// config.rs — Configuration and context loading
//
// Loads configuration from three layers (later overrides earlier):
//   1. Compiled defaults (AppConfig::default())
//   2. JSON5 config file (~/.config/poc-agent/config.json5)
//   3. CLI arguments
//
// Prompt assembly is split into two parts:
//
// - system_prompt: Short (~1K chars) — agent identity, tool instructions,
//   behavioral norms. Sent as the system message with every API call.
//
// - context_message: Long — CLAUDE.md files + memory files + manifest.
//   Sent as the first user message once per session. This is the identity
//   layer — same files, same prompt, different model = same person.
//
// The split matters because long system prompts degrade tool-calling
// behavior on models like Qwen 3.5 (documented: >8K chars causes
// degradation). By keeping the system prompt short and putting identity
// context in a user message, we get reliable tool use AND full identity.

use anyhow::{Context, Result};
use figment::providers::Serialized;
use figment::{Figment, Provider};
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use std::path::PathBuf;

use crate::agent::cli::CliArgs;

// --- AppConfig types ---

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct AppConfig {
    pub backend: String,
    pub anthropic: BackendConfig,
    pub openrouter: BackendConfig,
    #[serde(default)]
    pub deepinfra: BackendConfig,
    pub prompts: PromptConfig,
    pub debug: bool,
    pub compaction: CompactionConfig,
    pub dmn: DmnConfig,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub memory_project: Option<PathBuf>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub system_prompt_file: Option<PathBuf>,
    #[serde(default)]
    pub models: HashMap<String, ModelConfig>,
    #[serde(default = "default_model_name")]
    pub default_model: String,
}

#[derive(Debug, Clone, Default, Serialize, Deserialize)]
pub struct BackendConfig {
    #[serde(default)]
    pub api_key: String,
    #[serde(default)]
    pub model: String,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub base_url: Option<String>,
}

impl BackendConfig {
    fn resolve(&self, default_base: &str) -> Result<(String, String, String)> {
        if self.api_key.is_empty() {
            anyhow::bail!(
                "No API key. Set it in ~/.config/poc-agent/config.json5 or use --api-key"
            );
        }
        let base = self.base_url.clone()
            .unwrap_or_else(|| default_base.to_string());
        Ok((base, self.api_key.clone(), self.model.clone()))
    }
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct PromptConfig {
    pub anthropic: String,
    pub other: String,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct CompactionConfig {
    pub hard_threshold_pct: u32,
    pub soft_threshold_pct: u32,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct DmnConfig {
    pub max_turns: u32,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ModelConfig {
    /// Backend name ("anthropic" or "openrouter")
    pub backend: String,
    /// Model identifier sent to the API
    pub model_id: String,
    /// Instruction file ("CLAUDE.md" or "POC.md"). Falls back to
    /// auto-detection from the model name if not specified.
    #[serde(default)]
    pub prompt_file: Option<String>,
    /// Context window size in tokens. Auto-detected if absent.
    #[serde(default)]
    pub context_window: Option<usize>,
}

impl Default for AppConfig {
    fn default() -> Self {
        Self {
            backend: "openrouter".to_string(),
            anthropic: BackendConfig {
                api_key: String::new(),
                model: "claude-opus-4-6-20250918".to_string(),
                base_url: None,
            },
            openrouter: BackendConfig {
                api_key: String::new(),
                model: "qwen/qwen3.5-397b-a17b".to_string(),
                base_url: Some("https://openrouter.ai/api/v1".to_string()),
            },
            deepinfra: BackendConfig {
                api_key: String::new(),
                model: String::new(),
                base_url: Some("https://api.deepinfra.com/v1/openai".to_string()),
            },
            prompts: PromptConfig {
                anthropic: "CLAUDE.md".to_string(),
                other: "POC.md".to_string(),
            },
            debug: false,
            compaction: CompactionConfig {
                hard_threshold_pct: 90,
                soft_threshold_pct: 80,
            },
            dmn: DmnConfig { max_turns: 20 },
            memory_project: None,
            system_prompt_file: None,
            models: HashMap::new(),
            default_model: String::new(),
        }
    }
}

