chappi-core 0.1.0

use std::collections::{HashMap, HashSet};

use chappi_syntax::{
    Atom, Form, FormKind, Span, is_canonical_decimal, is_canonical_integer, is_canonical_symbol,
    is_canonical_text,
};

use crate::diagnostic::error;
use crate::focus::validate_focus_streams;
use crate::patch::{AddValue, Patch, PatchOp};
use crate::{
    CognitiveState, Diagnostic, FocusFrame, Node, NodeKind, Relation, RelationKind, Source,
};

pub fn validate(state: &CognitiveState) -> Vec<Diagnostic> {
    let mut diagnostics = Vec::new();
    let mut nodes_by_id = HashMap::new();

    validate_canonical_domain(state, &mut diagnostics);

    for node in &state.nodes {
        if node.salience > 100 {
            diagnostics.push(error(
                "invalid-salience",
                node.span,
                vec!["nodes".into(), node.id.clone(), "salience".into()],
                "salience must be an integer from 0 through 100",
                None,
            ));
        }
        if nodes_by_id.contains_key(node.id.as_str()) {
            diagnostics.push(error(
                "duplicate-node-id",
                node.span,
                vec!["nodes".into(), node.id.clone(), "id".into()],
                format!("node ID `{}` is defined more than once", node.id),
                Some("use a unique stable ID for every node".into()),
            ));
        } else {
            nodes_by_id.insert(node.id.as_str(), node);
        }
    }

    for node in &state.nodes {
        validate_entity_reference(
            &nodes_by_id,
            node,
            &node.owner,
            "owner",
            "undefined-owner",
            "invalid-owner-kind",
            &mut diagnostics,
        );

        match &node.kind {
            NodeKind::Relationship { target, .. }
            | NodeKind::Affect { target, .. }
            | NodeKind::Perspective(crate::Perspective { target, .. }) => {
                validate_entity_reference(
                    &nodes_by_id,
                    node,
                    target,
                    "target",
                    "undefined-entity-target",
                    "invalid-entity-target-kind",
                    &mut diagnostics,
                );
            }
            _ => {}
        }
    }

    let mut seen_relations = HashSet::new();
    for relation in &state.relations {
        let key = (
            relation.kind,
            relation.source.as_str(),
            relation.target.as_str(),
        );
        if !seen_relations.insert(key) {
            diagnostics.push(error(
                "duplicate-relation",
                relation.span,
                relation_path(relation),
                format!(
                    "relation `({} {} {})` is defined more than once",
                    relation.kind.as_str(),
                    relation.source,
                    relation.target
                ),
                Some("remove the duplicate relation".into()),
            ));
        }

        let source = nodes_by_id.get(relation.source.as_str()).copied();
        let target = nodes_by_id.get(relation.target.as_str()).copied();
        if source.is_none() {
            let mut path = relation_path(relation);
            path.push("source".into());
            diagnostics.push(error(
                "undefined-relation-source",
                relation.span,
                path,
                format!(
                    "relation source `{}` does not name an existing node",
                    relation.source
                ),
                None,
            ));
        }
        if target.is_none() {
            let mut path = relation_path(relation);
            path.push("target".into());
            diagnostics.push(error(
                "undefined-relation-target",
                relation.span,
                path,
                format!(
                    "relation target `{}` does not name an existing node",
                    relation.target
                ),
                None,
            ));
        }
        let (Some(source), Some(target)) = (source, target) else {
            continue;
        };
        if !relation_endpoints_allowed(relation.kind, &source.kind, &target.kind) {
            diagnostics.push(error(
                "invalid-relation-endpoints",
                relation.span,
                relation_path(relation),
                format!(
                    "relation kind `{}` does not permit {} -> {}",
                    relation.kind.as_str(),
                    node_kind_name(&source.kind),
                    node_kind_name(&target.kind)
                ),
                Some("choose endpoint node kinds allowed by the v1 relation matrix".into()),
            ));
        }
    }

    validate_supersession_cycles(state, &nodes_by_id, &mut diagnostics);
    validate_focus_streams(state, &nodes_by_id, &mut diagnostics);
    diagnostics
}

