//  Stiletto
//  Copyright (C) 2020 Stiletto Authors
//
//  This program is free software: you can redistribute it and/or modify
//  it under the terms of the GNU Affero General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU Affero General Public License for more details.
//
//  You should have received a copy of the GNU Affero General Public License
//  along with this program.  If not, see <https://www.gnu.org/licenses/>.

use crate::{DocumentSnapshot, STILETTO_FORMAT_MAJOR, STILETTO_FORMAT_MINOR};

use std::error::Error;
use std::fmt;
use std::fs::File;
use std::io;
use std::path::PathBuf;

#[derive(Debug)]
pub enum MigrationError {
    SerdeJsonError(serde_json::Error),
    SerdeBareError(serde_bare::Error),
    IoError(io::Error),

    UnexpectedVersion(u16, u16, u16, u16),
}

#[derive(Debug)]
pub enum StilettoDocument {
    DocumentSnapshot0_1(DocumentSnapshot),
    DocumentSnapshot0_2(DocumentSnapshot),
}

impl StilettoDocument {
    pub fn version(&self) -> (u16, u16) {
        match &self {
            StilettoDocument::DocumentSnapshot0_1(_) => (0, 1),
            StilettoDocument::DocumentSnapshot0_2(_) => (0, 2),
        }
    }

    pub fn migrate_to_next(self) -> StilettoDocument {
        match self {
            StilettoDocument::DocumentSnapshot0_1(snapshot) =>  StilettoDocument::DocumentSnapshot0_2(snapshot) ,
            StilettoDocument::DocumentSnapshot0_2(_) => self,
        }
    }

    pub fn migrate_to_latest(mut self) -> DocumentSnapshot {
        while self.version() != (STILETTO_FORMAT_MAJOR, STILETTO_FORMAT_MINOR) {
            self = self.migrate_to_next()
        }

        assert!(matches!(self, StilettoDocument::DocumentSnapshot0_2(_)));
        match self {
            StilettoDocument::DocumentSnapshot0_2(snapshot) => snapshot,
            _ => panic!("Wrong Document Snapshot Version")
        }
    }
}


impl fmt::Display for MigrationError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match &self {
            MigrationError::SerdeJsonError(e) => e.fmt(f),
            MigrationError::SerdeBareError(e) => e.fmt(f),
            MigrationError::IoError(e) => e.fmt(f),
            MigrationError::UnexpectedVersion(major, minor, e_major, e_minor) => {
                write!(
                    f, "Unexpected version ({}, {}): was expecting ({}, {})",
                    major, minor, e_major, e_minor
                )
            },
        }
    }
}

impl Error for MigrationError {
    fn source(&self) -> Option<&(dyn Error + 'static)> {
        match self {
            MigrationError::SerdeJsonError(e) => e.source(),
            MigrationError::SerdeBareError(e) => e.source(),
            MigrationError::IoError(e) => e.source(),
            MigrationError::UnexpectedVersion(..) => None,
        }
    }
}

impl From<io::Error> for MigrationError {
    fn from(error: io::Error) -> Self {
        MigrationError::IoError(error)
    }
}

impl From<serde_json::Error> for MigrationError {
    fn from(error: serde_json::Error) -> Self {
        MigrationError::SerdeJsonError(error)
    }
}

impl From<serde_bare::Error> for MigrationError {
    fn from(error: serde_bare::Error) -> Self {
        MigrationError::SerdeBareError(error)
    }
}

fn open_0_1(path: &PathBuf) -> Result<StilettoDocument, MigrationError> {
    let f = File::open(path)?;
    let document_snapshot: DocumentSnapshot = serde_json::from_reader(f)?;
    if document_snapshot.format_version_major != 0 ||
        document_snapshot.format_version_minor != 1 {
        Err(MigrationError::UnexpectedVersion(
            document_snapshot.format_version_major,
            document_snapshot.format_version_minor,
            0, 1
        ))
    } else {
        Ok(StilettoDocument::DocumentSnapshot0_1(document_snapshot))
    }
}

fn open_0_2(path: &PathBuf) -> Result<StilettoDocument, MigrationError> {
    let f = File::open(path)?;
    let document_snapshot: DocumentSnapshot = serde_bare::from_reader(f)?;
    Ok(StilettoDocument::DocumentSnapshot0_2(document_snapshot))
}

pub fn open_stiletto_document(path: &PathBuf) -> Result<StilettoDocument, MigrationError> {
    if let Ok(res) = open_0_1(path) {
        return Ok(res);
    }

    open_0_2(path)
}