kg/

graph.rs

use std::fs;
use std::io::Write;
use std::path::Path;
use std::time::{SystemTime, UNIX_EPOCH};

use anyhow::{Context, Result};
use flate2::Compression;
use flate2::write::GzEncoder;
use serde::{Deserialize, Serialize};

/// Write `data` to `dest` atomically:
/// 1. Write to `dest.tmp`
/// 2. If `dest` already exists, copy it to `dest.bak`
/// 3. Rename `dest.tmp` -> `dest`
fn atomic_write(dest: &Path, data: &str) -> Result<()> {
    let tmp = dest.with_extension("tmp");
    fs::write(&tmp, data).with_context(|| format!("failed to write tmp: {}", tmp.display()))?;
    if dest.exists() {
        let bak = dest.with_extension("bak");
        fs::copy(dest, &bak)
            .with_context(|| format!("failed to create backup: {}", bak.display()))?;
    }
    fs::rename(&tmp, dest).with_context(|| format!("failed to rename tmp to {}", dest.display()))
}

const BACKUP_STALE_SECS: u64 = 60 * 60;

fn backup_graph_if_stale(path: &Path, data: &str) -> Result<()> {
    let parent = match path.parent() {
        Some(parent) => parent,
        None => return Ok(()),
    };
    let stem = match path.file_stem().and_then(|s| s.to_str()) {
        Some(stem) => stem,
        None => return Ok(()),
    };
    let now = SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .context("time went backwards")?
        .as_secs();
    if let Some(latest) = latest_backup_ts(parent, stem)? {
        if now.saturating_sub(latest) < BACKUP_STALE_SECS {
            return Ok(());
        }
    }

    let backup_path = parent.join(format!("{stem}.bck.{now}.gz"));
    let tmp_path = backup_path.with_extension("tmp");
    let mut encoder = GzEncoder::new(Vec::new(), Compression::default());
    encoder.write_all(data.as_bytes())?;
    let encoded = encoder.finish()?;
    fs::write(&tmp_path, encoded)
        .with_context(|| format!("failed to write tmp: {}", tmp_path.display()))?;
    fs::rename(&tmp_path, &backup_path)
        .with_context(|| format!("failed to rename tmp to {}", backup_path.display()))?;
    Ok(())
}

fn latest_backup_ts(dir: &Path, stem: &str) -> Result<Option<u64>> {
    let prefix = format!("{stem}.bck.");
    let suffix = ".gz";
    let mut latest = None;
    for entry in fs::read_dir(dir).with_context(|| format!("read dir: {}", dir.display()))? {
        let entry = entry?;
        let name = entry.file_name();
        let name = name.to_string_lossy();
        if !name.starts_with(&prefix) || !name.ends_with(suffix) {
            continue;
        }
        let ts_part = &name[prefix.len()..name.len() - suffix.len()];
        if let Ok(ts) = ts_part.parse::<u64>() {
            match latest {
                Some(current) => {
                    if ts > current {
                        latest = Some(ts);
                    }
                }
                None => latest = Some(ts),
            }
        }
    }
    Ok(latest)
}

fn node_type_to_code(node_type: &str) -> &str {
    match node_type {
        "Feature" => "F",
        "Concept" => "K",
        "Interface" => "I",
        "Process" => "P",
        "DataStore" => "D",
        "Attribute" => "A",
        "Entity" => "Y",
        "Note" => "N",
        "Rule" => "R",
        "Convention" => "C",
        "Bug" => "B",
        "Decision" => "Z",
        "OpenQuestion" => "O",
        "Claim" => "Q",
        "Insight" => "W",
        "Reference" => "M",
        "Term" => "T",
        "Status" => "S",
        "Doubt" => "L",
        _ => node_type,
    }
}

fn code_to_node_type(code: &str) -> &str {
    match code {
        "F" => "Feature",
        "K" => "Concept",
        "I" => "Interface",
        "P" => "Process",
        "D" => "DataStore",
        "A" => "Attribute",
        "Y" => "Entity",
        "N" => "Note",
        "R" => "Rule",
        "C" => "Convention",
        "B" => "Bug",
        "Z" => "Decision",
        "O" => "OpenQuestion",
        "Q" => "Claim",
        "W" => "Insight",
        "M" => "Reference",
        "T" => "Term",
        "S" => "Status",
        "L" => "Doubt",
        _ => code,
    }
}

fn relation_to_code(relation: &str) -> &str {
    match relation {
        "DOCUMENTED_IN" | "DOCUMENTS" => "D",
        "HAS" => "H",
        "TRIGGERS" => "T",
        "AFFECTED_BY" | "AFFECTS" => "A",
        "READS_FROM" | "READS" => "R",
        "GOVERNED_BY" | "GOVERNS" => "G",
        "DEPENDS_ON" => "O",
        "AVAILABLE_IN" => "I",
        "SUPPORTS" => "S",
        "SUMMARIZES" => "U",
        "RELATED_TO" => "L",
        "CONTRADICTS" => "V",
        "CREATED_BY" | "CREATES" => "C",
        _ => relation,
    }
}

