(id.tree_id().unwrap())
                .expect("The object with this id should exist.")
                .try_into_tree()
                .expect("The git-bug's data model enforces this.");

            let ops_ref = tree_obj.find_entry("ops").unwrap();

            let issue_data = repo
                .find_object(ops_ref.object_id())
                .expect("The object with this id should exist.")
                .try_into_blob()
                .expect("The git-bug's data model enforces this.")
                .data
                .clone();

            let raw_issue = serde_json::from_str(
                issue_data
                    .to_str()
                    .expect("git-bug's ensures, that this is valid json."),
            )
            .expect("The returned json should be valid");

            (raw_issue, id.id())
        }

        let commit_obj = repo
            .find_object(commit_id)
            .expect("The object with this id should exist.")
            .try_into_commit()
            .expect("The git-bug's data model enforces this.");

        let mut issues = vec![unwrap_id(repo, &commit_obj)];

        let mut current_commit_obj = commit_obj;
        while current_commit_obj.parent_ids().count() != 0 {
            assert_eq!(
                current_commit_obj.parent_ids().count(),
                1,
                "There should be only one parent"
            );
            let parent = current_commit_obj
                .parent_ids()
                .last()
                .expect("One does exist");

            let parent_id = parent.object().expect("The object exists").id;
            let parent_commit = repo
                .find_object(parent_id)
                .expect("This is a valid id")
                .try_into_commit()
                .expect("This should be a commit");

            issues.push(unwrap_id(repo, &parent_commit));
            current_commit_obj = parent_commit;
        }

        let mut final_issue = Self::default_with_id(current_commit_obj.id());
        for (issue, id) in issues {
            for op in issue.operations {
                match op {
                    Operation::AddComment { timestamp, message } => {
                        final_issue.comments.push(Comment {
                            id,
                            author: issue.author.load_identity(repo),
                            message: Markdown::from(message),
                            timestamp: TimeStamp::new(timestamp),
                        })
                    }
                    Operation::Create {
                        timestamp,
                        title,
                        message,
                    } => {
                        final_issue.author = issue.author.load_identity(repo);
                        final_issue.title = Markdown::from(title);
                        final_issue.message = Markdown::from(message);
                        final_issue.timestamp = TimeStamp::new(timestamp);
                    }
                    Operation::SetStatus { timestamp, status } => {
                        final_issue.status = status;
                        final_issue.last_status_change = Some(TimeStamp::new(timestamp));
                    }
                }
            }
        }
        final_issue
    }

    pub fn to_list_entry(&self) -> RawHtml<String> {
        let comment_list = if self.comments.is_empty() {
            String::new()
        } else {
            format!(
                r#"
                <span class="comment-count"> - {} comments</span>
            "#,
                self.comments.len()
            )
        };
        let Issue {
            id,
            title,
            message: _,
            author,
            timestamp,
            comments: _,
            status: _,
            last_status_change: _,
        } = self;
        let Author { name, email } = author;
        RawHtml(format!(
            r#"
               <li>
                  <a href="/issue/{id}">
                     <p>
                        <span class="issue-subject">{title}</span>
                     </p>
                     <span class="issue-number">{id}</span> - <span class="created-by-at">Opened by <span class="user-name">{name}</span> <span class="user-email">&lt;{email}&gt;</span> at <span class="timestamp">{timestamp}</span></span>{comment_list}                  </a>
               </li>
"#,
        ))
    }

    pub fn to_html(&self) -> RawHtml<String> {
        let fmt_comments: String = self
            .comments
            .iter()
            .map(|val| {
                let Comment {
                    id,
                    author,
                    message,
                    timestamp,
                } = val;
                let Author { name, email: _ } = author;

                format!(
                    r#"
               <li class="comment" id="{id}">
                  {message}
                  <p class="comment-info"><span class="user-name">{name} at {timestamp}</span></p>
               </li>
                "#,
                )
            })
            .collect::<Vec<String>>()
            .join("\n");

        let maybe_comments = if fmt_comments.is_empty() {
            String::new()
        } else {
            format!(
                r#"
            <ol class="issue-history">
            {fmt_comments}
            </ol>
            "#
            )
        };

        {
            let Issue {
                id,
                title,
                message,
                author,
                timestamp,
                comments: _,
                status: _,
                last_status_change: _,
            } = self;
            let Author { name, email } = author;
            let html_title = BackString::from(title.clone());

            RawHtml(format!(
                r#"
<!DOCTYPE html>
<html lang="en">
   <head>
      <title>{html_title} | Back</title>
      <link href="/style.css" rel="stylesheet" type="text/css">
      <meta content="width=device-width,initial-scale=1" name="viewport">
   </head>
   <body>
      <div class="content">
         <nav>
         <a href="/issues/open">Open Issues</a>
         <a href="/issues/closed">Closed Issues</a>
         </nav>
         <header>
            <h1>{title}</h1>
            <div class="issue-number">{id}</div>
         </header>
         <main>
            <div class="issue-info">
                <span class="created-by-at">Opened by <span class="user-name">{name}</span> <span class="user-email">&lt;{email}&gt;</span> at <span class="timestamp">{timestamp}</span></span>
            </div>
            {message}
            {maybe_comments}
         </main>
         <footer>
            <nav>
            <a href="/issues/open">Open Issues</a>
            <a href="/issues/closed">Closed Issues</a>
            </nav>
         </footer>
      </div>
   </body>
</html>
"#,
            ))
        }
    }
}