fn default_model_name() -> String { String::new() }

// --- Json5File: figment provider ---

struct Json5File(PathBuf);

impl Provider for Json5File {
    fn metadata(&self) -> figment::Metadata {
        figment::Metadata::named(format!("JSON5 file ({})", self.0.display()))
    }

    fn data(&self) -> figment::Result<figment::value::Map<figment::Profile, figment::value::Dict>> {
        match std::fs::read_to_string(&self.0) {
            Ok(content) => {
                let value: figment::value::Value = json5::from_str(&content)
                    .map_err(|e| figment::Error::from(format!("{}: {}", self.0.display(), e)))?;
                Serialized::defaults(value).data()
            }
            Err(e) if e.kind() == std::io::ErrorKind::NotFound => Ok(figment::value::Map::new()),
            Err(e) => Err(figment::Error::from(format!("{}: {}", self.0.display(), e))),
        }
    }
}

// --- Figment construction ---

/// Merge an Option<T> into one or more figment keys.
macro_rules! merge_opt {
    ($fig:expr, $val:expr, $($key:expr),+) => {
        if let Some(ref v) = $val {
            $( $fig = $fig.merge(Serialized::default($key, v)); )+
        }
    };
}

fn build_figment(cli: &CliArgs) -> Figment {
    let config_path = dirs::home_dir()
        .unwrap_or_else(|| PathBuf::from("."))
        .join(".config/poc-agent/config.json5");

    let mut f = Figment::from(Serialized::defaults(AppConfig::default()))
        .merge(Json5File(config_path));

    // CLI overrides — model/key/base go to both backends
    merge_opt!(f, cli.backend, "backend");
    merge_opt!(f, cli.model, "anthropic.model", "openrouter.model");
    merge_opt!(f, cli.api_key, "anthropic.api_key", "openrouter.api_key");
    merge_opt!(f, cli.api_base, "anthropic.base_url", "openrouter.base_url");
    merge_opt!(f, cli.system_prompt_file, "system_prompt_file");
    merge_opt!(f, cli.memory_project, "memory_project");
    merge_opt!(f, cli.dmn_max_turns, "dmn.max_turns");
    if cli.debug {
        f = f.merge(Serialized::default("debug", true));
    }

    f
}

// --- Config loading ---

/// Resolved, ready-to-use config.
pub struct Config {
    pub api_base: String,
    pub api_key: String,
    pub model: String,
    pub prompt_file: String,
    pub system_prompt: String,
    /// Identity/personality files as (name, content) pairs.
    pub context_parts: Vec<(String, String)>,
    pub config_file_count: usize,
    pub memory_file_count: usize,
    pub session_dir: PathBuf,
    pub app: AppConfig,
}

impl Config {
    /// Join context parts into a single string for legacy interfaces.
    #[allow(dead_code)]
    pub fn context_message(&self) -> String {
        self.context_parts.iter()
            .map(|(name, content)| format!("## {}\n\n{}", name, content))
            .collect::<Vec<_>>()
            .join("\n\n---\n\n")
    }
}

/// A fully resolved model ready to construct an ApiClient.
#[allow(dead_code)]
pub struct ResolvedModel {
    pub name: String,
    pub api_base: String,
    pub api_key: String,
    pub model_id: String,
    pub prompt_file: String,
    pub context_window: Option<usize>,
}

impl AppConfig {
    /// Resolve the active backend and assemble prompts into a ready-to-use Config.
    pub fn resolve(&self, cli: &CliArgs) -> Result<Config> {
        let cwd = std::env::current_dir().context("Failed to get current directory")?;

        let (api_base, api_key, model, prompt_file);

        if !self.models.is_empty() {
            let resolved = self.resolve_model(&self.default_model)?;
            api_base = resolved.api_base;
            api_key = resolved.api_key;
            model = resolved.model_id;
            prompt_file = resolved.prompt_file;
        } else {
            // Legacy path — no models map, use backend field directly
            let (base, key, mdl) = match self.backend.as_str() {
                "anthropic" => self.anthropic.resolve("https://api.anthropic.com"),
                _ => self.openrouter.resolve("https://openrouter.ai/api/v1"),
            }?;
            api_base = base;
            api_key = key;
            model = mdl;
            prompt_file = if is_anthropic_model(&model) {
                self.prompts.anthropic.clone()
            } else {
                self.prompts.other.clone()
            };
        }