fn code_to_relation(code: &str) -> &str {
    match code {
        "D" => "DOCUMENTED_IN",
        "H" => "HAS",
        "T" => "TRIGGERS",
        "A" => "AFFECTED_BY",
        "R" => "READS_FROM",
        "G" => "GOVERNED_BY",
        "O" => "DEPENDS_ON",
        "I" => "AVAILABLE_IN",
        "S" => "SUPPORTS",
        "U" => "SUMMARIZES",
        "L" => "RELATED_TO",
        "V" => "CONTRADICTS",
        "C" => "CREATED_BY",
        _ => code,
    }
}

fn sort_case_insensitive(values: &[String]) -> Vec<String> {
    let mut sorted = values.to_vec();
    sorted.sort_by(|a, b| {
        let la = a.to_ascii_lowercase();
        let lb = b.to_ascii_lowercase();
        la.cmp(&lb).then_with(|| a.cmp(b))
    });
    sorted
}

fn normalize_text(value: &str) -> String {
    value.split_whitespace().collect::<Vec<_>>().join(" ")
}

fn dedupe_case_insensitive(values: Vec<String>) -> Vec<String> {
    let mut seen = std::collections::HashSet::new();
    let mut out = Vec::new();
    for value in values {
        let key = value.to_ascii_lowercase();
        if seen.insert(key) {
            out.push(value);
        }
    }
    out
}

fn parse_utc_timestamp(value: &str) -> bool {
    if value.len() != 20 {
        return false;
    }
    let bytes = value.as_bytes();
    let is_digit = |idx: usize| bytes.get(idx).is_some_and(|b| b.is_ascii_digit());
    if !(is_digit(0)
        && is_digit(1)
        && is_digit(2)
        && is_digit(3)
        && bytes.get(4) == Some(&b'-')
        && is_digit(5)
        && is_digit(6)
        && bytes.get(7) == Some(&b'-')
        && is_digit(8)
        && is_digit(9)
        && bytes.get(10) == Some(&b'T')
        && is_digit(11)
        && is_digit(12)
        && bytes.get(13) == Some(&b':')
        && is_digit(14)
        && is_digit(15)
        && bytes.get(16) == Some(&b':')
        && is_digit(17)
        && is_digit(18)
        && bytes.get(19) == Some(&b'Z'))
    {
        return false;
    }

    let month = value[5..7].parse::<u32>().ok();
    let day = value[8..10].parse::<u32>().ok();
    let hour = value[11..13].parse::<u32>().ok();
    let minute = value[14..16].parse::<u32>().ok();
    let second = value[17..19].parse::<u32>().ok();
    matches!(month, Some(1..=12))
        && matches!(day, Some(1..=31))
        && matches!(hour, Some(0..=23))
        && matches!(minute, Some(0..=59))
        && matches!(second, Some(0..=59))
}

fn strict_kg_mode() -> bool {
    let Ok(value) = std::env::var("KG_STRICT_FORMAT") else {
        return false;
    };
    matches!(
        value.trim().to_ascii_lowercase().as_str(),
        "1" | "true" | "yes" | "on"
    )
}

fn validate_len(
    line_no: usize,
    field: &str,
    value: &str,
    min: usize,
    max: usize,
    strict: bool,
) -> Result<()> {
    let len = value.chars().count();
    if strict && (len < min || len > max) {
        return Err(anyhow::anyhow!(
            "invalid {field} length at line {line_no}: expected {min}..={max}, got {len}"
        ));
    }
    Ok(())
}

fn enforce_field_order(
    line_no: usize,
    key: &str,
    rank: u8,
    last_rank: &mut u8,
    section: &str,
    strict: bool,
) -> Result<()> {
    if strict && rank < *last_rank {
        return Err(anyhow::anyhow!(
            "invalid field order at line {line_no}: {key} in {section} block"
        ));
    }
    if rank > *last_rank {
        *last_rank = rank;
    }
    Ok(())
}

fn field_value<'a>(line: &'a str, key: &str) -> Option<&'a str> {
    if line == key {
        Some("")
    } else {
        line.strip_prefix(key)
            .and_then(|rest| rest.strip_prefix(' '))
    }
}

fn parse_kg(raw: &str, graph_name: &str, strict: bool) -> Result<GraphFile> {
    let mut graph = GraphFile::new(graph_name);
    let mut current_node: Option<Node> = None;
    let mut current_note: Option<Note> = None;
    let mut current_edge_index: Option<usize> = None;
    let mut last_node_rank: u8 = 0;
    let mut last_note_rank: u8 = 0;
    let mut last_edge_rank: u8 = 0;

    for (idx, line) in raw.lines().enumerate() {
        let line_no = idx + 1;
        let trimmed = line.trim();
        if trimmed.is_empty() || trimmed.starts_with('#') {
            continue;
        }

        if let Some(rest) = trimmed.strip_prefix("@ ") {
            if let Some(note) = current_note.take() {
                graph.notes.push(note);
            }
            if let Some(node) = current_node.take() {
                graph.nodes.push(node);
            }
            let (type_code, node_id) = rest.split_once(':').ok_or_else(|| {
                anyhow::anyhow!("invalid node header at line {line_no}: {trimmed}")
            })?;
            current_node = Some(Node {
                id: node_id.trim().to_owned(),
                r#type: code_to_node_type(type_code.trim()).to_owned(),
                name: String::new(),
                properties: NodeProperties::default(),
                source_files: Vec::new(),
            });
            current_edge_index = None;
            last_node_rank = 0;
            last_edge_rank = 0;
            continue;
        }

