// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

//! # Storage layer for Notesmachine
//!
//! This library implements the core functionality of Notesmachine and
//! describes that functionality to a storage layer.  There's a bit of
//! intermingling in here which can't be helped, although it may make
//! sense in the future to separate the decomposition of the note
//! content into a higher layer.
//!
//! Notesmachine storage notes consist of two items: Note and Kasten.
//! This distinction is somewhat arbitrary, as structurally these two
//! items are stored in the same table.
//!
//! - Boxes have titles (and date metadata)
//! - Notes have content and a type (and date metadata)
//! - Notes are stored in boxes
//!   - Notes are positioned with respect to other notes.
//!   - There are two positions:
//!     - Siblings, creating lists
//!     - Children, creating trees like this one
//! - Notes may have references (pointers) to other boxes
//! - Notes may be moved around
//! - Notes may be deleted
//! - Boxes may be deleted
//! - When a box is renamed, every reference to that box is auto-edited to
//!   reflect the change. If a box is renamed to match an existing box, the
//!   notes in both boxes are merged.
//!   
//! Note-to-note relationships form trees, and are kept in a SQL database of
//! (`parent_id`, `child_id`, `position`, `relationship_type`). The
//! `position` is a monotonic index on the parent (that is, every pair
//! (`parent_id`, `position`) must be unique).  The `relationship_type` is
//! an enum and can specify that the relationship is *original*,
//! *embedding*, or *referencing*.  An embedded or referenced note may be
//! read/write or read-only with respect to the original, but there is only
//! one original note at any time.
//!
//! Note-to-box relationships form a graph, and are kept in the SQL database
//! as a collection of *edges* from the note to the box (and naturally
//! vice-versa).
//!
//! - Decision: When an original note is deleted, do all references and
//!   embeddings also get deleted, or is the oldest one elevated to be a new
//!   "original"?  Or is that something the user may choose?
//!
//! - Decision: Should the merging issue be handled at this layer, or would
//!   it make sense to move this to a higher layer, and only provide the
//!   hooks for it here?
//!

use crate::errors::NoteStoreError;
use crate::reference_parser::build_references;
use crate::store_private::*;
use crate::structs::*;
use sqlx::sqlite::SqlitePool;
use std::cmp;
// use std::collections::HashMap;
use std::sync::Arc;

/// A handle to our Sqlite database.
#[derive(Clone, Debug)]
pub struct NoteStore(Arc<SqlitePool>);

type NoteResult<T> = core::result::Result<T, NoteStoreError>;

// After wrestling for a while with the fact that 'box' is a reserved
// word in Rust, I decided to just go with Note (note) and Kasten
// (box).

impl NoteStore {
    /// Initializes a new instance of the note store.  Note that the
    /// note store holds an Arc internally; this code is (I think)
    /// safe to Send.
    pub async fn new(url: &str) -> NoteResult<Self> {
        let pool = SqlitePool::connect(url).await?;
        Ok(NoteStore(Arc::new(pool)))
    }
    /// Erase all the data in the database and restore it
    /// to its original empty form.  Do not use unless you
    /// really, really want that to happen.
    pub async fn reset_database(&self) -> NoteResult<()> {
        reset_database(&*self.0).await.map_err(NoteStoreError::DBError)
    }

    /// Fetch page by slug
    ///
    /// Supports the use case of the user navigating to a known place
    /// via a bookmark or other URL.  Since the title isn't clear from
    /// the slug, the slug is insufficient to generate a new page, so
    /// this use case says that in the event of a failure to find the
    /// requested page, return a basic NotFound.
    pub async fn get_kasten_by_slug(&self, slug: &str) -> NoteResult<Vec<Note>> {
        let maybekasten = select_kasten_by_slug(&*self.0, slug).await;
        match maybekasten {
            Ok(v) => Ok(v),
            Err(sqlx::Error::RowNotFound) => Err(NoteStoreError::NotFound),
            Err(_) => maybekasten.map_err(NoteStoreError::DBError),
        }
    }

    pub async fn get_kasten_by_title(&self, title: &str) -> NoteResult<Vec<Note>> {
        if title.len() == 0 {
            return Err(NoteStoreError::NotFound);
        }

        let kasten = select_kasten_by_title(&*self.0, title).await?;
        if kasten.len() > 0 {
            return Ok(kasten);
        }

        let references = build_references(&title);
        if references.len() > 0 {
            return Err(NoteStoreError::InvalidNoteStructure(
                "Titles may not contain nested references.".to_string(),
            ));
        }

        let mut tx = self.0.begin().await?;
        let slug = generate_slug(&mut tx, title).await?;
        let zettlekasten = create_zettlekasten(&title, &slug);
        let _ = insert_note(&mut tx, &zettlekasten).await?;
        tx.commit().await?;

        Ok(vec![Note::from(zettlekasten)])
    }

    pub async fn add_note(&self, note: &NewNote, parent_id: &str, location: i64) -> NoteResult<String> {
        self.insert_note(note, &ParentId(parent_id.to_string()), location, RelationshipKind::Direct).await
    }

