ironwork-rt 0.1.2

//! Recordings: each call a run made and the answer it got, as text a person can read and edit.
//! [`Replay`] answers from a recording; [`Recorder`] writes one while another backend answers.
//!
//! ```text
//! # ironwork sql recording 1
//! @ 1 PAYROLL:3:9f2a41c0 SELECT
//! > char:"00123"
//! < 0 00000 rows=1
//! = dec:1234.50 | char:"SMITH" | null
//! ```

use super::{Abandoned, Answer, Call, Database, Outcome, Value};
use std::io::Write;
use super::fingerprint;

const HEADER: &str = "# ironwork sql recording 1";

#[derive(Debug)]
struct Entry {
    program: String,
    ordinal: u32,
    hash: u32,
    verb: String,
    cursor: Option<String>,
    inputs: Vec<Value>,
    outcome: Outcome,
}

impl Entry {
    fn answers(&self, call: &Call) -> bool {
        self.program == call.program
            && self.ordinal == call.ordinal
            && self.hash == fingerprint(call.text)
            && self.verb == call.verb
            && self.cursor.as_deref() == call.cursor
            && self.inputs == call.inputs
    }
}

fn describe(program: &str, ordinal: u32, hash: u32, verb: &str, cursor: Option<&str>, inputs: &[Value]) -> String {
    let cursor = cursor.map(|c| format!(" {c}")).unwrap_or_default();
    let inputs = if inputs.is_empty() { String::new() } else { format!(" with {}", values_text(inputs)) };
    format!("{program}:{ordinal}:{hash:08x} {verb}{cursor}{inputs}")
}

/// Answers calls from a recording. Strict replay answers call n from entry n; keyed replay answers
/// each call from the first unused entry with the same statement and inputs. A call the recording
/// does not hold ends the run.
pub struct Replay {
    entries: Vec<Entry>,
    used: Vec<bool>,
    next: usize,
    keyed: bool,
}

impl Replay {
    pub fn parse(text: &str, keyed: bool) -> Result<Self, String> {
        let mut entries: Vec<Entry> = Vec::new();
        let mut header = false;
        let mut awaiting_outcome = false;
        for (n, line) in text.lines().enumerate().map(|(i, l)| (i + 1, l.trim_end())) {
            let fail = |why: String| format!("line {n}: {why}");
            if line.is_empty() {
                continue;
            }
            if line.starts_with('#') {
                header |= line == HEADER;
                continue;
            }
            if !header {
                return Err(fail(format!("a recording starts with \"{HEADER}\"")));
            }
            let (mark, rest) = line.split_at(1);
            let rest = rest.trim_start();
            match mark {
                "@" => {
                    if awaiting_outcome {
                        return Err(fail("the call before this one has no < line".into()));
                    }
                    let words: Vec<&str> = rest.split_whitespace().collect();
                    let [_, id, verb, cursor @ ..] = words.as_slice() else { return Err(fail("@ takes a number, PROGRAM:ORDINAL:HASH and a verb".into())) };
                    let parts: Vec<&str> = id.split(':').collect();
                    let [program, ordinal, hash] = parts.as_slice() else { return Err(fail(format!("{id} is not PROGRAM:ORDINAL:HASH"))) };
                    let ordinal = ordinal.parse().map_err(|_| fail(format!("{ordinal} is not an ordinal")))?;
                    let hash = u32::from_str_radix(hash, 16).map_err(|_| fail(format!("{hash} is not a hexadecimal hash")))?;
                    let cursor = match cursor {
                        [] => None,
                        [c] => Some((*c).to_owned()),
                        _ => return Err(fail("@ takes at most one cursor after the verb".into())),
                    };
                    entries.push(Entry { program: (*program).into(), ordinal, hash, verb: (*verb).into(), cursor, inputs: Vec::new(), outcome: Outcome::ok() });
                    awaiting_outcome = true;
                }
                ">" => match entries.last_mut() {
                    Some(e) if awaiting_outcome && e.inputs.is_empty() => e.inputs = parse_values(rest).map_err(fail)?,
                    _ => return Err(fail("a > line belongs after an @ line, before its < line".into())),
                },
                "<" => match entries.last_mut() {
                    Some(e) if awaiting_outcome => {
                        e.outcome = parse_outcome(rest).map_err(fail)?;
                        awaiting_outcome = false;
                    }
                    _ => return Err(fail("a < line belongs after an @ line".into())),
                },
                "=" => match entries.last_mut() {
                    Some(e) if !awaiting_outcome => e.outcome.rows.push(parse_values(rest).map_err(fail)?),
                    _ => return Err(fail("an = line belongs after a < line".into())),
                },
                _ => return Err(fail(format!("{mark} starts no kind of line"))),
            }
        }
        if awaiting_outcome {
            return Err("the last call has no < line".into());
        }
        if !header {
            return Err(format!("a recording starts with \"{HEADER}\""));
        }
        let used = vec![false; entries.len()];
        Ok(Self { entries, used, next: 0, keyed })
    }

