rbt_weave

use std::collections::HashSet;

use crate::parser::{ParseError, SourceEntry};

/// Maximum relationships per file.
const MAX_RELATIONSHIPS_PER_FILE: usize = 500;

/// All known relationship types, organized by category per ADR-014 §3.
const KNOWN_REL_TYPES: &[&str] = &[
    // Organizational
    "employed_by",
    "member_of",
    "leads",
    "founded",
    "owns",
    "subsidiary_of",
    // Legal/Criminal
    "charged_with",
    "convicted_of",
    "investigated_by",
    "prosecuted_by",
    "defended_by",
    "testified_in",
    "sentenced_to",
    "appealed",
    "acquitted_of",
    "pardoned_by",
    "arrested_by",
    // Financial
    "paid_to",
    "received_from",
    "funded_by",
    "awarded_contract",
    "approved_budget",
    "seized_from",
    // Governance
    "appointed_by",
    "approved_by",
    "regulated_by",
    "licensed_by",
    "lobbied",
    // Personal
    "family_of",
    "associate_of",
    // Temporal
    "preceded_by",
    // Document
    "documents",
    "authorizes",
    "references",
    // Case
    "related_to",
    "part_of",
    "involved_in",
    // Source
    "sourced_by",
];

/// Known fields on relationships (nested bullets).
const REL_FIELDS: &[&str] = &[
    "id",
    "source",
    "description",
    "amounts",
    "valid_from",
    "valid_until",
];

/// A parsed relationship.
#[derive(Debug)]
pub struct Rel {
    pub source_name: String,
    pub target_name: String,
    pub rel_type: String,
    pub source_urls: Vec<String>,
    pub fields: Vec<(String, String)>,
    /// Stored NULID from `id:` field (None if not yet generated).
    pub id: Option<String>,
    /// Line number (1-indexed) in the original file.
    pub line: usize,
}

/// Parse relationships from the `## Relationships` section body.
///
/// `entity_names` is the set of entity names defined in the file (for resolution).
/// `default_sources` are the front matter sources used when no `source:` override.
#[allow(clippy::too_many_lines)]
pub fn parse_relationships(
    body: &str,
    section_start_line: usize,
    entity_names: &HashSet<&str>,
    default_sources: &[SourceEntry],
    errors: &mut Vec<ParseError>,
) -> Vec<Rel> {
    let lines: Vec<&str> = body.lines().collect();
    let mut rels: Vec<Rel> = Vec::new();

    // Current relationship being built
    let mut current: Option<RelBuilder> = None;

    for (i, line) in lines.iter().enumerate() {
        let file_line = section_start_line + 1 + i;
        let trimmed = line.trim();

        // Top-level bullet: `- Source -> Target: type`
        if trimmed.starts_with("- ") && !line.starts_with("  ") {
            // Flush previous
            if let Some(builder) = current.take() {
                rels.push(builder.finish(default_sources));
            }

            let item = &trimmed[2..];
            match parse_rel_line(item) {
                Some((source, target, rel_type)) => {
                    // Validate rel_type
                    if !KNOWN_REL_TYPES.contains(&rel_type.as_str()) {
                        errors.push(ParseError {
                            line: file_line,
                            message: format!(
                                "unknown relationship type {rel_type:?} (known: {})",
                                KNOWN_REL_TYPES.join(", ")
                            ),
                        });
                    }

                    // Validate entity names
                    if !entity_names.contains(&source.as_str()) {
                        errors.push(ParseError {
                            line: file_line,
                            message: format!(
                                "entity {source:?} in relationship not defined in file"
                            ),
                        });
                    }
                    if !entity_names.contains(&target.as_str()) {
                        errors.push(ParseError {
                            line: file_line,
                            message: format!(
                                "entity {target:?} in relationship not defined in file"
                            ),
                        });
                    }

                    current = Some(RelBuilder {
                        source_name: source,
                        target_name: target,
                        rel_type,
                        source_urls: Vec::new(),
                        fields: Vec::new(),
                        id: None,
                        line: file_line,
                    });
                }
                None => {
                    errors.push(ParseError {
                        line: file_line,
                        message: format!(
                            "invalid relationship syntax: expected `- Source -> Target: type`, got {trimmed:?}"
                        ),
                    });
                }
            }
            continue;
        }

