use std::{
    fs::{self, File},
    io::{Read, Write},
    path::PathBuf,
};

use flate2::{write::GzEncoder, Compression};
use index::{Checked, Settings};
use index_scheduler::TaskView;
use meilisearch_auth::Key;
use serde::Serialize;
use serde_json::{Map, Value};
use tempfile::TempDir;
use time::OffsetDateTime;
use uuid::Uuid;

use crate::{Metadata, Result, CURRENT_DUMP_VERSION};

pub struct DumpWriter {
    dir: TempDir,
}

impl DumpWriter {
    pub fn new(instance_uuid: Uuid) -> Result<DumpWriter> {
        let dir = TempDir::new()?;
        fs::write(
            dir.path().join("instance-uid"),
            &instance_uuid.as_hyphenated().to_string(),
        )?;

        let metadata = Metadata {
            dump_version: CURRENT_DUMP_VERSION,
            db_version: env!("CARGO_PKG_VERSION").to_string(),
            dump_date: OffsetDateTime::now_utc(),
        };
        fs::write(
            dir.path().join("metadata.json"),
            serde_json::to_string(&metadata)?,
        )?;

        std::fs::create_dir(&dir.path().join("indexes"))?;

        Ok(DumpWriter { dir })
    }

    pub fn create_index(&self, index_name: &str) -> Result<IndexWriter> {
        IndexWriter::new(self.dir.path().join("indexes").join(index_name))
    }

    pub fn create_keys(&self) -> Result<KeyWriter> {
        KeyWriter::new(self.dir.path().to_path_buf())
    }

    pub fn create_tasks_queue(&self) -> Result<TaskWriter> {
        TaskWriter::new(self.dir.path().join("tasks"))
    }

    pub fn persist_to(self, mut writer: impl Write) -> Result<()> {
        let gz_encoder = GzEncoder::new(&mut writer, Compression::default());
        let mut tar_encoder = tar::Builder::new(gz_encoder);
        tar_encoder.append_dir_all(".", self.dir.path())?;
        let gz_encoder = tar_encoder.into_inner()?;
        gz_encoder.finish()?;
        writer.flush()?;

        Ok(())
    }
}

pub struct KeyWriter {
    file: File,
}

impl KeyWriter {
    pub(crate) fn new(path: PathBuf) -> Result<Self> {
        let file = File::create(path.join("keys.jsonl"))?;
        Ok(KeyWriter { file })
    }

    pub fn push_key(&mut self, key: &Key) -> Result<()> {
        self.file.write_all(&serde_json::to_vec(key)?)?;
        self.file.write_all(b"\n")?;
        Ok(())
    }
}

pub struct TaskWriter {
    queue: File,
    update_files: PathBuf,
}

impl TaskWriter {
    pub(crate) fn new(path: PathBuf) -> Result<Self> {
        std::fs::create_dir(&path)?;

        let queue = File::create(path.join("queue.jsonl"))?;
        let update_files = path.join("update_files");
        std::fs::create_dir(&update_files)?;

        Ok(TaskWriter {
            queue,
            update_files,
        })
    }

    /// Pushes tasks in the dump.
    /// If the tasks has an associated `update_file` it'll use the `task_id` as its name.
    pub fn push_task(&mut self, task: &TaskView, update_file: Option<impl Read>) -> Result<()> {
        // TODO: this could be removed the day we implements `Deserialize` on the Duration.
        let mut task = task.clone();
        task.duration = None;

        self.queue.write_all(&serde_json::to_vec(&task)?)?;
        self.queue.write_all(b"\n")?;
        if let Some(mut update_file) = update_file {
            let mut file = File::create(&self.update_files.join(task.uid.to_string()))?;
            std::io::copy(&mut update_file, &mut file)?;
        }
        Ok(())
    }
}

pub struct IndexWriter {
    documents: File,
    settings: File,
}

impl IndexWriter {
    pub(crate) fn new(path: PathBuf) -> Result<Self> {
        std::fs::create_dir(&path)?;

        let documents = File::create(path.join("documents.jsonl"))?;
        let settings = File::create(path.join("settings.json"))?;

        Ok(IndexWriter {
            documents,
            settings,
        })
    }

    pub fn push_document(&mut self, document: &Map<String, Value>) -> Result<()> {
        self.documents.write_all(&serde_json::to_vec(document)?)?;
        self.documents.write_all(b"\n")?;
        Ok(())
    }

    pub fn settings(mut self, settings: &Settings<Checked>) -> Result<()> {
        self.settings.write_all(&serde_json::to_vec(&settings)?)?;
        Ok(())
    }
}

#[cfg(test)]
pub(crate) mod test {
    use std::{fmt::Write, io::BufReader, path::Path, str::FromStr};

    use flate2::bufread::GzDecoder;
    use index::Unchecked;

    use crate::test::{
        create_test_api_keys, create_test_documents, create_test_dump, create_test_instance_uid,
        create_test_settings, create_test_tasks,
    };

    use super::*;

    fn create_directory_hierarchy(dir: &Path) -> String {
        let mut ret = String::new();
        writeln!(ret, ".").unwrap();
        ret.push_str(&_create_directory_hierarchy(dir, 0));
        ret
    }

    fn _create_directory_hierarchy(dir: &Path, depth: usize) -> String {
        let mut ret = String::new();

