use std::fs::File;
use std::io::{BufRead, BufReader};
use std::path::{Path, PathBuf};
use std::sync::LazyLock;

use regex::Regex;
use serde_json::Value;

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

use super::utils::{
    extract_text, parse_timestamp_to_ms, path_basename, read_head_tail_lines, truncate_summary,
};

const PROVIDER_ID: &str = "codex";

static UUID_RE: LazyLock<Regex> = LazyLock::new(|| {
    Regex::new(r"[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}")
        .unwrap()
});

pub fn scan_sessions() -> Vec<SessionMeta> {
    let root = get_codex_config_dir().join("sessions");
    let mut files = Vec::new();
    collect_jsonl_files(&root, &mut files);

    let mut sessions = Vec::new();
    for path in files {
        if let Some(meta) = parse_session(&path) {
            sessions.push(meta);
        }
    }

    sessions
}

pub fn load_messages(path: &Path) -> Result<Vec<SessionMessage>, String> {
    let file = File::open(path).map_err(|e| format!("Failed to open session file: {e}"))?;
    let reader = BufReader::new(file);
    let mut messages = Vec::new();

    for line in reader.lines() {
        let line = match line {
            Ok(value) => value,
            Err(_) => continue,
        };
        let value: Value = match serde_json::from_str(&line) {
            Ok(parsed) => parsed,
            Err(_) => continue,
        };

        if value.get("type").and_then(Value::as_str) != Some("response_item") {
            continue;
        }

        let payload = match value.get("payload") {
            Some(payload) => payload,
            None => continue,
        };

        let payload_type = payload.get("type").and_then(Value::as_str).unwrap_or("");

        // Codex uses separate payload types for tool interactions
        let (role, content) = match payload_type {
            "message" => {
                let role = payload
                    .get("role")
                    .and_then(Value::as_str)
                    .unwrap_or("unknown")
                    .to_string();
                let content = payload.get("content").map(extract_text).unwrap_or_default();
                (role, content)
            }
            "function_call" => {
                let name = payload
                    .get("name")
                    .and_then(Value::as_str)
                    .unwrap_or("unknown");
                ("assistant".to_string(), format!("[Tool: {name}]"))
            }
            "function_call_output" => {
                let output = payload
                    .get("output")
                    .and_then(Value::as_str)
                    .unwrap_or("")
                    .to_string();
                ("tool".to_string(), output)
            }
            _ => continue,
        };

        if content.trim().is_empty() {
            continue;
        }

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

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

    Ok(messages)
}

pub fn delete_session(_root: &Path, path: &Path, session_id: &str) -> Result<bool, String> {
    let meta = parse_session(path)
        .ok_or_else(|| format!("Failed to parse Codex session metadata: {}", path.display()))?;

    if meta.session_id != session_id {
        return Err(format!(
            "Codex session ID mismatch: expected {session_id}, found {}",
            meta.session_id
        ));
    }

    std::fs::remove_file(path).map_err(|e| {
        format!(
            "Failed to delete Codex session file {}: {e}",
            path.display()
        )
    })?;

    Ok(true)
}

fn parse_session(path: &Path) -> Option<SessionMeta> {
    let (head, tail) = read_head_tail_lines(path, 10, 30).ok()?;

    let mut session_id: Option<String> = None;
    let mut project_dir: Option<String> = None;
    let mut created_at: Option<i64> = None;

    // Extract metadata from head lines
    for line in &head {
        let value: Value = match serde_json::from_str(line) {
            Ok(parsed) => parsed,
            Err(_) => continue,
        };
        if created_at.is_none() {
            created_at = value.get("timestamp").and_then(parse_timestamp_to_ms);
        }
        if value.get("type").and_then(Value::as_str) == Some("session_meta") {
            if let Some(payload) = value.get("payload") {
                if session_id.is_none() {
                    session_id = payload
                        .get("id")
                        .and_then(Value::as_str)
                        .map(|s| s.to_string());
                }
                if project_dir.is_none() {
                    project_dir = payload
                        .get("cwd")
                        .and_then(Value::as_str)
                        .map(|s| s.to_string());
                }
                if let Some(ts) = payload.get("timestamp").and_then(parse_timestamp_to_ms) {
                    created_at.get_or_insert(ts);
                }
            }
        }
    }