        // Indented field: `  key: value`
        if line.starts_with("  ") && current.is_some() {
            if let Some((key, value)) = parse_kv(trimmed) {
                if !REL_FIELDS.contains(&key.as_str()) {
                    errors.push(ParseError {
                        line: file_line,
                        message: format!("unknown relationship field {key:?}"),
                    });
                    continue;
                }

                let builder = current.as_mut().unwrap_or_else(|| unreachable!());

                if key == "id" {
                    builder.id = Some(value);
                } else if key == "source" {
                    if !value.starts_with("https://") {
                        errors.push(ParseError {
                            line: file_line,
                            message: format!("relationship source URL must be HTTPS: {value:?}"),
                        });
                    }
                    if builder.source_urls.contains(&value) {
                        errors.push(ParseError {
                            line: file_line,
                            message: format!("duplicate relationship source url: {value:?}"),
                        });
                    }
                    builder.source_urls.push(value);
                } else {
                    // Validate field constraints
                    validate_rel_field(&key, &value, file_line, errors);
                    builder.fields.push((key, value));
                }
            } else {
                errors.push(ParseError {
                    line: file_line,
                    message: format!(
                        "invalid field syntax: expected `key: value`, got {trimmed:?}"
                    ),
                });
            }
        }

        // Ignore blank lines
    }

    // Flush last
    if let Some(builder) = current.take() {
        rels.push(builder.finish(default_sources));
    }

    // Boundary check
    if rels.len() > MAX_RELATIONSHIPS_PER_FILE {
        errors.push(ParseError {
            line: section_start_line,
            message: format!(
                "too many relationships (max {MAX_RELATIONSHIPS_PER_FILE}, got {})",
                rels.len()
            ),
        });
    }

    rels
}

struct RelBuilder {
    source_name: String,
    target_name: String,
    rel_type: String,
    source_urls: Vec<String>,
    fields: Vec<(String, String)>,
    id: Option<String>,
    line: usize,
}

impl RelBuilder {
    fn finish(self, default_sources: &[SourceEntry]) -> Rel {
        let source_urls = if self.source_urls.is_empty() {
            default_sources
                .iter()
                .map(|s| s.url().to_string())
                .collect()
        } else {
            self.source_urls
        };

        Rel {
            source_name: self.source_name,
            target_name: self.target_name,
            rel_type: self.rel_type,
            source_urls,
            fields: self.fields,
            id: self.id,
            line: self.line,
        }
    }
}

/// Parse `Source -> Target: type` from a relationship bullet.
fn parse_rel_line(item: &str) -> Option<(String, String, String)> {
    let arrow_pos = item.find(" -> ")?;
    let source = item[..arrow_pos].trim();
    let after_arrow = &item[arrow_pos + 4..];

    let colon_pos = after_arrow.rfind(':')?;
    let target = after_arrow[..colon_pos].trim();
    let rel_type = after_arrow[colon_pos + 1..]
        .trim()
        .to_lowercase()
        .replace(' ', "_");

    if source.is_empty() || target.is_empty() || rel_type.is_empty() {
        return None;
    }

    Some((source.to_string(), target.to_string(), rel_type))
}

fn parse_kv(s: &str) -> Option<(String, String)> {
    let colon = s.find(':')?;
    let key = s[..colon].trim();
    if key.is_empty() {
        return None;
    }
    let value = s[colon + 1..].trim();
    Some((key.to_string(), value.to_string()))
}

fn validate_rel_field(key: &str, value: &str, line: usize, errors: &mut Vec<ParseError>) {
    let max = match key {
        "description" => 1000,
        "amounts" => 200,
        "valid_from" | "valid_until" => 10,
        _ => return,
    };

    if value.len() > max {
        errors.push(ParseError {
            line,
            message: format!(
                "relationship field {key:?} exceeds {max} chars (got {})",
                value.len()
            ),
        });
    }

    // Date format validation
    if matches!(key, "valid_from" | "valid_until") && !value.is_empty() {
        let valid = matches!(value.len(), 4 | 7 | 10)
            && value.chars().enumerate().all(|(i, c)| match i {
                4 | 7 => c == '-',
                _ => c.is_ascii_digit(),
            });
        if !valid {
            errors.push(ParseError {
                line,
                message: format!(
                    "relationship field {key:?} must be YYYY, YYYY-MM, or YYYY-MM-DD, got {value:?}"
                ),
            });
        }
    }
}

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

    #[test]
    fn parse_basic_relationship() {
        let body = "\n- Alice -> Bob: employed_by\n";
        let names = HashSet::from(["Alice", "Bob"]);
        let sources = vec![SourceEntry::Url("https://example.com/src".into())];
        let mut errors = Vec::new();

        let rels = parse_relationships(body, 50, &names, &sources, &mut errors);
        assert!(errors.is_empty(), "errors: {errors:?}");
        assert_eq!(rels.len(), 1);
        assert_eq!(rels[0].source_name, "Alice");
        assert_eq!(rels[0].target_name, "Bob");
        assert_eq!(rels[0].rel_type, "employed_by");
        // Should default to front matter sources
        assert_eq!(rels[0].source_urls, vec!["https://example.com/src"]);
    }

