specfold-core 0.4.0

//! Changing frontmatter through assignments (`key=value`, `key+=value`, `key-=value`), with the
//! lifecycle enforced and `updated` kept current.

use super::plan::Plan;
use crate::corpus::Corpus;
use crate::markdown::frontmatter::edit;
use crate::model::stamp;
use anyhow::{Result, anyhow, bail};
use serde_json::{Map, Value};

#[derive(Debug, Clone, PartialEq, Eq)]
pub enum Op {
    Set,
    Add,
    Remove,
}

#[derive(Debug, Clone)]
pub struct Assign {
    /// `status`, `phase`, `tags`, `rel.implements` …
    pub key: String,
    pub op: Op,
    pub value: String,
}

impl Assign {
    pub fn parse(s: &str) -> Result<Self> {
        for (token, op) in [("+=", Op::Add), ("-=", Op::Remove), ("=", Op::Set)] {
            if let Some((k, v)) = s.split_once(token) {
                if k.is_empty() {
                    break;
                }
                return Ok(Assign { key: k.trim().to_string(), op, value: v.trim().to_string() });
            }
        }
        bail!("'{s}' is not key=value, key+=value or key-=value")
    }
}

const PROTECTED: &[&str] = &["id", "created", "files"];
const LIST_KEYS: &[&str] = &["tags", "owners", "aliases", "verify", "check_skip", "screens"];

fn target<'a>(map: &'a mut Map<String, Value>, key: &str) -> (&'a mut Map<String, Value>, String) {
    match key.split_once('.') {
        Some((parent, child)) => {
            let entry = map.entry(parent.to_string()).or_insert_with(|| Value::Object(Map::new()));
            if !entry.is_object() {
                *entry = Value::Object(Map::new());
            }
            (entry.as_object_mut().expect("entry was just made an object"), child.to_string())
        }
        None => (map, key.to_string()),
    }
}

/// Frontmatter keys that hold one value.
const SCALAR_KEYS: &[&str] = &["id", "title", "status", "owner", "created", "updated", "source_rev"];

fn apply_one(map: &mut Map<String, Value>, a: &Assign) {
    // C109: `key=[a, b]` is a list, written the way YAML writes one.
    // C200: a single-value key keeps `[x, y]` as text (the writer quotes it), not a list.
    let scalar = SCALAR_KEYS.contains(&a.key.as_str());
    let bracketed = a.value.trim().strip_prefix('[').and_then(|v| v.strip_suffix(']')).filter(|_| !scalar);
    let is_list = bracketed.is_some() || a.key.starts_with("rel.") || LIST_KEYS.contains(&a.key.as_str());
    let value = if let (Op::Set, Some(inner)) = (&a.op, bracketed) {
        if inner.trim().is_empty() {
            let (m, k) = target(map, &a.key);
            m.insert(k, Value::Array(vec![]));
            return;
        }
        inner.to_string()
    } else if a.key == "updated" && a.value == "today" {
        stamp::now_value()
    } else {
        a.value.clone()
    };
    let nested = a.key.contains('.');
    let (m, k) = target(map, &a.key);
    // `key=` with nothing after it deletes the key, so an unknown relation can be taken out.
    if matches!(a.op, Op::Set) && value.is_empty() {
        m.remove(&k);
        if nested {
            let parent = a.key.split('.').next().unwrap_or_default();
            if map.get(parent).is_some_and(|v| v.as_object().is_some_and(|o| o.is_empty())) {
                map.remove(parent);
            }
        }
        return;
    }
    match (&a.op, is_list) {
        (Op::Set, true) => {
            m.insert(
                k,
                Value::Array(
                    value
                        .split(',')
                        .map(|s| Value::String(s.trim().into()))
                        .filter(|v| v.as_str() != Some(""))
                        .collect(),
                ),
            );
        }
        (Op::Set, false) => {
            m.insert(k, Value::String(value));
        }
        (Op::Add, _) => {
            let list = m.entry(k).or_insert_with(|| Value::Array(vec![]));
            if let Value::Array(items) = list
                && !items.iter().any(|x| x.as_str() == Some(value.as_str()))
            {
                items.push(Value::String(value));
            }
        }
        (Op::Remove, _) => match m.get_mut(&k) {
            Some(Value::Array(items)) => items.retain(|x| x.as_str() != Some(value.as_str())),
            Some(Value::Object(entries)) => {
                entries.remove(&value);
                if entries.is_empty() {
                    m.remove(&k);
                }
            }
            _ => {}
        },
    }
}