/// Validates that every value retained by a typed patch can be encoded and
/// decoded without changing its meaning.
pub fn validate_patch(patch: &Patch) -> Vec<Diagnostic> {
    let mut diagnostics = Vec::new();
    if patch.version != 1 {
        diagnostics.push(error(
            "invalid-patch-version",
            patch.span,
            vec!["header".into(), "version".into()],
            format!("patch version must be 1, not {}", patch.version),
            None,
        ));
    }

    for (index, op) in patch.ops.iter().enumerate() {
        let root = vec!["ops".into(), index.to_string()];
        match op {
            PatchOp::Add(op) => match &op.value {
                AddValue::Node(node) => {
                    validate_node_canonical(node, child(&root, "add"), &mut diagnostics)
                }
                AddValue::Relation(relation) => {
                    validate_relation_canonical(relation, child(&root, "add"), &mut diagnostics)
                }
            },
            PatchOp::Revise(op) => {
                validate_node_canonical(&op.node, child(&root, "revise"), &mut diagnostics)
            }
            PatchOp::Retire(op) => {
                let retire_root = child(&root, "retire");
                validate_symbol_value(
                    &op.node_id,
                    op.span,
                    child(&retire_root, "node_id"),
                    &mut diagnostics,
                );
                validate_form(&op.reason, child(&retire_root, "reason"), &mut diagnostics);
            }
            PatchOp::AppendFocus(op) => validate_focus_frame_canonical(
                &op.frame,
                child(&root, "append_focus"),
                &mut diagnostics,
            ),
        }
    }
    diagnostics
}

fn validate_canonical_domain(state: &CognitiveState, diagnostics: &mut Vec<Diagnostic>) {
    if state.version != 1 {
        diagnostics.push(error(
            "invalid-version",
            empty_span(),
            vec!["version".into()],
            format!("state version must be 1, not {}", state.version),
            None,
        ));
    }

    for node in &state.nodes {
        let root = vec!["nodes".into(), node.id.clone()];
        validate_node_canonical(node, root, diagnostics);
    }

    for relation in &state.relations {
        let root = relation_path(relation);
        validate_relation_canonical(relation, root, diagnostics);
    }

    for stream in &state.focus_streams {
        let stream_root = vec!["focus".into(), stream.id.clone()];
        let stream_span = stream
            .frames
            .first()
            .map_or_else(empty_span, |frame| frame.span);
        validate_symbol_value(
            &stream.id,
            stream_span,
            child(&stream_root, "id"),
            diagnostics,
        );
        for frame in &stream.frames {
            let frame_root = vec![
                "focus".into(),
                stream.id.clone(),
                frame.sequence.to_string(),
            ];
            validate_focus_frame_canonical(frame, frame_root, diagnostics);
        }
    }
}

fn validate_node_canonical(node: &Node, root: Vec<String>, diagnostics: &mut Vec<Diagnostic>) {
    validate_symbol_value(&node.id, node.span, child(&root, "id"), diagnostics);
    validate_symbol_value(&node.owner, node.span, child(&root, "owner"), diagnostics);
    match &node.kind {
        NodeKind::Entity { entity_kind } => validate_symbol_value(
            entity_kind,
            node.span,
            child(&root, "entity_kind"),
            diagnostics,
        ),
        NodeKind::Evidence {
            evidence_kind,
            source,
        } => {
            validate_symbol_value(
                evidence_kind,
                node.span,
                child(&root, "evidence_kind"),
                diagnostics,
            );
            match source {
                Source::Symbol(value) => {
                    validate_symbol_value(value, node.span, child(&root, "source"), diagnostics)
                }
                Source::String(value) => {
                    validate_text_value(value, node.span, child(&root, "source"), diagnostics)
                }
            }
        }
        NodeKind::Relationship { target, status } => {
            validate_symbol_value(target, node.span, child(&root, "target"), diagnostics);
            validate_symbol_value(status, node.span, child(&root, "status"), diagnostics);
        }
        NodeKind::Perspective(value) => validate_symbol_value(
            &value.target,
            node.span,
            child(&root, "target"),
            diagnostics,
        ),
        NodeKind::Affect {
            target,
            affect_kind,
            ..
        } => {
            validate_symbol_value(target, node.span, child(&root, "target"), diagnostics);
            validate_symbol_value(
                affect_kind,
                node.span,
                child(&root, "affect_kind"),
                diagnostics,
            );
        }
        NodeKind::Claim { .. }
        | NodeKind::Goal { .. }
        | NodeKind::Constraint { .. }
        | NodeKind::Question { .. }
        | NodeKind::Desire { .. }
        | NodeKind::Attention { .. }
        | NodeKind::Association
        | NodeKind::Tension { .. }
        | NodeKind::Prediction { .. }
        | NodeKind::Metacognition { .. } => {}
    }
    validate_form(&node.payload, child(&root, "payload"), diagnostics);
}