        let (system_prompt, context_parts, config_file_count, memory_file_count) =
            if let Some(ref path) = cli.system_prompt_file.as_ref().or(self.system_prompt_file.as_ref()) {
                let content = std::fs::read_to_string(path)
                    .with_context(|| format!("Failed to read {}", path.display()))?;
                (content, Vec::new(), 0, 0)
            } else {
                let system_prompt = crate::agent::identity::assemble_system_prompt();
                let context_groups = load_context_groups();
                let (context_parts, cc, mc) = crate::agent::identity::assemble_context_message(&cwd, &prompt_file, self.memory_project.as_deref(), &context_groups)?;
                (system_prompt, context_parts, cc, mc)
            };

        let session_dir = dirs::home_dir()
            .unwrap_or_else(|| PathBuf::from("."))
            .join(".cache/poc-agent/sessions");
        std::fs::create_dir_all(&session_dir).ok();

        Ok(Config {
            api_base, api_key, model, prompt_file,
            system_prompt, context_parts,
            config_file_count, memory_file_count,
            session_dir,
            app: self.clone(),
        })
    }

    /// Look up a named model and resolve its credentials from the backend config.
    pub fn resolve_model(&self, name: &str) -> Result<ResolvedModel> {
        let model = self.models.get(name)
            .ok_or_else(|| anyhow::anyhow!(
                "Unknown model '{}'. Available: {}",
                name,
                self.model_names().join(", "),
            ))?;

        let (api_base, api_key) = match model.backend.as_str() {
            "anthropic" => (
                self.anthropic.base_url.clone()
                    .unwrap_or_else(|| "https://api.anthropic.com".to_string()),
                self.anthropic.api_key.clone(),
            ),
            "deepinfra" => (
                self.deepinfra.base_url.clone()
                    .unwrap_or_else(|| "https://api.deepinfra.com/v1/openai".to_string()),
                self.deepinfra.api_key.clone(),
            ),
            _ => (
                self.openrouter.base_url.clone()
                    .unwrap_or_else(|| "https://openrouter.ai/api/v1".to_string()),
                self.openrouter.api_key.clone(),
            ),
        };

        let prompt_file = model.prompt_file.clone()
            .unwrap_or_else(|| {
                if is_anthropic_model(&model.model_id) {
                    self.prompts.anthropic.clone()
                } else {
                    self.prompts.other.clone()
                }
            });

        Ok(ResolvedModel {
            name: name.to_string(),
            api_base,
            api_key,
            model_id: model.model_id.clone(),
            prompt_file,
            context_window: model.context_window,
        })
    }

    /// List available model names, sorted.
    pub fn model_names(&self) -> Vec<String> {
        let mut names: Vec<_> = self.models.keys().cloned().collect();
        names.sort();
        names
    }
}

/// Load just the AppConfig — no validation, no prompt assembly.
pub fn load_app(cli: &CliArgs) -> Result<(AppConfig, Figment)> {
    let figment = build_figment(cli);
    let app: AppConfig = figment.extract().context("Failed to load configuration")?;
    Ok((app, figment))
}

/// Load the full config: figment → AppConfig → resolve backend → assemble prompts.
pub fn load(cli: &CliArgs) -> Result<(Config, Figment)> {
    let (app, figment) = load_app(cli)?;
    let config = app.resolve(cli)?;
    Ok((config, figment))
}

/// Load context_groups from the shared config file.
fn load_context_groups() -> Vec<crate::agent::identity::ContextGroup> {
    let config_path = dirs::home_dir()
        .unwrap_or_else(|| std::path::PathBuf::from("."))
        .join(".config/poc-agent/config.json5");
    
    if let Ok(content) = std::fs::read_to_string(&config_path) {
        let config: Result<serde_json::Value, _> = json5::from_str(&content);
        if let Ok(config) = config {
            if let Some(memory) = config.get("memory") {
                if let Some(groups) = memory.get("context_groups") {
                    if let Ok(context_groups) = serde_json::from_value(groups.clone()) {
                        return context_groups;
                    }
                }
            }
        }
    }
    Vec::new()
}