    fn answer(&mut self, call: &Call) -> Answer {
        let found = if self.keyed {
            (0..self.entries.len()).find(|&i| !self.used[i] && self.entries[i].answers(call))
        } else {
            (self.next < self.entries.len() && self.entries[self.next].answers(call)).then_some(self.next)
        };
        let actual = describe(call.program, call.ordinal, fingerprint(call.text), call.verb, call.cursor, call.inputs);
        let Some(i) = found else {
            let expected = match self.entries.get(self.next).filter(|_| !self.keyed) {
                Some(e) => format!("the recording's call {} is {}", self.next + 1, describe(&e.program, e.ordinal, e.hash, &e.verb, e.cursor.as_deref(), &e.inputs)),
                None => "the recording holds no such call".into(),
            };
            return Err(Abandoned { code: "SQLR", message: format!("{expected}, and the run made {actual}") });
        };
        self.used[i] = true;
        self.next = i + 1;
        Ok(self.entries[i].outcome.clone())
    }
}

impl Database for Replay {
    fn execute(&mut self, call: &Call) -> Answer {
        self.answer(call)
    }
    fn open(&mut self, call: &Call) -> Answer {
        self.answer(call)
    }
    fn fetch(&mut self, call: &Call) -> Answer {
        self.answer(call)
    }
    fn close(&mut self, call: &Call) -> Answer {
        self.answer(call)
    }
    fn commit(&mut self, call: &Call) -> Answer {
        self.answer(call)
    }
    fn rollback(&mut self, call: &Call) -> Answer {
        self.answer(call)
    }
}

/// Writes every call and its answer while `inner` answers.
pub struct Recorder<'w> {
    inner: Box<dyn Database + 'w>,
    out: Box<dyn Write + 'w>,
    seq: u64,
}

impl<'w> Recorder<'w> {
    /// `source` names what answered, and goes in the recording's header.
    pub fn new(inner: Box<dyn Database + 'w>, mut out: Box<dyn Write + 'w>, source: &str) -> std::io::Result<Self> {
        writeln!(out, "{HEADER}\n# source: {source}")?;
        Ok(Self { inner, out, seq: 0 })
    }

    fn record(&mut self, call: &Call, answer: Answer) -> Answer {
        let outcome = answer?;
        self.seq += 1;
        let text = entry_text(self.seq, call, &outcome);
        // Flushed per call: a served session ends when the server is interrupted, not by returning.
        self.out.write_all(text.as_bytes()).and_then(|()| self.out.flush()).map_err(|e| Abandoned { code: "SQLR", message: format!("the recording could not be written: {e}") })?;
        Ok(outcome)
    }
}

impl Database for Recorder<'_> {
    fn execute(&mut self, call: &Call) -> Answer {
        let a = self.inner.execute(call);
        self.record(call, a)
    }
    fn open(&mut self, call: &Call) -> Answer {
        let a = self.inner.open(call);
        self.record(call, a)
    }
    fn fetch(&mut self, call: &Call) -> Answer {
        let a = self.inner.fetch(call);
        self.record(call, a)
    }
    fn close(&mut self, call: &Call) -> Answer {
        let a = self.inner.close(call);
        self.record(call, a)
    }
    fn commit(&mut self, call: &Call) -> Answer {
        let a = self.inner.commit(call);
        self.record(call, a)
    }
    fn rollback(&mut self, call: &Call) -> Answer {
        let a = self.inner.rollback(call);
        self.record(call, a)
    }
    fn close_all(&mut self) -> Result<(), Abandoned> {
        self.inner.close_all()
    }
}