fn validate_relation_canonical(
    relation: &Relation,
    root: Vec<String>,
    diagnostics: &mut Vec<Diagnostic>,
) {
    validate_symbol_value(
        &relation.source,
        relation.span,
        child(&root, "source"),
        diagnostics,
    );
    validate_symbol_value(
        &relation.target,
        relation.span,
        child(&root, "target"),
        diagnostics,
    );
}

fn validate_focus_frame_canonical(
    frame: &FocusFrame,
    root: Vec<String>,
    diagnostics: &mut Vec<Diagnostic>,
) {
    validate_symbol_value(
        &frame.stream_id,
        frame.span,
        child(&root, "stream_id"),
        diagnostics,
    );
    validate_symbol_value(&frame.owner, frame.span, child(&root, "owner"), diagnostics);
    for (bucket_name, bucket) in [
        ("fg", &frame.foreground),
        ("bg", &frame.background),
        ("residue", &frame.residue),
    ] {
        for (index, reference) in bucket.iter().enumerate() {
            let mut path = child(&root, bucket_name);
            path.push(index.to_string());
            validate_symbol_value(reference, frame.span, path, diagnostics);
        }
    }
    validate_form(&frame.trigger, child(&root, "trigger"), diagnostics);
}

fn validate_form(form: &Form, path: Vec<String>, diagnostics: &mut Vec<Diagnostic>) {
    match &form.kind {
        FormKind::Atom(Atom::Symbol(value)) => {
            validate_symbol_value(value, form.span, path, diagnostics)
        }
        FormKind::Atom(Atom::String(value)) => {
            validate_text_value(value, form.span, path, diagnostics)
        }
        FormKind::Atom(Atom::Integer(value)) if !is_canonical_integer(value) => {
            diagnostics.push(error(
                "noncanonical-integer",
                form.span,
                path,
                format!("integer `{value}` does not have canonical spelling"),
                Some("write the integer without redundant leading zeros".into()),
            ));
        }
        FormKind::Atom(Atom::Decimal(value)) if !is_canonical_decimal(value) => {
            diagnostics.push(error(
                "noncanonical-decimal",
                form.span,
                path,
                format!("decimal `{value}` does not have canonical spelling"),
                Some("remove redundant leading and trailing zeros".into()),
            ));
        }
        FormKind::List(items) => {
            for (index, item) in items.iter().enumerate() {
                let mut item_path = path.clone();
                item_path.push(index.to_string());
                validate_form(item, item_path, diagnostics);
            }
        }
        FormKind::Atom(Atom::Integer(_) | Atom::Decimal(_)) => {}
    }
}

fn validate_symbol_value(
    value: &str,
    span: Span,
    path: Vec<String>,
    diagnostics: &mut Vec<Diagnostic>,
) {
    if !is_canonical_symbol(value) {
        diagnostics.push(error(
            "noncanonical-symbol",
            span,
            path,
            format!("symbol `{value}` is not round-trip-safe canonical syntax"),
            Some("use an NFC symbol that is neither numeric nor delimiter-containing".into()),
        ));
    }
}

fn validate_text_value(
    value: &str,
    span: Span,
    path: Vec<String>,
    diagnostics: &mut Vec<Diagnostic>,
) {
    if !is_canonical_text(value) {
        diagnostics.push(error(
            "noncanonical-text",
            span,
            path,
            "text is not NFC-normalized",
            Some("normalize text to Unicode NFC before encoding".into()),
        ));
    }
}

fn child(root: &[String], field: &str) -> Vec<String> {
    let mut path = root.to_vec();
    path.push(field.into());
    path
}

fn empty_span() -> Span {
    Span {
        start: 0,
        end: 0,
        start_line: 1,
        start_column: 1,
        end_line: 1,
        end_column: 1,
    }
}

fn validate_entity_reference(
    nodes_by_id: &HashMap<&str, &Node>,
    node: &Node,
    reference: &str,
    field: &str,
    undefined_code: &str,
    wrong_kind_code: &str,
    diagnostics: &mut Vec<Diagnostic>,
) {
    let path = vec!["nodes".into(), node.id.clone(), field.into()];
    match nodes_by_id.get(reference) {
        None => diagnostics.push(error(
            undefined_code,
            node.span,
            path,
            format!("{field} `{reference}` does not name an existing entity node"),
            None,
        )),
        Some(target) if !matches!(target.kind, NodeKind::Entity { .. }) => {
            diagnostics.push(error(
                wrong_kind_code,
                node.span,
                path,
                format!("{field} `{reference}` names a non-entity node"),
                Some("refer to the stable ID of an entity node".into()),
            ));
        }
        Some(_) => {}
    }
}

