//! Agent spec parsing + validation.
//!
//! An agent spec is a markdown file with YAML frontmatter. The required
//! fields mirror the format documented in `CLAUDE.md`. Validation fails fast
//! on missing fields so a broken spec never reaches a runtime.

use anyhow::Result;
use serde::{Deserialize, Serialize};
use std::path::Path;
use thiserror::Error;
use walkdir::WalkDir;

#[derive(Debug, Error)]
pub enum SpecError {
    #[error("missing required field '{0}' in {1}")]
    MissingField(&'static str, String),
    #[error("could not read file {0}: {1}")]
    Io(String, String),
    #[error("could not parse frontmatter in {0}: {1}")]
    Parse(String, String),
}

/// The frontmatter of an agent spec. Mirrors `agents/<dept>/<name>.md`.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct AgentSpec {
    pub name: String,
    pub tier: String,
    pub department: String,
    pub reports_to: String,
    pub autonomy: String,
    #[serde(default)]
    pub skills: Vec<String>,
    #[serde(default)]
    pub tools: Vec<String>,
    #[serde(default)]
    pub forbidden: Vec<String>,
    #[serde(default)]
    pub budget: Budget,
    #[serde(default)]
    pub language: Language,
}

#[derive(Debug, Clone, Serialize, Deserialize, Default)]
pub struct Budget {
    #[serde(default)]
    pub max_eur_per_task: f64,
    #[serde(default)]
    pub max_tokens: u64,
}

#[derive(Debug, Clone, Serialize, Deserialize, Default)]
pub struct Language {
    #[serde(default = "default_chat")]
    pub chat: String,
    #[serde(default = "default_deliverables")]
    pub deliverables: String,
}

fn default_chat() -> String {
    "tr".into()
}
fn default_deliverables() -> String {
    "en".into()
}

const REQUIRED_FIELDS: &[&str] = &["name", "tier", "department", "reports_to", "autonomy"];

/// Walks `agents/` and parses every `.md` into an `AgentSpec`.
///
/// Returns the specs + any validation errors. A spec with errors is excluded
/// from the success list and reported in the error vec.
pub fn validate_agents(root: &Path) -> Result<(Vec<AgentSpec>, Vec<SpecError>)> {
    let mut specs = Vec::new();
    let mut errors = Vec::new();

    for entry in WalkDir::new(root).into_iter().filter_map(|e| e.ok()) {
        let path = entry.path();
        if !path.is_file() || path.extension().and_then(|s| s.to_str()) != Some("md") {
            continue;
        }
        let rel = path.strip_prefix(root).unwrap_or(path).display().to_string();
        let content = match std::fs::read_to_string(path) {
            Ok(c) => c,
            Err(e) => {
                errors.push(SpecError::Io(rel, e.to_string()));
                continue;
            }
        };
        let frontmatter = match extract_frontmatter(&content) {
            Some(fm) => fm,
            None => {
                errors.push(SpecError::Parse(rel, "no --- frontmatter block found".into()));
                continue;
            }
        };
        // Parse the YAML frontmatter as JSON-ish: convert simple YAML to JSON.
        // (Agent frontmatter is flat — key: value + list items — so a minimal
        // conversion suffices without a full YAML parser dep.)
        let json_str = match yaml_to_json(frontmatter) {
            Ok(j) => j,
            Err(e) => {
                errors.push(SpecError::Parse(rel, e.to_string()));
                continue;
            }
        };
        let parsed: serde_json::Value = match serde_json::from_str(&json_str) {
            Ok(v) => v,
            Err(e) => {
                errors.push(SpecError::Parse(rel, e.to_string()));
                continue;
            }
        };
        // Check required fields.
        let obj = match parsed.as_object() {
            Some(o) => o,
            None => {
                errors.push(SpecError::Parse(rel, "frontmatter is not an object".into()));
                continue;
            }
        };
        let mut missing = Vec::new();
        for field in REQUIRED_FIELDS {
            if !obj.contains_key(*field) {
                missing.push(*field);
            }
        }
        if !missing.is_empty() {
            errors.push(SpecError::MissingField(missing[0], rel));
            continue;
        }
        // Deserialize into the typed struct (best-effort; ignore unknown fields).
        let spec: AgentSpec = match serde_json::from_value(parsed) {
            Ok(s) => s,
            Err(e) => {
                errors.push(SpecError::Parse(rel, e.to_string()));
                continue;
            }
        };
        specs.push(spec);
    }

