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use std::cmp::Ordering;
use anyhow::Result;
use crate::{encoding::d_decode_row, value::Value, Db};
use super::{
cell::fetch_cell,
encoding::{decode_page, Page},
};
#[derive(Debug)]
pub struct RangeEnd<T> {
pub inclusive: bool,
pub value: T,
}
#[derive(Debug)]
pub struct Range<T> {
pub backwards: bool,
pub prefix: Vec<T>,
pub start: Option<RangeEnd<T>>,
pub end: Option<RangeEnd<T>>,
}
impl Range<Value> {
fn while_f(&self, k: &[Value]) -> bool {
assert!(!self.backwards);
&self.prefix[..] == &k[0..self.prefix.len()]
&& self
.end
.as_ref()
.map(|end_end| {
if end_end.inclusive {
&k[self.prefix.len()] <= &end_end.value
} else {
&k[self.prefix.len()] < &end_end.value
}
})
.unwrap_or(true)
}
}
#[derive(Debug)]
pub struct RangeIterKV {
table: String,
tx_id: u64,
range: Range<Value>,
prev_key: Option<Vec<Value>>,
}
impl RangeIterKV {
pub fn new(range: Range<Value>, tx_id: u64, table: String) -> Self {
Self {
table,
tx_id,
range,
prev_key: None,
}
}
pub fn new_simple(table: String, tx_id: u64, key: Vec<Value>) -> Self {
Self {
table,
tx_id,
range: Range {
backwards: false,
prefix: key,
start: None,
end: None,
},
prev_key: None,
}
}
fn find_first(
&mut self,
db: &mut Db,
root_page: u64,
) -> Result<Option<(Vec<Value>, Vec<Value>)>> {
match decode_page(&db.get_page(root_page)?)? {
Page::BTreeLeaf(_tx_id, cells) => {
let mut id = 0;
let final_id = loop {
if id >= cells.len() {
return Ok(None);
}
let current_key = d_decode_row(&fetch_cell(db, &cells[id].0)?)?;
match current_key[0..self.range.prefix.len()].cmp(&self.range.prefix) {
Ordering::Less => {
id += 1;
continue;
}
Ordering::Equal => {
if let Some(start_end) = &self.range.start {
match current_key[self.range.prefix.len()].cmp(&start_end.value) {
Ordering::Less => {
id += 1;
continue;
}
Ordering::Equal => {
if start_end.inclusive {
break id;
} else {
id += 1;
continue;
}
}
Ordering::Greater => {
break id;
}
}
} else {
break id;
}
}
Ordering::Greater => {
return Ok(None);
}
}
};
let k = d_decode_row(&fetch_cell(db, &cells[final_id].0)?)?;
if self.range.while_f(&k) {
Ok(Some((
k,
d_decode_row(&fetch_cell(db, &cells[final_id].1)?)?,
)))
} else {
Ok(None)
}
}
Page::BTreeInterior(_tx_id, (left, cells)) => {
let mut id = 0;
let final_id = loop {
if id >= cells.len() {
if !cells.is_empty() {
break id;
} else {
return Ok(None);
}
}
let current_key = d_decode_row(&fetch_cell(db, &cells[id].0)?)?;
match current_key[0..self.range.prefix.len()].cmp(&self.range.prefix) {
Ordering::Less => {
id += 1;
continue;
}
Ordering::Equal => {
if let Some(start_end) = &self.range.start {
match current_key[self.range.prefix.len()].cmp(&start_end.value) {
Ordering::Less => {
id += 1;
continue;
}
Ordering::Equal => {
if start_end.inclusive {
break id;
} else {
id += 1;
continue;
}
}
Ordering::Greater => {
break id;
}
}
} else {
break id;
}
}
Ordering::Greater => {
break id;
}
}
};
self.find_first(
db,
if final_id == 0 {
left
} else {
cells[final_id - 1].1
},
)
}
_ => unreachable!(),
}
}
fn find_next(
&mut self,
db: &mut Db,
root_page: u64,
prev_key: Vec<Value>,
) -> Result<Option<(Vec<Value>, Vec<Value>)>> {
match decode_page(&db.get_page(root_page)?)? {
Page::BTreeLeaf(_tx_id, cells) => {
if cells.is_empty() {
return Ok(None);
}
let id = match cells.binary_search_by(|probe| {
let k = d_decode_row(&fetch_cell(db, &probe.0).unwrap()).unwrap();
k.cmp(&prev_key)
}) {
Ok(id) => id + 1,
Err(id) => id,
};
if id >= cells.len() {
return Ok(None);
}
let k = d_decode_row(&fetch_cell(db, &cells[id].0)?)?;
if self.range.while_f(&k) {
Ok(Some((k, d_decode_row(&fetch_cell(db, &cells[id].1)?)?)))
} else {
Ok(None)
}
}
Page::BTreeInterior(_tx_id, (left, cells)) => {
let id = match cells.binary_search_by(|probe| {
let k = d_decode_row(&fetch_cell(db, &probe.0).unwrap()).unwrap();
k.cmp(&prev_key)
}) {
Ok(id) => id + 1,
Err(id) => id,
};
if id > cells.len() {
return Ok(None);
}
self.find_next(db, if id == 0 { left } else { cells[id - 1].1 }, prev_key)
}
_ => unreachable!(),
}
}
pub fn next(&mut self, db: &mut Db) -> Result<Option<(Vec<Value>, Vec<Value>)>> {
let root_page = db.table_to_kv_id_or_error(self.tx_id, &self.table)?;
let res = if let Some(prev_key) = self.prev_key.take() {
self.find_next(db, root_page, prev_key)?
} else {
self.find_first(db, root_page)?
};
self.prev_key = res.as_ref().map(|(k, _)| k.clone());
Ok(res)
}
}