fn entry_text(seq: u64, call: &Call, outcome: &Outcome) -> String {
    let cursor = call.cursor.map(|c| format!(" {c}")).unwrap_or_default();
    let mut text = format!("@ {seq} {}:{}:{:08x} {}{cursor}\n", call.program, call.ordinal, fingerprint(call.text), call.verb);
    if !call.inputs.is_empty() {
        text += &format!("> {}\n", values_text(call.inputs));
    }
    text += &format!("< {} {} rows={}", outcome.sqlcode, outcome.sqlstate, outcome.affected);
    if !outcome.tokens.is_empty() {
        text += &format!(" tokens={}", value_text(&Value::Char(outcome.tokens.clone())));
    }
    text.push('\n');
    for row in &outcome.rows {
        text += &format!("= {}\n", values_text(row));
    }
    text
}

fn values_text(values: &[Value]) -> String {
    values.iter().map(value_text).collect::<Vec<_>>().join(" | ")
}

fn value_text(v: &Value) -> String {
    match v {
        Value::Null => "null".into(),
        Value::Int(i) => format!("int:{i}"),
        Value::Decimal { value, scale } => format!("dec:{}", Value::decimal_text(*value, *scale)),
        Value::Double(f) => format!("double:{f:?}"),
        Value::Char(s) => {
            let mut q = String::from("char:\"");
            for c in s.chars() {
                match c {
                    '"' => q += "\\\"",
                    '\\' => q += "\\\\",
                    c if c.is_control() => q += &format!("\\x{:02X}", c as u32),
                    c => q.push(c),
                }
            }
            q + "\""
        }
        Value::Binary(b) => format!("hex:{}", b.iter().map(|x| format!("{x:02X}")).collect::<String>()),
    }
}

fn parse_outcome(text: &str) -> Result<Outcome, String> {
    let mut words = text.splitn(4, ' ');
    let (Some(code), Some(state), Some(rows)) = (words.next(), words.next(), words.next()) else { return Err("< takes SQLCODE, SQLSTATE and rows=N".into()) };
    let sqlcode = code.parse().map_err(|_| format!("{code} is not an SQLCODE"))?;
    if state.len() != 5 {
        return Err(format!("{state} is not a five-character SQLSTATE"));
    }
    let affected = rows.strip_prefix("rows=").and_then(|n| n.parse().ok()).ok_or_else(|| format!("{rows} is not rows=N"))?;
    let tokens = match words.next().map(str::trim) {
        None | Some("") => String::new(),
        Some(t) => match t.strip_prefix("tokens=").map(parse_value) {
            Some(Ok((Value::Char(s), rest))) if rest.trim().is_empty() => s,
            _ => return Err("the rest of a < line is tokens=char:\"...\"".into()),
        },
    };
    Ok(Outcome { sqlcode, sqlstate: state.into(), affected, rows: Vec::new(), tokens })
}

fn parse_values(text: &str) -> Result<Vec<Value>, String> {
    let (mut out, mut rest) = (Vec::new(), text.trim_start());
    while !rest.is_empty() {
        let (v, after) = parse_value(rest)?;
        out.push(v);
        rest = after.trim_start();
        if let Some(next) = rest.strip_prefix('|') {
            rest = next.trim_start();
            if rest.is_empty() {
                return Err("a value is missing after |".into());
            }
        } else if !rest.is_empty() {
            return Err(format!("values are separated by |, not \"{rest}\""));
        }
    }
    Ok(out)
}