/// What to run instead of a refused status move: never the command that was just refused.
fn move_hint(ty: &crate::model::doctype::TypeDef, from: &str, to: &str, id: &str) -> String {
    let next: Vec<&str> =
        ty.statuses.iter().map(String::as_str).filter(|s| *s != from && ty.transition_allowed(from, s)).collect();
    if to == "superseded" && from == "draft" {
        return format!(
            "a draft has not taken effect, so nothing supersedes it: make it active first with `spec set {} status=active --write`, then run `spec new {} --title '…' --from {} --write`; or change the draft itself with `spec edit {} --text '…' --write`",
            crate::shell::word(id),
            ty.name,
            crate::shell::word(id),
            crate::shell::word(id)
        );
    }
    if to == "superseded" && ty.transition_allowed("active", "superseded") && from != "active" {
        return format!("only an active {} can be superseded, and this one is {from}", ty.name);
    }
    if next.is_empty() {
        format!("'{from}' is final")
    } else {
        format!("from '{from}' it can move to: {}", next.join(", "))
    }
}

/// The status a word for "finished" most likely means: types name the end of their work
/// differently (`archived`, `done`, `closed`), so a near miss gets the real one suggested.
fn finishing_status<'a>(asked: &str, reachable: &[&'a String]) -> Option<&'a str> {
    const FINISHED: &[&str] = &["done", "complete", "completed", "finished", "closed", "resolved", "archived"];
    if !FINISHED.contains(&asked.to_lowercase().as_str()) {
        return None;
    }
    FINISHED.iter().find_map(|f| reachable.iter().find(|s| s.as_str() == *f).map(|s| s.as_str()))
}

pub fn plan(c: &Corpus, idx: usize, assigns: &[Assign]) -> Result<Plan> {
    plan_with(c, idx, assigns, false)
}

/// The old document's half of `spec new --from`: its successor is written in the same change.
pub fn plan_superseded_by_new(c: &Corpus, idx: usize) -> Result<Plan> {
    plan_with(c, idx, &[Assign::parse("status=superseded")?], true)
}