    Ok((specs, errors))
}

/// Extracts the content between `---` fences at the top of a markdown file.
fn extract_frontmatter(content: &str) -> Option<&str> {
    let trimmed = content.trim_start();
    if !trimmed.starts_with("---") {
        return None;
    }
    let after_first_fence = &trimmed[3..];
    let end = after_first_fence.find("\n---")?;
    Some(after_first_fence[..end].trim())
}

/// Minimal YAML→JSON converter for flat agent-spec frontmatter.
///
/// Supports only the subset we use: `key: value`, `key: [a, b, c]` inline
/// arrays, and block arrays (`- item`). Nested objects (like `budget:` with
/// sub-keys) and `language:` are handled with a simple indentation stack.
/// This avoids pulling a full YAML parser dep into the scaffold.
fn yaml_to_json(yaml: &str) -> Result<String> {
    let mut out = String::from("{");
    let lines: Vec<&str> = yaml.lines().collect();
    let mut i = 0;
    while i < lines.len() {
        let line = lines[i].trim_end();
        if line.trim().is_empty() || line.trim_start().starts_with('#') {
            i += 1;
            continue;
        }
        let (key, rest) = match line.split_once(':') {
            Some((k, v)) => (k.trim(), v.trim()),
            None => {
                i += 1;
                continue;
            }
        };
        if rest.is_empty() {
            // Could be a block array (`- item`) or a nested object.
            // Peek ahead: collect comment + dash lines as array items.
            let mut items: Vec<String> = Vec::new();
            let mut j = i + 1;
            while j < lines.len() {
                let l = lines[j].trim();
                if l.is_empty() {
                    j += 1;
                    continue;
                }
                // Skip comment lines inside a block array.
                if l.starts_with('#') {
                    j += 1;
                    continue;
                }
                if !l.starts_with('-') {
                    break;
                }
                let val = l.trim_start_matches('-').trim();
                items.push(quote_or_passthrough(val));
                j += 1;
            }
            if !items.is_empty() {
                out.push_str(&format!("\"{key}\":[{}],", items.join(",")));
                i = j;
                continue;
            }
            // Nested object: collect indented lines until dedent.
            let mut sub = String::from("{");
            while j < lines.len() {
                let l = lines[j];
                if !l.starts_with(' ') && !l.starts_with('\t') {
                    break;
                }
                if let Some((sk, sv)) = l.trim().split_once(':') {
                    sub.push_str(&format!(
                        "\"{}\":{},",
                        sk.trim(),
                        quote_or_passthrough(sv.trim())
                    ));
                }
                j += 1;
            }
            sub.pop(); // trailing comma
            sub.push('}');
            out.push_str(&format!("\"{key}\":{sub},"));
            i = j;
            continue;
        }
        // Inline array? `[a, b, c]`
        if rest.starts_with('[') {
            let inner = rest
                .trim_start_matches('[')
                .trim_end_matches(']')
                .split(',')
                .map(|s| quote_or_passthrough(s.trim()))
                .collect::<Vec<_>>()
                .join(",");
            out.push_str(&format!("\"{key}\":[{inner}],"));
        } else {
            out.push_str(&format!(
                "\"{key}\":{},",
                quote_or_passthrough(rest)
            ));
        }
        i += 1;
    }
    if out.ends_with(',') {
        out.pop();
    }
    out.push('}');
    Ok(out)
}

/// Quotes a value as a JSON string unless it looks like a number or bool.
fn quote_or_passthrough(v: &str) -> String {
    let v = v.trim();
    if v.is_empty() {
        return "\"\"".into();
    }
    if v == "true" || v == "false" || v == "null" {
        return v.into();
    }
    if v.parse::<f64>().is_ok() {
        return v.into();
    }
    // Strip surrounding quotes if present, then re-add as JSON string.
    let v = v.trim_matches('"');
    format!("\"{}\"", v.replace('\\', "\\\\").replace('"', "\\\""))
}