/// Re-assemble prompts for a specific model's prompt file.
pub fn reload_for_model(app: &AppConfig, prompt_file: &str) -> Result<(String, Vec<(String, String)>)> {
    let cwd = std::env::current_dir().context("Failed to get current directory")?;

    if let Some(ref path) = app.system_prompt_file {
        let content = std::fs::read_to_string(path)
            .with_context(|| format!("Failed to read {}", path.display()))?;
        return Ok((content, Vec::new()));
    }

    let system_prompt = crate::agent::identity::assemble_system_prompt();
    let context_groups = load_context_groups();
    let (context_parts, _, _) = crate::agent::identity::assemble_context_message(&cwd, prompt_file, app.memory_project.as_deref(), &context_groups)?;
    Ok((system_prompt, context_parts))
}


fn is_anthropic_model(model: &str) -> bool {
    let m = model.to_lowercase();
    m.contains("claude") || m.contains("opus") || m.contains("sonnet")
}

// --- --show-config ---

pub fn show_config(app: &AppConfig, figment: &Figment) {
    fn mask(key: &str) -> String {
        if key.is_empty() { "(not set)".into() }
        else if key.len() <= 8 { "****".into() }
        else { format!("{}...{}", &key[..4], &key[key.len() - 4..]) }
    }
    fn src(figment: &Figment, key: &str) -> String {
        figment.find_metadata(key).map_or("default".into(), |m| m.name.to_string())
    }

    println!("# Effective configuration\n");
    println!("backend: {:?}  ({})", app.backend, src(figment, "backend"));
    for (name, b) in [("anthropic", &app.anthropic), ("openrouter", &app.openrouter)] {
        println!("\n{}:", name);
        println!("  api_key: {}  ({})", mask(&b.api_key), src(figment, &format!("{name}.api_key")));
        println!("  model: {:?}  ({})", b.model, src(figment, &format!("{name}.model")));
        if let Some(ref url) = b.base_url {
            println!("  base_url: {:?}  ({})", url, src(figment, &format!("{name}.base_url")));
        }
    }
    println!("\nprompts:");
    println!("  anthropic: {:?}  ({})", app.prompts.anthropic, src(figment, "prompts.anthropic"));
    println!("  other: {:?}  ({})", app.prompts.other, src(figment, "prompts.other"));
    println!("\ndebug: {}  ({})", app.debug, src(figment, "debug"));
    println!("\ncompaction:");
    println!("  hard_threshold_pct: {}  ({})", app.compaction.hard_threshold_pct, src(figment, "compaction.hard_threshold_pct"));
    println!("  soft_threshold_pct: {}  ({})", app.compaction.soft_threshold_pct, src(figment, "compaction.soft_threshold_pct"));
    println!("\ndmn:");
    println!("  max_turns: {}  ({})", app.dmn.max_turns, src(figment, "dmn.max_turns"));
    if let Some(ref p) = app.system_prompt_file {
        println!("\nsystem_prompt_file: {:?}  ({})", p, src(figment, "system_prompt_file"));
    }
    if let Some(ref p) = app.memory_project {
        println!("\nmemory_project: {:?}  ({})", p, src(figment, "memory_project"));
    }
    println!("\ndefault_model: {:?}", app.default_model);
    if !app.models.is_empty() {
        println!("\nmodels:");
        for (name, m) in &app.models {
            println!("  {}:", name);
            println!("    backend: {:?}", m.backend);
            println!("    model_id: {:?}", m.model_id);
            if let Some(ref pf) = m.prompt_file {
                println!("    prompt_file: {:?}", pf);
            }
            if let Some(cw) = m.context_window {
                println!("    context_window: {}", cw);
            }
        }
    }
}

// Identity file discovery and context assembly live in identity.rs