        if let Some(rest) = trimmed.strip_prefix("! ") {
            if let Some(node) = current_node.take() {
                graph.nodes.push(node);
            }
            if let Some(note) = current_note.take() {
                graph.notes.push(note);
            }
            let mut parts = rest.split_whitespace();
            let id = parts.next().ok_or_else(|| {
                anyhow::anyhow!("invalid note header at line {line_no}: {trimmed}")
            })?;
            let node_id = parts.next().ok_or_else(|| {
                anyhow::anyhow!("invalid note header at line {line_no}: {trimmed}")
            })?;
            current_note = Some(Note {
                id: id.to_owned(),
                node_id: node_id.to_owned(),
                ..Default::default()
            });
            current_edge_index = None;
            last_note_rank = 0;
            continue;
        }

        if let Some(note) = current_note.as_mut() {
            if let Some(rest) = field_value(trimmed, "b") {
                enforce_field_order(line_no, "b", 1, &mut last_note_rank, "note", strict)?;
                note.body = normalize_text(rest.trim());
                continue;
            }
            if let Some(rest) = field_value(trimmed, "t") {
                enforce_field_order(line_no, "t", 2, &mut last_note_rank, "note", strict)?;
                let value = normalize_text(rest.trim());
                if !value.is_empty() {
                    note.tags.push(value);
                }
                continue;
            }
            if let Some(rest) = field_value(trimmed, "a") {
                enforce_field_order(line_no, "a", 3, &mut last_note_rank, "note", strict)?;
                note.author = normalize_text(rest.trim());
                continue;
            }
            if let Some(rest) = field_value(trimmed, "e") {
                enforce_field_order(line_no, "e", 4, &mut last_note_rank, "note", strict)?;
                note.created_at = rest.trim().to_owned();
                continue;
            }
            if let Some(rest) = field_value(trimmed, "p") {
                enforce_field_order(line_no, "p", 5, &mut last_note_rank, "note", strict)?;
                note.provenance = normalize_text(rest.trim());
                continue;
            }
            if let Some(rest) = field_value(trimmed, "s") {
                enforce_field_order(line_no, "s", 6, &mut last_note_rank, "note", strict)?;
                let value = normalize_text(rest.trim());
                if !value.is_empty() {
                    note.source_files.push(value);
                }
                continue;
            }
            return Err(anyhow::anyhow!(
                "unrecognized note line at {line_no}: {trimmed}"
            ));
        }

        let Some(node) = current_node.as_mut() else {
            return Err(anyhow::anyhow!(
                "unexpected line before first node at line {line_no}: {trimmed}"
            ));
        };

        if let Some(rest) = field_value(trimmed, "N") {
            enforce_field_order(line_no, "N", 1, &mut last_node_rank, "node", strict)?;
            let value = normalize_text(rest.trim());
            validate_len(line_no, "N", &value, 1, 120, strict)?;
            node.name = value;
            continue;
        }
        if let Some(rest) = field_value(trimmed, "D") {
            enforce_field_order(line_no, "D", 2, &mut last_node_rank, "node", strict)?;
            let value = normalize_text(rest.trim());
            validate_len(line_no, "D", &value, 1, 200, strict)?;
            node.properties.description = value;
            continue;
        }
        if let Some(rest) = field_value(trimmed, "A") {
            enforce_field_order(line_no, "A", 3, &mut last_node_rank, "node", strict)?;
            let value = normalize_text(rest.trim());
            validate_len(line_no, "A", &value, 1, 80, strict)?;
            node.properties.alias.push(value);
            continue;
        }
        if let Some(rest) = field_value(trimmed, "F") {
            enforce_field_order(line_no, "F", 4, &mut last_node_rank, "node", strict)?;
            let value = normalize_text(rest.trim());
            validate_len(line_no, "F", &value, 1, 200, strict)?;
            node.properties.key_facts.push(value);
            continue;
        }
        if let Some(rest) = field_value(trimmed, "E") {
            enforce_field_order(line_no, "E", 5, &mut last_node_rank, "node", strict)?;
            let value = rest.trim();
            if !value.is_empty() && !parse_utc_timestamp(value) {
                return Err(anyhow::anyhow!(
                    "invalid E timestamp at line {line_no}: expected YYYY-MM-DDTHH:MM:SSZ"
                ));
            }
            node.properties.created_at = value.to_owned();
            continue;
        }
        if let Some(rest) = field_value(trimmed, "C") {
            enforce_field_order(line_no, "C", 6, &mut last_node_rank, "node", strict)?;
            if !rest.trim().is_empty() {
                node.properties.confidence = rest.trim().parse::<f64>().ok();
            }
            continue;
        }
        if let Some(rest) = field_value(trimmed, "V") {
            enforce_field_order(line_no, "V", 7, &mut last_node_rank, "node", strict)?;
            if let Ok(value) = rest.trim().parse::<u8>() {
                node.properties.importance = value;
            }
            continue;
        }
        if let Some(rest) = field_value(trimmed, "P") {
            enforce_field_order(line_no, "P", 8, &mut last_node_rank, "node", strict)?;
            node.properties.provenance = normalize_text(rest.trim());
            continue;
        }
        if let Some(rest) = field_value(trimmed, "S") {
            enforce_field_order(line_no, "S", 10, &mut last_node_rank, "node", strict)?;
            let value = normalize_text(rest.trim());
            validate_len(line_no, "S", &value, 1, 200, strict)?;
            node.source_files.push(value);
            continue;
        }