    #[test]
    fn parse_relationship_with_source_override() {
        let body = [
            "",
            "- Alice -> Bob: associate_of",
            "  source: https://specific.com/article",
            "",
        ]
        .join("\n");
        let names = HashSet::from(["Alice", "Bob"]);
        let sources = vec![SourceEntry::Url("https://default.com".into())];
        let mut errors = Vec::new();

        let rels = parse_relationships(&body, 10, &names, &sources, &mut errors);
        assert!(errors.is_empty(), "errors: {errors:?}");
        assert_eq!(rels[0].source_urls, vec!["https://specific.com/article"]);
    }

    #[test]
    fn parse_relationship_with_fields() {
        let body = [
            "",
            "- Alice -> Corp: paid_to",
            "  amounts: 50000 EUR",
            "  valid_from: 2020-01",
            "  description: Campaign donation",
            "",
        ]
        .join("\n");
        let names = HashSet::from(["Alice", "Corp"]);
        let mut errors = Vec::new();

        let rels = parse_relationships(&body, 10, &names, &[], &mut errors);
        assert!(errors.is_empty(), "errors: {errors:?}");
        assert_eq!(rels[0].fields.len(), 3);
    }

    #[test]
    fn reject_unknown_rel_type() {
        let body = "\n- Alice -> Bob: best_friends\n";
        let names = HashSet::from(["Alice", "Bob"]);
        let mut errors = Vec::new();

        parse_relationships(body, 1, &names, &[], &mut errors);
        assert!(
            errors
                .iter()
                .any(|e| e.message.contains("unknown relationship type"))
        );
    }

    #[test]
    fn reject_unresolved_entity() {
        let body = "\n- Alice -> Unknown: employed_by\n";
        let names = HashSet::from(["Alice"]);
        let mut errors = Vec::new();

        parse_relationships(body, 1, &names, &[], &mut errors);
        assert!(
            errors
                .iter()
                .any(|e| e.message.contains("not defined in file"))
        );
    }

    #[test]
    fn reject_non_https_source_override() {
        let body = [
            "",
            "- Alice -> Bob: associate_of",
            "  source: http://insecure.com",
            "",
        ]
        .join("\n");
        let names = HashSet::from(["Alice", "Bob"]);
        let mut errors = Vec::new();

        parse_relationships(&body, 1, &names, &[], &mut errors);
        assert!(errors.iter().any(|e| e.message.contains("HTTPS")));
    }

    #[test]
    fn reject_unknown_rel_field() {
        let body = ["", "- Alice -> Bob: associate_of", "  foobar: value", ""].join("\n");
        let names = HashSet::from(["Alice", "Bob"]);
        let mut errors = Vec::new();

        parse_relationships(&body, 1, &names, &[], &mut errors);
        assert!(
            errors
                .iter()
                .any(|e| e.message.contains("unknown relationship field"))
        );
    }

    #[test]
    fn multiple_relationships() {
        let body = [
            "",
            "- Alice -> Bob: employed_by",
            "- Bob -> Corp: member_of",
            "- Corp -> Alice: charged_with",
            "",
        ]
        .join("\n");
        let names = HashSet::from(["Alice", "Bob", "Corp"]);
        let mut errors = Vec::new();

        let rels = parse_relationships(&body, 1, &names, &[], &mut errors);
        assert!(errors.is_empty(), "errors: {errors:?}");
        assert_eq!(rels.len(), 3);
    }

    #[test]
    fn parse_rel_line_syntax() {
        let result = parse_rel_line("Mark Bonnick -> Arsenal FC: employed_by");
        assert_eq!(
            result,
            Some((
                "Mark Bonnick".into(),
                "Arsenal FC".into(),
                "employed_by".into()
            ))
        );
    }

    #[test]
    fn parse_rel_line_invalid() {
        assert!(parse_rel_line("not a relationship").is_none());
        assert!(parse_rel_line("-> Target: type").is_none());
        assert!(parse_rel_line("Source -> : type").is_none());
    }

    #[test]
    fn relationship_date_validation() {
        let body = [
            "",
            "- Alice -> Bob: associate_of",
            "  valid_from: not-a-date",
            "",
        ]
        .join("\n");
        let names = HashSet::from(["Alice", "Bob"]);
        let mut errors = Vec::new();

        parse_relationships(&body, 1, &names, &[], &mut errors);
        assert!(errors.iter().any(|e| e.message.contains("YYYY")));
    }

    #[test]
    fn multiple_source_overrides() {
        let body = [
            "",
            "- Alice -> Bob: associate_of",
            "  source: https://first.com",
            "  source: https://second.com",
            "",
        ]
        .join("\n");
        let names = HashSet::from(["Alice", "Bob"]);
        let mut errors = Vec::new();

        let rels = parse_relationships(&body, 1, &names, &[], &mut errors);
        assert!(errors.is_empty(), "errors: {errors:?}");
        assert_eq!(rels[0].source_urls.len(), 2);
    }
}