    // Extract last_active_at and summary from tail lines (reverse order)
    let mut last_active_at: Option<i64> = None;
    let mut summary: Option<String> = None;

    for line in tail.iter().rev() {
        let value: Value = match serde_json::from_str(line) {
            Ok(parsed) => parsed,
            Err(_) => continue,
        };
        if last_active_at.is_none() {
            last_active_at = value.get("timestamp").and_then(parse_timestamp_to_ms);
        }
        if summary.is_none() && value.get("type").and_then(Value::as_str) == Some("response_item") {
            if let Some(payload) = value.get("payload") {
                if payload.get("type").and_then(Value::as_str) == Some("message") {
                    let text = payload.get("content").map(extract_text).unwrap_or_default();
                    if !text.trim().is_empty() {
                        summary = Some(text);
                    }
                }
            }
        }
        if last_active_at.is_some() && summary.is_some() {
            break;
        }
    }

    let session_id = session_id.or_else(|| infer_session_id_from_filename(path));
    let session_id = session_id?;

    let title = project_dir
        .as_deref()
        .and_then(path_basename)
        .map(|value| value.to_string());

    let summary = summary.map(|text| truncate_summary(&text, 160));

    Some(SessionMeta {
        provider_id: PROVIDER_ID.to_string(),
        session_id: session_id.clone(),
        title,
        summary,
        project_dir,
        created_at,
        last_active_at,
        source_path: Some(path.to_string_lossy().to_string()),
        resume_command: Some(format!("codex resume {session_id}")),
    })
}

fn infer_session_id_from_filename(path: &Path) -> Option<String> {
    let file_name = path.file_name()?.to_string_lossy();
    UUID_RE.find(&file_name).map(|mat| mat.as_str().to_string())
}

fn collect_jsonl_files(root: &Path, files: &mut Vec<PathBuf>) {
    if !root.exists() {
        return;
    }

    let entries = match std::fs::read_dir(root) {
        Ok(entries) => entries,
        Err(_) => return,
    };

    for entry in entries.flatten() {
        let path = entry.path();
        if path.is_dir() {
            collect_jsonl_files(&path, files);
        } else if path.extension().and_then(|ext| ext.to_str()) == Some("jsonl") {
            files.push(path);
        }
    }
}

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

    #[test]
    fn delete_session_removes_jsonl_file() {
        let temp = tempdir().expect("tempdir");
        let path = temp
            .path()
            .join("rollout-2026-03-06T21-50-12-019cc369-bd7c-7891-b371-7b20b4fe0b18.jsonl");
        std::fs::write(
            &path,
            concat!(
                "{\"timestamp\":\"2026-03-06T21:50:12Z\",\"type\":\"session_meta\",\"payload\":{\"id\":\"019cc369-bd7c-7891-b371-7b20b4fe0b18\",\"cwd\":\"/tmp/project\"}}\n",
                "{\"timestamp\":\"2026-03-06T21:50:13Z\",\"type\":\"response_item\",\"payload\":{\"type\":\"message\",\"role\":\"user\",\"content\":\"hello\"}}\n"
            ),
        )
        .expect("write session");

        delete_session(temp.path(), &path, "019cc369-bd7c-7891-b371-7b20b4fe0b18")
            .expect("delete session");

        assert!(!path.exists());
    }

    #[test]
    fn load_messages_includes_function_call_and_output() {
        let temp = tempdir().expect("tempdir");
        let path = temp.path().join("session.jsonl");
        std::fs::write(
            &path,
            concat!(
                "{\"timestamp\":\"2026-03-06T21:50:12Z\",\"type\":\"session_meta\",\"payload\":{\"id\":\"test-id\",\"cwd\":\"/tmp\"}}\n",
                "{\"timestamp\":\"2026-03-06T21:50:13Z\",\"type\":\"response_item\",\"payload\":{\"type\":\"message\",\"role\":\"user\",\"content\":\"list files\"}}\n",
                "{\"timestamp\":\"2026-03-06T21:50:14Z\",\"type\":\"response_item\",\"payload\":{\"type\":\"function_call\",\"name\":\"shell\",\"arguments\":\"{\\\"cmd\\\":[\\\"ls\\\"]}\",\"call_id\":\"call_1\"}}\n",
                "{\"timestamp\":\"2026-03-06T21:50:15Z\",\"type\":\"response_item\",\"payload\":{\"type\":\"function_call_output\",\"call_id\":\"call_1\",\"output\":\"file1.txt\\nfile2.txt\"}}\n",
                "{\"timestamp\":\"2026-03-06T21:50:16Z\",\"type\":\"response_item\",\"payload\":{\"type\":\"message\",\"role\":\"assistant\",\"content\":[{\"type\":\"output_text\",\"text\":\"Done.\"}]}}\n",
            ),
        )
        .expect("write");

        let msgs = load_messages(&path).expect("load");
        assert_eq!(msgs.len(), 4);

        assert_eq!(msgs[0].role, "user");
        assert_eq!(msgs[0].content, "list files");

        assert_eq!(msgs[1].role, "assistant");
        assert!(msgs[1].content.contains("[Tool: shell]"));

        assert_eq!(msgs[2].role, "tool");
        assert!(msgs[2].content.contains("file1.txt"));

        assert_eq!(msgs[3].role, "assistant");
        assert_eq!(msgs[3].content, "Done.");
    }
}