        if let Some(rest) = trimmed.strip_prefix("> ") {
            let mut parts = rest.split_whitespace();
            let relation = parts.next().ok_or_else(|| {
                anyhow::anyhow!("missing relation in edge at line {line_no}: {trimmed}")
            })?;
            let target_id = parts.next().ok_or_else(|| {
                anyhow::anyhow!("missing target id in edge at line {line_no}: {trimmed}")
            })?;
            graph.edges.push(Edge {
                source_id: node.id.clone(),
                relation: code_to_relation(relation).to_owned(),
                target_id: target_id.to_owned(),
                properties: EdgeProperties::default(),
            });
            current_edge_index = Some(graph.edges.len() - 1);
            last_edge_rank = 0;
            continue;
        }

        if let Some(rest) = field_value(trimmed, "d") {
            enforce_field_order(line_no, "d", 1, &mut last_edge_rank, "edge", strict)?;
            let edge_idx = current_edge_index.ok_or_else(|| {
                anyhow::anyhow!("edge detail without preceding edge at line {line_no}")
            })?;
            let value = normalize_text(rest.trim());
            validate_len(line_no, "d", &value, 1, 200, strict)?;
            graph.edges[edge_idx].properties.detail = value;
            continue;
        }

        if let Some(rest) = field_value(trimmed, "i") {
            enforce_field_order(line_no, "i", 2, &mut last_edge_rank, "edge", strict)?;
            let edge_idx = current_edge_index.ok_or_else(|| {
                anyhow::anyhow!("edge valid_from without preceding edge at line {line_no}")
            })?;
            let value = rest.trim();
            if !value.is_empty() && !parse_utc_timestamp(value) {
                return Err(anyhow::anyhow!(
                    "invalid i timestamp at line {line_no}: expected YYYY-MM-DDTHH:MM:SSZ"
                ));
            }
            graph.edges[edge_idx].properties.valid_from = value.to_owned();
            continue;
        }

        if let Some(rest) = field_value(trimmed, "x") {
            enforce_field_order(line_no, "x", 3, &mut last_edge_rank, "edge", strict)?;
            let edge_idx = current_edge_index.ok_or_else(|| {
                anyhow::anyhow!("edge valid_to without preceding edge at line {line_no}")
            })?;
            let value = rest.trim();
            if !value.is_empty() && !parse_utc_timestamp(value) {
                return Err(anyhow::anyhow!(
                    "invalid x timestamp at line {line_no}: expected YYYY-MM-DDTHH:MM:SSZ"
                ));
            }
            graph.edges[edge_idx].properties.valid_to = value.to_owned();
            continue;
        }

        if let Some(rest) = field_value(trimmed, "-") {
            let mut parts = rest.trim().splitn(2, char::is_whitespace);
            let key = parts.next().unwrap_or("").trim();
            let value = parts.next().unwrap_or("").trim();
            let is_edge_custom = matches!(
                key,
                "edge_feedback_score" | "edge_feedback_count" | "edge_feedback_last_ts_ms"
            );
            if is_edge_custom {
                enforce_field_order(line_no, "-", 4, &mut last_edge_rank, "edge", strict)?;
            } else {
                enforce_field_order(line_no, "-", 9, &mut last_node_rank, "node", strict)?;
            }
            match key {
                "domain_area" => node.properties.domain_area = value.to_owned(),
                "feedback_score" => {
                    node.properties.feedback_score = value.parse::<f64>().unwrap_or(0.0)
                }
                "feedback_count" => {
                    node.properties.feedback_count = value.parse::<u64>().unwrap_or(0)
                }
                "feedback_last_ts_ms" => {
                    node.properties.feedback_last_ts_ms = value.parse::<u64>().ok()
                }
                "edge_feedback_score" => {
                    if let Some(edge_idx) = current_edge_index {
                        graph.edges[edge_idx].properties.feedback_score =
                            value.parse::<f64>().unwrap_or(0.0);
                    }
                }
                "edge_feedback_count" => {
                    if let Some(edge_idx) = current_edge_index {
                        graph.edges[edge_idx].properties.feedback_count =
                            value.parse::<u64>().unwrap_or(0);
                    }
                }
                "edge_feedback_last_ts_ms" => {
                    if let Some(edge_idx) = current_edge_index {
                        graph.edges[edge_idx].properties.feedback_last_ts_ms =
                            value.parse::<u64>().ok();
                    }
                }
                _ => {}
            }
            continue;
        }