    /// Move a note from one location to another.
    pub async fn move_note(
        &self,
        note_id: &str,
        old_parent_id: &str,
        new_parent_id: &str,
        new_location: i64,
    ) -> NoteResult<()> {
        let mut tx = self.0.begin().await?;

		let old_parent_id = ParentId(old_parent_id.to_string());
		let new_parent_id = ParentId(new_parent_id.to_string());
		let note_id = NoteId(note_id.to_string());
		
        let old_note = select_note_to_note_relationship(&mut tx, &old_parent_id, &note_id).await?;
        let old_note_location = old_note.location;
        let old_note_kind = old_note.kind;

        let _ = delete_note_to_note_relationship(&mut tx, &old_parent_id, &note_id).await?;
        let _ = close_hole_for_deleted_note(&mut tx, &old_parent_id, old_note_location).await?;
        let parent_max_location = assert_max_child_location_for_note(&mut tx, &new_parent_id).await?;
        let new_location = cmp::min(parent_max_location + 1, new_location);
        let _ = make_room_for_new_note(&mut tx, &new_parent_id, new_location).await?;
        let _ =
            insert_note_to_note_relationship(&mut tx, &new_parent_id, &note_id, new_location, &old_note_kind).await?;
        tx.commit().await?;
        Ok(())
    }

    /// Deletes a note.  If the note's relationship drops to zero, all
    /// references from that note to pages are also deleted.
    pub async fn delete_note(&self, note_id: &str, note_parent_id: &str) -> NoteResult<()> {
        let mut tx = self.0.begin().await?;
		let note_id = NoteId(note_id.to_string());
		let parent_id = ParentId(note_parent_id.to_string());
		
		let _ = delete_note_to_note_relationship(&mut tx, &parent_id, &note_id);
		// The big one: if zero parents report having an interest in this note, then it,
		// *and any sub-relationships*, go away.
        if count_existing_note_relationships(&mut tx, &note_id).await? == 0 {
            let _ = delete_note_to_kasten_relationships(&mut tx, &note_id).await?;
            let _ = delete_note(&mut tx, &note_id).await?;
        }
        tx.commit().await?;
        Ok(())
    }

    /// Updates a note's content.  Completely rebuilds the note's
    /// outgoing edge reference list every time.
    pub async fn update_note_content(&self, note_id: &str, content: &str) -> NoteResult<()> {
        let references = build_references(&content);
		let note_id = NoteId(note_id.to_string());

        let mut tx = self.0.begin().await?;
        let _ = update_note_content(&mut tx, &note_id, &content).await?;
        let found_references = find_all_kasten_references_for(&mut tx, &references).await?;
        let new_references = diff_references(&references, &found_references);
        let mut known_reference_ids: Vec<NoteId> = Vec::new();
        for one_reference in new_references.iter() {
            let slug = generate_slug(&mut tx, one_reference).await?;
            let zettlekasten = create_zettlekasten(&one_reference, &slug);
            let _ = insert_note(&mut tx, &zettlekasten).await?;
            known_reference_ids.push(NoteId(slug));
        }

        known_reference_ids.append(&mut found_references.iter().map(|r| NoteId(r.id.clone())).collect());
        let _ = insert_bulk_note_to_kasten_relationships(&mut tx, &note_id, &known_reference_ids).await?;
        tx.commit().await?;
        Ok(())
    }
	
	
}

// The Private stuff

impl NoteStore {
    // Pretty much the most dangerous function in our system. Has to
    // have ALL the error checking.
    async fn insert_note(&self, note: &NewNote, parent_id: &ParentId, location: i64, kind: RelationshipKind) -> NoteResult<String> {
        if location < 0 {
            return Err(NoteStoreError::InvalidNoteStructure(
                "Add note: A negative position is not valid.".to_string(),
            ));
        }

        if parent_id.is_empty() {
            return Err(NoteStoreError::InvalidNoteStructure(
                "Add note: A parent note ID is required.".to_string(),
            ));
        }

        if note.id.is_empty() {
            return Err(NoteStoreError::InvalidNoteStructure(
                "Add note: Your note should have an id already".to_string(),
            ));
        }

        if note.content.is_empty() {
            return Err(NoteStoreError::InvalidNoteStructure(
                "Add note: Empty notes are not supported.".to_string(),
            ));
        }

        let references = build_references(&note.content);

        let mut tx = self.0.begin().await?;
        let location = cmp::min(
            assert_max_child_location_for_note(&mut tx, parent_id).await? + 1,
            location,
        );

		let note_id = NoteId(note.id.clone());
        insert_note(&mut tx, &note).await?;
        make_room_for_new_note(&mut tx, &parent_id, location).await?;
        insert_note_to_note_relationship(&mut tx, &parent_id, &note_id, location, &kind).await?;

        let found_references = find_all_kasten_references_for(&mut tx, &references).await?;
        let new_references = diff_references(&references, &found_references);
        let mut known_reference_ids: Vec<NoteId> = Vec::new();
        for one_reference in new_references.iter() {
            let slug = generate_slug(&mut tx, one_reference).await?;
            let zettlekasten = create_zettlekasten(&one_reference, &slug);
            let _ = insert_note(&mut tx, &zettlekasten).await?;
            known_reference_ids.push(NoteId(slug));
        }

        known_reference_ids.append(&mut found_references.iter().map(|r| NoteId(r.id.clone())).collect());
        let _ = insert_bulk_note_to_kasten_relationships(&mut tx, &note_id, &known_reference_ids).await?;
        tx.commit().await?;
        Ok(note_id.to_string())
    }
}