/// One value literal from the start of `text`, and what follows it.
fn parse_value(text: &str) -> Result<(Value, &str), String> {
    if let Some(quoted) = text.strip_prefix("char:\"") {
        let mut s = String::new();
        let mut chars = quoted.char_indices();
        while let Some((i, c)) = chars.next() {
            match c {
                '"' => return Ok((Value::Char(s), &quoted[i + 1..])),
                '\\' => match chars.next() {
                    Some((_, '"')) => s.push('"'),
                    Some((_, '\\')) => s.push('\\'),
                    Some((j, 'x')) => {
                        let hex = quoted.get(j + 1..j + 3).ok_or("\\x takes two hexadecimal digits")?;
                        let code = u32::from_str_radix(hex, 16).map_err(|_| format!("\\x{hex} is not hexadecimal"))?;
                        s.push(char::from_u32(code).ok_or("\\x names no character")?);
                        chars.next();
                        chars.next();
                    }
                    _ => return Err("a backslash in char:\"...\" escapes \", \\ or xNN".into()),
                },
                c => s.push(c),
            }
        }
        return Err("char:\" is not closed".into());
    }
    let end = text.find(|c: char| c.is_whitespace() || c == '|').unwrap_or(text.len());
    let (word, rest) = text.split_at(end);
    let value = match word.split_once(':') {
        None if word == "null" => Value::Null,
        Some(("int", n)) => Value::Int(n.parse().map_err(|_| format!("{word} is not an integer"))?),
        Some(("dec", n)) => Value::parse_decimal(n).ok_or_else(|| format!("{word} is not a decimal"))?,
        Some(("double", n)) => Value::Double(n.parse().map_err(|_| format!("{word} is not a double"))?),
        Some(("hex", h)) if h.len() % 2 == 0 => {
            let bytes: Result<Vec<u8>, _> = (0..h.len()).step_by(2).map(|i| u8::from_str_radix(&h[i..i + 2], 16)).collect();
            Value::Binary(bytes.map_err(|_| format!("{word} is not hexadecimal"))?)
        }
        _ => return Err(format!("{word} is not a value: null, int:, dec:, double:, char:\"...\" or hex:")),
    };
    Ok((value, rest))
}

#[cfg(test)]
mod tests {
    use super::*;

    fn call<'a>(verb: &'a str, text: &'a str, inputs: &'a [Value]) -> Call<'a> {
        Call { program: "P", ordinal: 2, verb, cursor: None, text, inputs }
    }

    #[test]
    fn values_round_trip() {
        let values = vec![
            Value::Null,
            Value::Int(-42),
            Value::Decimal { value: -123_450, scale: 2 },
            Value::Decimal { value: 5, scale: 2 },
            Value::Decimal { value: 7, scale: 0 },
            Value::Double(0.1),
            Value::Double(6.02e23),
            Value::Char("say \"hi\" | x \\ é\n".into()),
            Value::Binary(vec![0xC1, 0x00]),
        ];
        let text = values_text(&values);
        assert!(text.contains("dec:-1234.50") && text.contains("dec:0.05") && text.contains("dec:7"), "{text}");
        assert_eq!(parse_values(&text), Ok(values));
    }

    #[test]
    fn a_recording_answers_the_calls_it_holds_in_order() {
        let inputs = [Value::Int(7)];
        let first = entry_text(1, &call("SELECT", "SELECT A FROM T WHERE K = ?", &inputs), &Outcome::rows(vec![vec![Value::Char("X".into())]]));
        let second = entry_text(2, &call("COMMIT", "COMMIT", &[]), &Outcome::ok());
        let mut replay = Replay::parse(&format!("{HEADER}\n{first}{second}"), false).expect("parses");
        assert_eq!(replay.execute(&call("SELECT", "SELECT A FROM T WHERE K = ?", &inputs)).unwrap().rows, [[Value::Char("X".into())]]);
        assert_eq!(replay.commit(&call("COMMIT", "COMMIT", &[])), Ok(Outcome::ok()));
        let beyond = replay.commit(&call("COMMIT", "COMMIT", &[])).unwrap_err();
        assert_eq!((beyond.code, beyond.message.starts_with("the recording holds no such call")), ("SQLR", true));
    }

    #[test]
    fn strict_replay_refuses_a_different_call_and_names_both() {
        let text = format!("{HEADER}\n{}", entry_text(1, &call("SELECT", "SELECT A FROM T WHERE K = ?", &[Value::Int(7)]), &Outcome::ok()));
        let mut replay = Replay::parse(&text, false).unwrap();
        let err = replay.execute(&call("SELECT", "SELECT A FROM T WHERE K = ?", &[Value::Int(8)])).unwrap_err();
        assert_eq!(err.code, "SQLR");
        assert!(err.message.contains("with int:7") && err.message.contains("with int:8"), "{}", err.message);
    }