        return Err(anyhow::anyhow!("unrecognized line at {line_no}: {trimmed}"));
    }

    if let Some(node) = current_node.take() {
        graph.nodes.push(node);
    }
    if let Some(note) = current_note.take() {
        graph.notes.push(note);
    }

    for node in &mut graph.nodes {
        node.properties.alias =
            sort_case_insensitive(&dedupe_case_insensitive(node.properties.alias.clone()));
        node.properties.key_facts =
            sort_case_insensitive(&dedupe_case_insensitive(node.properties.key_facts.clone()));
        node.source_files =
            sort_case_insensitive(&dedupe_case_insensitive(node.source_files.clone()));
    }

    graph.edges.sort_by(|a, b| {
        a.source_id
            .cmp(&b.source_id)
            .then_with(|| a.relation.cmp(&b.relation))
            .then_with(|| a.target_id.cmp(&b.target_id))
            .then_with(|| a.properties.detail.cmp(&b.properties.detail))
    });

    for note in &mut graph.notes {
        note.tags = sort_case_insensitive(&dedupe_case_insensitive(note.tags.clone()));
        note.source_files =
            sort_case_insensitive(&dedupe_case_insensitive(note.source_files.clone()));
    }
    graph.notes.sort_by(|a, b| {
        a.id.cmp(&b.id)
            .then_with(|| a.node_id.cmp(&b.node_id))
            .then_with(|| a.created_at.cmp(&b.created_at))
    });

    graph.refresh_counts();
    Ok(graph)
}

fn serialize_kg(graph: &GraphFile) -> String {
    let mut out = String::new();
    let mut nodes = graph.nodes.clone();
    nodes.sort_by(|a, b| a.id.cmp(&b.id));

    for node in nodes {
        out.push_str(&format!(
            "@ {}:{}\n",
            node_type_to_code(&node.r#type),
            node.id
        ));
        out.push_str(&format!("N {}\n", node.name));
        out.push_str(&format!("D {}\n", node.properties.description));

        for alias in sort_case_insensitive(&node.properties.alias) {
            out.push_str(&format!("A {}\n", alias));
        }
        for fact in sort_case_insensitive(&node.properties.key_facts) {
            out.push_str(&format!("F {}\n", fact));
        }

        if !node.properties.created_at.is_empty() {
            out.push_str(&format!("E {}\n", node.properties.created_at));
        }
        if let Some(confidence) = node.properties.confidence {
            out.push_str(&format!("C {}\n", confidence));
        }
        out.push_str(&format!("V {}\n", node.properties.importance));
        if !node.properties.provenance.is_empty() {
            out.push_str(&format!("P {}\n", node.properties.provenance));
        }
        if !node.properties.domain_area.is_empty() {
            out.push_str(&format!("- domain_area {}\n", node.properties.domain_area));
        }
        if node.properties.feedback_score != 0.0 {
            out.push_str(&format!(
                "- feedback_score {}\n",
                node.properties.feedback_score
            ));
        }
        if node.properties.feedback_count != 0 {
            out.push_str(&format!(
                "- feedback_count {}\n",
                node.properties.feedback_count
            ));
        }
        if let Some(ts) = node.properties.feedback_last_ts_ms {
            out.push_str(&format!("- feedback_last_ts_ms {}\n", ts));
        }

        for source in sort_case_insensitive(&node.source_files) {
            out.push_str(&format!("S {}\n", source));
        }

        let mut edges: Vec<Edge> = graph
            .edges
            .iter()
            .filter(|edge| edge.source_id == node.id)
            .cloned()
            .collect();
        edges.sort_by(|a, b| {
            a.relation
                .cmp(&b.relation)
                .then_with(|| a.target_id.cmp(&b.target_id))
                .then_with(|| a.properties.detail.cmp(&b.properties.detail))
        });

        for edge in edges {
            out.push_str(&format!(
                "> {} {}\n",
                relation_to_code(&edge.relation),
                edge.target_id
            ));
            if !edge.properties.detail.is_empty() {
                out.push_str(&format!("d {}\n", edge.properties.detail));
            }
            if !edge.properties.valid_from.is_empty() {
                out.push_str(&format!("i {}\n", edge.properties.valid_from));
            }
            if !edge.properties.valid_to.is_empty() {
                out.push_str(&format!("x {}\n", edge.properties.valid_to));
            }
            if edge.properties.feedback_score != 0.0 {
                out.push_str(&format!(
                    "- edge_feedback_score {}\n",
                    edge.properties.feedback_score
                ));
            }
            if edge.properties.feedback_count != 0 {
                out.push_str(&format!(
                    "- edge_feedback_count {}\n",
                    edge.properties.feedback_count
                ));
            }
            if let Some(ts) = edge.properties.feedback_last_ts_ms {
                out.push_str(&format!("- edge_feedback_last_ts_ms {}\n", ts));
            }
        }

