// This file is part of Moonfire NVR, a security camera network video recorder.
// Copyright (C) 2020 The Moonfire NVR Authors
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// In addition, as a special exception, the copyright holders give
// permission to link the code of portions of this program with the
// OpenSSL library under certain conditions as described in each
// individual source file, and distribute linked combinations including
// the two.
//
// You must obey the GNU General Public License in all respects for all
// of the code used other than OpenSSL. If you modify file(s) with this
// exception, you may extend this exception to your version of the
// file(s), but you are not obligated to do so. If you do not wish to do
// so, delete this exception statement from your version. If you delete
// this exception statement from all source files in the program, then
// also delete it here.
//
// 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

use failure::Error;
use prettydiff::diff_slice;
use rusqlite::params;
use std::fmt::Write;

#[derive(Debug, PartialEq)]
struct Column {
    cid: u32,
    name: String,
    type_: String,
    notnull: bool,
    dflt_value: rusqlite::types::Value,
    pk: u32,
}

impl std::fmt::Display for Column {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{:?}", self)
    }
}

#[derive(Debug, Eq, PartialEq)]
struct Index {
    seq: u32,
    name: String,
    unique: bool,
    origin: String,
    partial: bool,
}

impl std::fmt::Display for Index {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{:?}", self)
    }
}

#[derive(Debug, Eq, PartialEq)]
struct IndexColumn {
    seqno: u32,
    cid: u32,
    name: String,
}

impl std::fmt::Display for IndexColumn {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{:?}", self)
    }
}

/// Returns a sorted vec of table names in the given connection.
fn get_tables(c: &rusqlite::Connection) -> Result<Vec<String>, rusqlite::Error> {
    c.prepare(r#"
        select
            name
        from
            sqlite_master
        where
            type = 'table' and
            name not like 'sqlite_%'
        order by name
    "#)?
     .query_map(params![], |r| r.get(0))?
     .collect()
}

/// Returns a vec of columns in the given table.
fn get_table_columns(c: &rusqlite::Connection, table: &str)
                     -> Result<Vec<Column>, rusqlite::Error> {
    // Note that placeholders aren't allowed for these pragmas. Just assume sane table names
    // (no escaping). "select * from pragma_..." syntax would be nicer but requires SQLite
    // 3.16.0 (2017-01-02). Ubuntu 16.04 Xenial (still used on Travis CI) has an older SQLite.
    c.prepare(&format!("pragma table_info(\"{}\")", table))?
     .query_map(params![], |r| Ok(Column {
         cid: r.get(0)?,
         name: r.get(1)?,
         type_: r.get(2)?,
         notnull: r.get(3)?,
         dflt_value: r.get(4)?,
         pk: r.get(5)?,
     }))?
     .collect()
}

/// Returns a vec of indices associated with the given table.
fn get_indices(c: &rusqlite::Connection, table: &str) -> Result<Vec<Index>, rusqlite::Error> {
    // See note at get_tables_columns about placeholders.
    c.prepare(&format!("pragma index_list(\"{}\")", table))?
     .query_map(params![], |r| Ok(Index {
         seq: r.get(0)?,
         name: r.get(1)?,
         unique: r.get(2)?,
         origin: r.get(3)?,
         partial: r.get(4)?,
     }))?
     .collect()
}

/// Returns a vec of all the columns in the given index.
fn get_index_columns(c: &rusqlite::Connection, index: &str)
                     -> Result<Vec<IndexColumn>, rusqlite::Error> {
    // See note at get_tables_columns about placeholders.
    c.prepare(&format!("pragma index_info(\"{}\")", index))?
     .query_map(params![], |r| Ok(IndexColumn {
         seqno: r.get(0)?,
         cid: r.get(1)?,
         name: r.get(2)?,
     }))?
     .collect()
}

pub fn get_diffs(n1: &str, c1: &rusqlite::Connection, n2: &str, c2: &rusqlite::Connection)
           -> Result<Option<String>, Error> {
    let mut diffs = String::new();

    // Compare table list.
    let tables1 = get_tables(c1)?;
    let tables2 = get_tables(c2)?;
    if tables1 != tables2 {
        write!(&mut diffs, "table list mismatch, {} vs {}:\n{}",
               n1, n2, diff_slice(&tables1, &tables2))?;
    }

    // Compare columns and indices for each table.
    for t in &tables1 {
        let columns1 = get_table_columns(c1, &t)?;
        let columns2 = get_table_columns(c2, &t)?;
        if columns1 != columns2 {
            write!(&mut diffs, "table {:?} column, {} vs {}:\n{}",
                   t, n1, n2, diff_slice(&columns1, &columns2))?;
        }

        let mut indices1 = get_indices(c1, &t)?;
        let mut indices2 = get_indices(c2, &t)?;
        indices1.sort_by(|a, b| a.name.cmp(&b.name));
        indices2.sort_by(|a, b| a.name.cmp(&b.name));
        if indices1 != indices2 {
            write!(&mut diffs, "table {:?} indices, {} vs {}:\n{}",
                   t, n1, n2, diff_slice(&indices1, &indices2))?;
        }

        for i in &indices1 {
            let ic1 = get_index_columns(c1, &i.name)?;
            let ic2 = get_index_columns(c2, &i.name)?;
            if ic1 != ic2 {
                write!(&mut diffs, "table {:?} index {:?} columns {} vs {}:\n{}",
                       t, i, n1, n2, diff_slice(&ic1, &ic2))?;
            }
        }
    }

    Ok(if diffs.is_empty() { None } else { Some(diffs) })
}