use std::path::Path;

use serde_json::Value;

use crate::session_manager::{SessionMessage, SessionMeta};

use super::utils::{parse_timestamp_to_ms, truncate_summary};

const PROVIDER_ID: &str = "gemini";

pub fn scan_sessions() -> Vec<SessionMeta> {
    let gemini_dir = crate::gemini_config::get_gemini_dir();
    let tmp_dir = gemini_dir.join("tmp");
    if !tmp_dir.exists() {
        return Vec::new();
    }

    let mut sessions = Vec::new();

    // Iterate over project hash directories: tmp/<project_hash>/chats/session-*.json
    let project_dirs = match std::fs::read_dir(&tmp_dir) {
        Ok(entries) => entries,
        Err(_) => return Vec::new(),
    };

    for entry in project_dirs.flatten() {
        let chats_dir = entry.path().join("chats");
        if !chats_dir.is_dir() {
            continue;
        }

        let chat_files = match std::fs::read_dir(&chats_dir) {
            Ok(entries) => entries,
            Err(_) => continue,
        };

        for file_entry in chat_files.flatten() {
            let path = file_entry.path();
            if path.extension().and_then(|e| e.to_str()) != Some("json") {
                continue;
            }
            if let Some(meta) = parse_session(&path) {
                sessions.push(meta);
            }
        }
    }

    sessions
}

pub fn load_messages(path: &Path) -> Result<Vec<SessionMessage>, String> {
    let data = std::fs::read_to_string(path).map_err(|e| format!("Failed to read session: {e}"))?;
    let value: Value =
        serde_json::from_str(&data).map_err(|e| format!("Failed to parse session JSON: {e}"))?;

    let messages = value
        .get("messages")
        .and_then(Value::as_array)
        .ok_or_else(|| "No messages array found".to_string())?;

    let mut result = Vec::new();
    for msg in messages {
        let content = match msg.get("content").and_then(Value::as_str) {
            Some(c) if !c.trim().is_empty() => c.to_string(),
            _ => continue,
        };

        let role = match msg.get("type").and_then(Value::as_str) {
            Some("gemini") => "assistant".to_string(),
            Some("user") => "user".to_string(),
            Some(other) => other.to_string(),
            None => continue,
        };

        let ts = msg.get("timestamp").and_then(parse_timestamp_to_ms);

        result.push(SessionMessage { role, content, ts });
    }

    Ok(result)
}

fn parse_session(path: &Path) -> Option<SessionMeta> {
    let data = std::fs::read_to_string(path).ok()?;
    let value: Value = serde_json::from_str(&data).ok()?;

    let session_id = value.get("sessionId").and_then(Value::as_str)?.to_string();

    let created_at = value.get("startTime").and_then(parse_timestamp_to_ms);
    let last_active_at = value.get("lastUpdated").and_then(parse_timestamp_to_ms);

    // Derive title from first user message
    let title = value
        .get("messages")
        .and_then(Value::as_array)
        .and_then(|msgs| {
            msgs.iter()
                .find(|m| m.get("type").and_then(Value::as_str) == Some("user"))
                .and_then(|m| m.get("content").and_then(Value::as_str))
                .filter(|s| !s.trim().is_empty())
                .map(|s| truncate_summary(s, 160))
        });

    let source_path = path.to_string_lossy().to_string();

    Some(SessionMeta {
        provider_id: PROVIDER_ID.to_string(),
        session_id: session_id.clone(),
        title: title.clone(),
        summary: title,
        project_dir: None, // project hash is not reversible
        created_at,
        last_active_at: last_active_at.or(created_at),
        source_path: Some(source_path),
        resume_command: Some(format!("gemini --resume {session_id}")),
    })
}