        out.push('\n');
    }

    let mut notes = graph.notes.clone();
    notes.sort_by(|a, b| {
        a.id.cmp(&b.id)
            .then_with(|| a.node_id.cmp(&b.node_id))
            .then_with(|| a.created_at.cmp(&b.created_at))
    });
    for note in notes {
        out.push_str(&format!("! {} {}\n", note.id, note.node_id));
        out.push_str(&format!("b {}\n", note.body));
        for tag in sort_case_insensitive(&note.tags) {
            out.push_str(&format!("t {}\n", tag));
        }
        if !note.author.is_empty() {
            out.push_str(&format!("a {}\n", note.author));
        }
        if !note.created_at.is_empty() {
            out.push_str(&format!("e {}\n", note.created_at));
        }
        if !note.provenance.is_empty() {
            out.push_str(&format!("p {}\n", note.provenance));
        }
        for source in sort_case_insensitive(&note.source_files) {
            out.push_str(&format!("s {}\n", source));
        }
        out.push('\n');
    }

    out
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct GraphFile {
    pub metadata: Metadata,
    #[serde(default)]
    pub nodes: Vec<Node>,
    #[serde(default)]
    pub edges: Vec<Edge>,
    #[serde(default)]
    pub notes: Vec<Note>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Metadata {
    pub name: String,
    pub version: String,
    pub description: String,
    pub node_count: usize,
    pub edge_count: usize,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Node {
    pub id: String,
    #[serde(rename = "type")]
    pub r#type: String,
    pub name: String,
    #[serde(default)]
    pub properties: NodeProperties,
    #[serde(default)]
    pub source_files: Vec<String>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct NodeProperties {
    #[serde(default)]
    pub description: String,
    #[serde(default)]
    pub domain_area: String,
    #[serde(default)]
    pub provenance: String,
    #[serde(default)]
    pub confidence: Option<f64>,
    #[serde(default)]
    pub created_at: String,
    #[serde(default = "default_importance")]
    pub importance: u8,
    #[serde(default)]
    pub key_facts: Vec<String>,
    #[serde(default)]
    pub alias: Vec<String>,
    #[serde(default)]
    pub feedback_score: f64,
    #[serde(default)]
    pub feedback_count: u64,
    #[serde(default)]
    pub feedback_last_ts_ms: Option<u64>,
}

fn default_importance() -> u8 {
    4
}

impl Default for NodeProperties {
    fn default() -> Self {
        Self {
            description: String::new(),
            domain_area: String::new(),
            provenance: String::new(),
            confidence: None,
            created_at: String::new(),
            importance: default_importance(),
            key_facts: Vec::new(),
            alias: Vec::new(),
            feedback_score: 0.0,
            feedback_count: 0,
            feedback_last_ts_ms: None,
        }
    }
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Edge {
    pub source_id: String,
    pub relation: String,
    pub target_id: String,
    #[serde(default)]
    pub properties: EdgeProperties,
}

#[derive(Debug, Clone, Default, Serialize, Deserialize)]
pub struct EdgeProperties {
    #[serde(default)]
    pub detail: String,
    #[serde(default)]
    pub valid_from: String,
    #[serde(default)]
    pub valid_to: String,
    #[serde(default)]
    pub feedback_score: f64,
    #[serde(default)]
    pub feedback_count: u64,
    #[serde(default)]
    pub feedback_last_ts_ms: Option<u64>,
}

#[derive(Debug, Clone, Default, Serialize, Deserialize)]
pub struct Note {
    pub id: String,
    pub node_id: String,
    #[serde(default)]
    pub body: String,
    #[serde(default)]
    pub tags: Vec<String>,
    #[serde(default)]
    pub author: String,
    #[serde(default)]
    pub created_at: String,
    #[serde(default)]
    pub provenance: String,
    #[serde(default)]
    pub source_files: Vec<String>,
}

impl GraphFile {
    pub fn new(name: &str) -> Self {
        Self {
            metadata: Metadata {
                name: name.to_owned(),
                version: "1.0".to_owned(),
                description: format!("Knowledge graph: {name}"),
                node_count: 0,
                edge_count: 0,
            },
            nodes: Vec::new(),
            edges: Vec::new(),
            notes: Vec::new(),
        }
    }

    pub fn load(path: &Path) -> Result<Self> {
        let raw = fs::read_to_string(path)
            .with_context(|| format!("failed to read graph: {}", path.display()))?;
        let ext = path
            .extension()
            .and_then(|ext| ext.to_str())
            .unwrap_or("json");
        let mut graph = if ext == "kg" {
            if raw.trim_start().starts_with('{') {
                serde_json::from_str(&raw).with_context(|| {
                    format!(
                        "invalid legacy JSON payload in .kg file: {}",
                        path.display()
                    )
                })?
            } else {
                let graph_name = path
                    .file_stem()
                    .and_then(|stem| stem.to_str())
                    .unwrap_or("graph");
                parse_kg(&raw, graph_name, strict_kg_mode())?
            }
        } else {
            serde_json::from_str(&raw)
                .with_context(|| format!("invalid JSON: {}", path.display()))?
        };
        graph.refresh_counts();
        Ok(graph)
    }