fn relation_endpoints_allowed(kind: RelationKind, source: &NodeKind, target: &NodeKind) -> bool {
    match kind {
        RelationKind::Supports | RelationKind::Contradicts => {
            matches!(source, NodeKind::Evidence { .. } | NodeKind::Claim { .. })
                && matches!(target, NodeKind::Claim { .. } | NodeKind::Prediction { .. })
        }
        RelationKind::Refines | RelationKind::Supersedes => {
            std::mem::discriminant(source) == std::mem::discriminant(target)
        }
        RelationKind::Causes => matches!(
            target,
            NodeKind::Claim { .. }
                | NodeKind::Goal { .. }
                | NodeKind::Desire { .. }
                | NodeKind::Affect { .. }
                | NodeKind::Prediction { .. }
                | NodeKind::Tension { .. }
        ),
        RelationKind::About => matches!(target, NodeKind::Entity { .. }),
        RelationKind::Blocks => {
            matches!(
                source,
                NodeKind::Constraint { .. } | NodeKind::Tension { .. } | NodeKind::Question { .. }
            ) && matches!(target, NodeKind::Goal { .. } | NodeKind::Desire { .. })
        }
        RelationKind::Associates => true,
    }
}

fn validate_supersession_cycles(
    state: &CognitiveState,
    nodes_by_id: &HashMap<&str, &Node>,
    diagnostics: &mut Vec<Diagnostic>,
) {
    let mut adjacency: HashMap<&str, Vec<&str>> = HashMap::new();

    for relation in &state.relations {
        if relation.kind != RelationKind::Supersedes {
            continue;
        }
        let (Some(source), Some(target)) = (
            nodes_by_id.get(relation.source.as_str()),
            nodes_by_id.get(relation.target.as_str()),
        ) else {
            continue;
        };
        if !relation_endpoints_allowed(relation.kind, &source.kind, &target.kind) {
            continue;
        }

        if reachable(
            &adjacency,
            relation.target.as_str(),
            relation.source.as_str(),
        ) {
            diagnostics.push(error(
                "cyclic-supersession",
                relation.span,
                relation_path(relation),
                format!(
                    "supersession from `{}` to `{}` closes a cycle",
                    relation.source, relation.target
                ),
                Some("supersedes relations must form an acyclic graph".into()),
            ));
        } else {
            adjacency
                .entry(relation.source.as_str())
                .or_default()
                .push(relation.target.as_str());
        }
    }
}

fn reachable(adjacency: &HashMap<&str, Vec<&str>>, start: &str, target: &str) -> bool {
    if start == target {
        return true;
    }
    let mut pending = vec![start];
    let mut visited = HashSet::new();
    while let Some(current) = pending.pop() {
        if !visited.insert(current) {
            continue;
        }
        if let Some(neighbors) = adjacency.get(current) {
            for neighbor in neighbors {
                if *neighbor == target {
                    return true;
                }
                pending.push(neighbor);
            }
        }
    }
    false
}

fn relation_path(relation: &Relation) -> Vec<String> {
    vec![
        "relations".into(),
        relation.kind.as_str().into(),
        relation.source.clone(),
        relation.target.clone(),
    ]
}

fn node_kind_name(kind: &NodeKind) -> &'static str {
    match kind {
        NodeKind::Entity { .. } => "entity",
        NodeKind::Claim { .. } => "claim",
        NodeKind::Evidence { .. } => "evidence",
        NodeKind::Goal { .. } => "goal",
        NodeKind::Constraint { .. } => "constraint",
        NodeKind::Question { .. } => "question",
        NodeKind::Relationship { .. } => "relationship",
        NodeKind::Desire { .. } => "desire",
        NodeKind::Attention { .. } => "attention",
        NodeKind::Association => "association",
        NodeKind::Tension { .. } => "tension",
        NodeKind::Prediction { .. } => "prediction",
        NodeKind::Perspective(_) => "perspective",
        NodeKind::Affect { .. } => "affect",
        NodeKind::Metacognition { .. } => "metacognition",
    }
}