    #[test]
    fn keyed_replay_takes_calls_in_any_order() {
        let (a, b) = ([Value::Int(1)], [Value::Int(2)]);
        let text = format!(
            "{HEADER}\n{}{}",
            entry_text(1, &call("SELECT", "Q", &a), &Outcome::rows(vec![vec![Value::Int(10)]])),
            entry_text(2, &call("SELECT", "Q", &b), &Outcome::rows(vec![vec![Value::Int(20)]]))
        );
        let mut replay = Replay::parse(&text, true).unwrap();
        assert_eq!(replay.execute(&call("SELECT", "Q", &b)).unwrap().rows, [[Value::Int(20)]]);
        assert_eq!(replay.execute(&call("SELECT", "Q", &a)).unwrap().rows, [[Value::Int(10)]]);
        assert!(replay.execute(&call("SELECT", "Q", &a)).is_err());
    }

    #[test]
    fn a_recorder_writes_what_replay_reads() {
        struct Fixed;
        impl Database for Fixed {
            fn execute(&mut self, _: &Call) -> Answer {
                Ok(Outcome { tokens: "T1".into(), ..Outcome::rows(vec![vec![Value::Decimal { value: 150, scale: 2 }, Value::Null]]) })
            }
            fn open(&mut self, _: &Call) -> Answer {
                Ok(Outcome::ok())
            }
            fn fetch(&mut self, _: &Call) -> Answer {
                Ok(Outcome::error(100, "02000"))
            }
            fn close(&mut self, _: &Call) -> Answer {
                Ok(Outcome::ok())
            }
            fn commit(&mut self, _: &Call) -> Answer {
                Ok(Outcome::ok())
            }
            fn rollback(&mut self, _: &Call) -> Answer {
                Ok(Outcome::ok())
            }
        }
        let written = std::rc::Rc::new(std::cell::RefCell::new(Vec::new()));
        struct Sink(std::rc::Rc<std::cell::RefCell<Vec<u8>>>);
        impl Write for Sink {
            fn write(&mut self, b: &[u8]) -> std::io::Result<usize> {
                self.0.borrow_mut().extend_from_slice(b);
                Ok(b.len())
            }
            fn flush(&mut self) -> std::io::Result<()> {
                Ok(())
            }
        }
        let inputs = [Value::Char("A|B".into())];
        let mut recorder = Recorder::new(Box::new(Fixed), Box::new(Sink(written.clone())), "a test double").unwrap();
        let live = recorder.execute(&call("SELECT", "SELECT X, Y FROM T WHERE Z = ?", &inputs)).unwrap();
        let text = String::from_utf8(written.borrow().clone()).unwrap();
        assert!(text.starts_with(&format!("{HEADER}\n# source: a test double\n")), "{text}");
        let mut replay = Replay::parse(&text, false).unwrap();
        assert_eq!(replay.execute(&call("SELECT", "SELECT X, Y FROM T WHERE Z = ?", &inputs)), Ok(live));
    }

    #[test]
    fn malformed_recordings_name_the_line() {
        assert_eq!(Replay::parse("@ 1 P:1:0 SELECT\n< 0 00000 rows=0\n", false).err().unwrap(), format!("line 1: a recording starts with \"{HEADER}\""));
        let err = Replay::parse(&format!("{HEADER}\n@ 1 P:1:0 SELECT\n= int:1\n"), false).err().unwrap();
        assert_eq!(err, "line 3: an = line belongs after a < line");
        assert!(Replay::parse(&format!("{HEADER}\n@ 1 P:1:0 SELECT\n< 0 00000 rows=0\n= int:x\n"), false).err().unwrap().starts_with("line 4: "));
        assert_eq!(Replay::parse(&format!("{HEADER}\n@ 1 P:1:0 SELECT\n"), false).err().unwrap(), "the last call has no < line");
    }
}