    pub fn save(&self, path: &Path) -> Result<()> {
        let mut graph = self.clone();
        graph.refresh_counts();
        let ext = path
            .extension()
            .and_then(|ext| ext.to_str())
            .unwrap_or("json");
        let raw = if ext == "kg" {
            serialize_kg(&graph)
        } else {
            serde_json::to_string_pretty(&graph).context("failed to serialize graph")?
        };
        atomic_write(path, &raw)?;
        backup_graph_if_stale(path, &raw)
    }

    pub fn refresh_counts(&mut self) {
        self.metadata.node_count = self.nodes.len();
        self.metadata.edge_count = self.edges.len();
    }

    pub fn node_by_id(&self, id: &str) -> Option<&Node> {
        self.nodes.iter().find(|node| node.id == id)
    }

    pub fn node_by_id_sorted(&self, id: &str) -> Option<&Node> {
        self.nodes
            .binary_search_by(|node| node.id.as_str().cmp(id))
            .ok()
            .and_then(|idx| self.nodes.get(idx))
    }

    pub fn node_by_id_mut(&mut self, id: &str) -> Option<&mut Node> {
        self.nodes.iter_mut().find(|node| node.id == id)
    }

    pub fn has_edge(&self, source_id: &str, relation: &str, target_id: &str) -> bool {
        self.edges.iter().any(|edge| {
            edge.source_id == source_id && edge.relation == relation && edge.target_id == target_id
        })
    }
}

#[cfg(test)]
mod tests {
    use super::{GraphFile, parse_kg};

    #[test]
    fn save_and_load_kg_roundtrip_keeps_core_fields() {
        let dir = tempfile::tempdir().expect("temp dir");
        let path = dir.path().join("graph.kg");

        let mut graph = GraphFile::new("graph");
        graph.nodes.push(crate::Node {
            id: "concept:refrigerator".to_owned(),
            r#type: "Concept".to_owned(),
            name: "Lodowka".to_owned(),
            properties: crate::NodeProperties {
                description: "Urzadzenie chlodzace".to_owned(),
                provenance: "U".to_owned(),
                created_at: "2026-04-04T12:00:00Z".to_owned(),
                importance: 5,
                key_facts: vec!["A".to_owned(), "b".to_owned()],
                alias: vec!["Fridge".to_owned()],
                ..Default::default()
            },
            source_files: vec!["docs/fridge.md".to_owned()],
        });
        graph.edges.push(crate::Edge {
            source_id: "concept:refrigerator".to_owned(),
            relation: "READS_FROM".to_owned(),
            target_id: "datastore:settings".to_owned(),
            properties: crate::EdgeProperties {
                detail: "runtime read".to_owned(),
                valid_from: "2026-04-04T12:00:00Z".to_owned(),
                valid_to: "2026-04-05T12:00:00Z".to_owned(),
                ..Default::default()
            },
        });

        graph.save(&path).expect("save kg");
        let raw = std::fs::read_to_string(&path).expect("read kg");
        assert!(raw.contains("@ K:concept:refrigerator"));
        assert!(raw.contains("> R datastore:settings"));

        let loaded = GraphFile::load(&path).expect("load kg");
        assert_eq!(loaded.nodes.len(), 1);
        assert_eq!(loaded.edges.len(), 1);
        let node = &loaded.nodes[0];
        assert_eq!(node.properties.importance, 5);
        assert_eq!(node.properties.provenance, "U");
        assert_eq!(node.name, "Lodowka");
        assert_eq!(loaded.edges[0].relation, "READS_FROM");
        assert_eq!(loaded.edges[0].properties.detail, "runtime read");
        assert_eq!(
            loaded.edges[0].properties.valid_from,
            "2026-04-04T12:00:00Z"
        );
        assert_eq!(loaded.edges[0].properties.valid_to, "2026-04-05T12:00:00Z");
    }

    #[test]
    fn load_supports_legacy_json_payload_with_kg_extension() {
        let dir = tempfile::tempdir().expect("temp dir");
        let path = dir.path().join("legacy.kg");
        std::fs::write(
            &path,
            r#"{
  "metadata": {"name": "legacy", "version": "1.0", "description": "x", "node_count": 0, "edge_count": 0},
  "nodes": [],
  "edges": [],
  "notes": []
}"#,
        )
        .expect("write legacy payload");

        let loaded = GraphFile::load(&path).expect("load legacy kg");
        assert_eq!(loaded.metadata.name, "legacy");
        assert!(loaded.nodes.is_empty());
    }

    #[test]
    fn load_kg_rejects_invalid_timestamp_format() {
        let dir = tempfile::tempdir().expect("temp dir");
        let path = dir.path().join("invalid-ts.kg");
        std::fs::write(
            &path,
            "@ K:concept:x\nN X\nD Desc\nE 2026-04-04 12:00:00\nV 4\nP U\n",
        )
        .expect("write kg");

        let err = GraphFile::load(&path).expect_err("invalid timestamp should fail");
        let msg = format!("{err:#}");
        assert!(msg.contains("invalid E timestamp"));
    }