fn plan_with(c: &Corpus, idx: usize, assigns: &[Assign], successor_pending: bool) -> Result<Plan> {
    let d = &c.docs[idx];
    let ty = c.cfg.registry.get(&d.id.ty).ok_or_else(|| anyhow!("unknown type {}", d.id.ty))?;
    for a in assigns {
        if PROTECTED.contains(&a.key.as_str()) {
            bail!(
                "{} cannot be set by hand: id comes from the path (spec mv), created is fixed, files is managed by spec attach",
                a.key
            );
        }
        // C128: title is required (S1), so it can be changed but not emptied.
        if a.key == "title" && matches!(a.op, Op::Set) && a.value.trim().is_empty() {
            bail!("title is required and cannot be emptied; give a new one: spec set {} title='…' --write", d.id);
        }
        // C223: updated is required (S1) as well; `updated=` would delete it.
        if a.key == "updated" && matches!(a.op, Op::Set) && a.value.trim().is_empty() {
            bail!("updated is required and cannot be emptied; give a date: spec set {} updated=today --write", d.id);
        }
        if a.key == "status" {
            if !ty.statuses.contains(&a.value) {
                let from = d.status().unwrap_or_else(|| ty.initial.clone());
                let reachable: Vec<&String> =
                    ty.statuses.iter().filter(|s| **s != from && ty.transition_allowed(&from, s)).collect();
                let pick = finishing_status(&a.value, &reachable);
                let next = pick
                    .map(|s| format!("; next: spec set {} status={s} --write", crate::shell::word(&d.id)))
                    .unwrap_or_default();
                bail!(
                    "status '{}' is not allowed for {} (allowed: {}; from '{from}': {}){next}",
                    a.value,
                    ty.name,
                    ty.statuses.join(", "),
                    reachable.iter().map(|s| s.as_str()).collect::<Vec<_>>().join(", ")
                );
            }
            let from = d.status().unwrap_or_else(|| ty.initial.clone());
            if !ty.transition_allowed(&from, &a.value) {
                bail!(
                    "status cannot move from '{from}' to '{}'; {}",
                    a.value,
                    move_hint(ty, &from, &a.value, &d.id.to_string())
                );
            }
            // superseded without a successor is a T1 error the moment it is written.
            let me = d.id.to_string();
            let succeeded = c
                .docs
                .iter()
                .filter(|o| o.id.ty == d.id.ty) // C204: L3 refuses a cross-type supersedes
                .any(|o| o.rel().get("supersedes").is_some_and(|l| l.iter().any(|x| x.trim_matches(['[', ']']) == me)));
            if a.value == "superseded" && !succeeded && !successor_pending {
                let title = d.title.clone().unwrap_or_else(|| d.slug.replace('-', " ")).replace('\'', "");
                bail!(
                    "nothing supersedes {me} yet, so status=superseded would fail T1; write the successor, which marks this one superseded (edit the title); next: spec new {} --from {me} --title '{title}' --write",
                    ty.name
                );
            }
        }
    }
    // A pin names a commit; HEAD is resolved now, since HEAD moves.
    let pinned: Vec<Assign>;
    let assigns = if assigns.iter().any(|a| a.key == "verified_at" && a.value == "HEAD") {
        let head = crate::workspace::vcs::head(&c.cfg.root)
            .ok_or_else(|| anyhow!("verified_at=HEAD needs a git repository with a commit"))?;
        pinned = assigns
            .iter()
            .map(|a| {
                let mut a = a.clone();
                if a.key == "verified_at" && a.value == "HEAD" {
                    a.value = head.chars().take(12).collect();
                }
                a
            })
            .collect();
        &pinned[..]
    } else {
        assigns
    };
    let text = crate::corpus::overlay::read(&c.cfg.root.join(&d.path))?;
    // C117: values that are already there change nothing, so nothing is written and `updated` stays.
    let order = |m: &mut Map<String, Value>| {
        let ordered = edit::ordered(std::mem::take(m));
        *m = ordered;
    };
    let same = edit::rewrite(&text, |m| {
        for a in assigns {
            apply_one(m, a);
        }
        order(m);
    })? == edit::rewrite(&text, order)?;
    if same {
        return Ok(Plan::default());
    }
    let new = edit::rewrite(&text, |m| {
        for a in assigns {
            apply_one(m, a);
        }
        if !assigns.iter().any(|a| a.key == "updated") {
            m.insert("updated".into(), Value::String(stamp::now_value()));
        }
        let ordered = edit::ordered(std::mem::take(m));
        *m = ordered;
    })?;
    let mut p = Plan::default();
    p.write(&d.path, new, false);
    Ok(p)
}

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

    #[test]
    fn parses_and_applies() {
        let mut m = Map::new();
        apply_one(&mut m, &Assign::parse("rel.implements+=sot:a/b").unwrap());
        apply_one(&mut m, &Assign::parse("rel.implements+=sot:a/b").unwrap());
        apply_one(&mut m, &Assign::parse("approvers=[kim, lee]").unwrap());
        assert_eq!(m["approvers"], serde_json::json!(["kim", "lee"]), "C109");
        apply_one(&mut m, &Assign::parse("tags=x, y").unwrap());
        apply_one(&mut m, &Assign::parse("phase=P3").unwrap());
        assert_eq!(m["rel"]["implements"], serde_json::json!(["sot:a/b"]));
        assert_eq!(m["tags"], serde_json::json!(["x", "y"]));
        apply_one(&mut m, &Assign::parse("tags-=x").unwrap());
        apply_one(&mut m, &Assign::parse("rel.affects=a").unwrap());
        apply_one(&mut m, &Assign::parse("rel.affects=").unwrap());
        assert!(m["rel"].get("affects").is_none());
        assert_eq!(m["tags"], serde_json::json!(["y"]));
        assert!(Assign::parse("=x").is_err());
    }
}