        // the entries are not guarenteed to be returned in the same order thus we need to sort them.
        let mut entries = fs::read_dir(dir)
            .unwrap()
            .collect::<std::result::Result<Vec<_>, _>>()
            .unwrap();

        // I want the directories first and then sort by name.
        entries.sort_by(|a, b| {
            let (aft, bft) = (a.file_type().unwrap(), b.file_type().unwrap());

            if aft.is_dir() && bft.is_dir() {
                a.file_name().cmp(&b.file_name())
            } else if aft.is_file() {
                std::cmp::Ordering::Greater
            } else if bft.is_file() {
                std::cmp::Ordering::Less
            } else {
                a.file_name().cmp(&b.file_name())
            }
        });

        for (idx, entry) in entries.iter().enumerate() {
            let mut ident = String::new();

            for _ in 0..depth {
                ident.push_str(&"│");
                ident.push_str(&" ".repeat(4));
            }
            if idx == entries.len() - 1 {
                ident.push_str(&"└");
            } else {
                ident.push_str(&"├");
            }
            ident.push_str(&"-".repeat(4));

            let name = entry.file_name().into_string().unwrap();
            let file_type = entry.file_type().unwrap();
            let is_dir = file_type.is_dir().then_some("/").unwrap_or("");

            assert!(!file_type.is_symlink());
            writeln!(ret, "{ident} {name}{is_dir}").unwrap();

            if file_type.is_dir() {
                ret.push_str(&_create_directory_hierarchy(&entry.path(), depth + 1));
            }
        }
        ret
    }

    #[test]
    fn test_creating_dump() {
        let file = create_test_dump();
        let mut file = BufReader::new(file);

        // ============ ensuring we wrote everything in the correct place.
        let dump = tempfile::tempdir().unwrap();

        let gz = GzDecoder::new(&mut file);
        let mut tar = tar::Archive::new(gz);
        tar.unpack(dump.path()).unwrap();

        let dump_path = dump.path();

        // ==== checking global file hierarchy (we want to be sure there isn't too many files or too few)
        insta::assert_display_snapshot!(create_directory_hierarchy(dump_path), @r###"
        .
        ├---- indexes/
        │    └---- doggos/
        │    │    ├---- settings.json
        │    │    └---- documents.jsonl
        ├---- tasks/
        │    ├---- update_files/
        │    │    └---- 1
        │    └---- queue.jsonl
        ├---- keys.jsonl
        ├---- metadata.json
        └---- instance-uid
        "###);

        // ==== checking the top level infos
        let metadata = fs::read_to_string(dump_path.join("metadata.json")).unwrap();
        let metadata: Metadata = serde_json::from_str(&metadata).unwrap();
        insta::assert_json_snapshot!(metadata, { ".dumpDate" => "[date]" }, @r###"
        {
          "dumpVersion": "V6",
          "dbVersion": "0.29.0",
          "dumpDate": "[date]"
        }
        "###);

        let instance_uid = fs::read_to_string(dump_path.join("instance-uid")).unwrap();
        assert_eq!(
            Uuid::from_str(&instance_uid).unwrap(),
            create_test_instance_uid()
        );

        // ==== checking the index
        let docs = fs::read_to_string(dump_path.join("indexes/doggos/documents.jsonl")).unwrap();
        for (document, expected) in docs.lines().zip(create_test_documents()) {
            assert_eq!(
                serde_json::from_str::<Map<String, Value>>(document).unwrap(),
                expected
            );
        }
        let test_settings =
            fs::read_to_string(dump_path.join("indexes/doggos/settings.json")).unwrap();
        assert_eq!(
            serde_json::from_str::<Settings<Unchecked>>(&test_settings).unwrap(),
            create_test_settings().into_unchecked()
        );

        // ==== checking the task queue
        let tasks_queue = fs::read_to_string(dump_path.join("tasks/queue.jsonl")).unwrap();
        for (task, mut expected) in tasks_queue.lines().zip(create_test_tasks()) {
            // TODO: This can be removed once `Duration` from the `TaskView` is implemented.
            expected.0.duration = None;
            dbg!(&task);
            assert_eq!(serde_json::from_str::<TaskView>(task).unwrap(), expected.0);

            if let Some(expected_update) = expected.1 {
                let path = dump_path.join(format!("tasks/update_files/{}", expected.0.uid));
                println!("trying to open {}", path.display());
                let update = fs::read(path).unwrap();
                assert_eq!(update, expected_update);
            }
        }

        // ==== checking the keys
        let keys = fs::read_to_string(dump_path.join("keys.jsonl")).unwrap();
        for (key, expected) in keys.lines().zip(create_test_api_keys()) {
            assert_eq!(serde_json::from_str::<Key>(key).unwrap(), expected);
        }
    }
}