    #[test]
    fn load_kg_rejects_invalid_edge_timestamp_format() {
        let dir = tempfile::tempdir().expect("temp dir");
        let path = dir.path().join("invalid-edge-ts.kg");
        std::fs::write(
            &path,
            "@ K:concept:x\nN X\nD Desc\nE 2026-04-04T12:00:00Z\nV 4\nP U\nS docs/a.md\n> H concept:y\ni 2026-04-04 12:00:00\n",
        )
        .expect("write kg");

        let err = GraphFile::load(&path).expect_err("invalid edge timestamp should fail");
        let msg = format!("{err:#}");
        assert!(msg.contains("invalid i timestamp"));
    }

    #[test]
    fn load_kg_normalizes_and_dedupes_multivalue_fields() {
        let dir = tempfile::tempdir().expect("temp dir");
        let path = dir.path().join("normalize.kg");
        std::fs::write(
            &path,
            "@ K:concept:x\nN  Name   With   Spaces \nD  Desc   with   spaces \nA Alias\nA alias\nF fact one\nF FACT   one\nS docs/a.md\nS docs/a.md\nE 2026-04-04T12:00:00Z\nV 4\nP U\n",
        )
        .expect("write kg");

        let loaded = GraphFile::load(&path).expect("load kg");
        let node = &loaded.nodes[0];
        assert_eq!(node.name, "Name With Spaces");
        assert_eq!(node.properties.description, "Desc with spaces");
        assert_eq!(node.properties.alias.len(), 1);
        assert_eq!(node.properties.key_facts.len(), 1);
        assert_eq!(node.source_files.len(), 1);
    }

    #[test]
    fn save_and_load_kg_roundtrip_keeps_notes_without_json_fallback() {
        let dir = tempfile::tempdir().expect("temp dir");
        let path = dir.path().join("graph-notes.kg");

        let mut graph = GraphFile::new("graph-notes");
        graph.nodes.push(crate::Node {
            id: "concept:refrigerator".to_owned(),
            r#type: "Concept".to_owned(),
            name: "Lodowka".to_owned(),
            properties: crate::NodeProperties {
                description: "Urzadzenie chlodzace".to_owned(),
                provenance: "U".to_owned(),
                created_at: "2026-04-04T12:00:00Z".to_owned(),
                ..Default::default()
            },
            source_files: vec!["docs/fridge.md".to_owned()],
        });
        graph.notes.push(crate::Note {
            id: "note:1".to_owned(),
            node_id: "concept:refrigerator".to_owned(),
            body: "Important maintenance insight".to_owned(),
            tags: vec!["Maintenance".to_owned(), "maintenance".to_owned()],
            author: "alice".to_owned(),
            created_at: "1712345678".to_owned(),
            provenance: "U".to_owned(),
            source_files: vec!["docs/a.md".to_owned(), "docs/a.md".to_owned()],
        });

        graph.save(&path).expect("save kg");
        let raw = std::fs::read_to_string(&path).expect("read kg");
        assert!(raw.contains("! note:1 concept:refrigerator"));
        assert!(!raw.trim_start().starts_with('{'));

        let loaded = GraphFile::load(&path).expect("load kg");
        assert_eq!(loaded.notes.len(), 1);
        let note = &loaded.notes[0];
        assert_eq!(note.id, "note:1");
        assert_eq!(note.node_id, "concept:refrigerator");
        assert_eq!(note.body, "Important maintenance insight");
        assert_eq!(note.tags.len(), 1);
        assert_eq!(note.source_files.len(), 1);
    }

    #[test]
    fn strict_mode_rejects_out_of_order_node_fields() {
        let raw = "@ K:concept:x\nD Desc\nN Name\nE 2026-04-04T12:00:00Z\nV 4\nP U\nS docs/a.md\n";
        let err = parse_kg(raw, "x", true).expect_err("strict mode should fail on field order");
        assert!(format!("{err:#}").contains("invalid field order"));
    }

    #[test]
    fn strict_mode_rejects_overlong_name_but_compat_mode_allows_it() {
        let long_name = "N ".to_owned() + &"X".repeat(121);
        let raw = format!(
            "@ K:concept:x\n{}\nD Desc\nE 2026-04-04T12:00:00Z\nV 4\nP U\nS docs/a.md\n",
            long_name
        );

        let strict_err = parse_kg(&raw, "x", true).expect_err("strict mode should fail on length");
        assert!(format!("{strict_err:#}").contains("invalid N length"));

        parse_kg(&raw, "x", false).expect("compat mode keeps permissive behavior");
    }

    #[test]
    fn save_kg_skips_empty_e_and_p_fields() {
        let dir = tempfile::tempdir().expect("temp dir");
        let path = dir.path().join("no-empty-ep.kg");

        let mut graph = GraphFile::new("graph");
        graph.nodes.push(crate::Node {
            id: "concept:x".to_owned(),
            r#type: "Concept".to_owned(),
            name: "X".to_owned(),
            properties: crate::NodeProperties {
                description: "Desc".to_owned(),
                provenance: String::new(),
                created_at: String::new(),
                ..Default::default()
            },
            source_files: vec!["docs/a.md".to_owned()],
        });

        graph.save(&path).expect("save kg");
        let raw = std::fs::read_to_string(&path).expect("read kg");
        assert!(!raw.contains("\nE \n"));
        assert!(!raw.contains("\nP \n"));
    }
}