use std::env;
use std::path::{Path, PathBuf};

use commands::handle_slash_command;
use compat_harness::{extract_manifest, UpstreamPaths};
use runtime::{load_system_prompt, BootstrapPlan, CompactionConfig, Session};

fn main() {
    let args: Vec<String> = env::args().skip(1).collect();

    match parse_args(&args) {
        Ok(CliAction::DumpManifests) => dump_manifests(),
        Ok(CliAction::BootstrapPlan) => print_bootstrap_plan(),
        Ok(CliAction::PrintSystemPrompt { cwd, date }) => print_system_prompt(cwd, date),
        Ok(CliAction::ResumeSession {
            session_path,
            command,
        }) => resume_session(&session_path, command),
        Ok(CliAction::Help) => print_help(),
        Err(error) => {
            eprintln!("{error}");
            print_help();
            std::process::exit(2);
        }
    }
}

#[derive(Debug, Clone, PartialEq, Eq)]
enum CliAction {
    DumpManifests,
    BootstrapPlan,
    PrintSystemPrompt {
        cwd: PathBuf,
        date: String,
    },
    ResumeSession {
        session_path: PathBuf,
        command: Option<String>,
    },
    Help,
}

fn parse_args(args: &[String]) -> Result<CliAction, String> {
    if args.is_empty() {
        return Ok(CliAction::Help);
    }

    if matches!(args.first().map(String::as_str), Some("--help" | "-h")) {
        return Ok(CliAction::Help);
    }

    if args.first().map(String::as_str) == Some("--resume") {
        return parse_resume_args(&args[1..]);
    }

    match args[0].as_str() {
        "dump-manifests" => Ok(CliAction::DumpManifests),
        "bootstrap-plan" => Ok(CliAction::BootstrapPlan),
        "system-prompt" => parse_system_prompt_args(&args[1..]),
        other => Err(format!("unknown subcommand: {other}")),
    }
}

fn parse_system_prompt_args(args: &[String]) -> Result<CliAction, String> {
    let mut cwd = env::current_dir().map_err(|error| error.to_string())?;
    let mut date = "2026-03-31".to_string();
    let mut index = 0;

    while index < args.len() {
        match args[index].as_str() {
            "--cwd" => {
                let value = args
                    .get(index + 1)
                    .ok_or_else(|| "missing value for --cwd".to_string())?;
                cwd = PathBuf::from(value);
                index += 2;
            }
            "--date" => {
                let value = args
                    .get(index + 1)
                    .ok_or_else(|| "missing value for --date".to_string())?;
                date.clone_from(value);
                index += 2;
            }
            other => return Err(format!("unknown system-prompt option: {other}")),
        }
    }

    Ok(CliAction::PrintSystemPrompt { cwd, date })
}

fn parse_resume_args(args: &[String]) -> Result<CliAction, String> {
    let session_path = args
        .first()
        .ok_or_else(|| "missing session path for --resume".to_string())
        .map(PathBuf::from)?;
    let command = args.get(1).cloned();
    if args.len() > 2 {
        return Err("--resume accepts at most one trailing slash command".to_string());
    }
    Ok(CliAction::ResumeSession {
        session_path,
        command,
    })
}

fn dump_manifests() {
    let workspace_dir = PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("../..");
    let paths = UpstreamPaths::from_workspace_dir(&workspace_dir);
    match extract_manifest(&paths) {
        Ok(manifest) => {
            println!("commands: {}", manifest.commands.entries().len());
            println!("tools: {}", manifest.tools.entries().len());
            println!("bootstrap phases: {}", manifest.bootstrap.phases().len());
        }
        Err(error) => {
            eprintln!("failed to extract manifests: {error}");
            std::process::exit(1);
        }
    }
}

fn print_bootstrap_plan() {
    for phase in BootstrapPlan::claude_code_default().phases() {
        println!("- {phase:?}");
    }
}

fn print_system_prompt(cwd: PathBuf, date: String) {
    match load_system_prompt(cwd, date, env::consts::OS, "unknown") {
        Ok(sections) => println!("{}", sections.join("\n\n")),
        Err(error) => {
            eprintln!("failed to build system prompt: {error}");
            std::process::exit(1);
        }
    }
}

fn resume_session(session_path: &Path, command: Option<String>) {
    let session = match Session::load_from_path(session_path) {
        Ok(session) => session,
        Err(error) => {
            eprintln!("failed to restore session: {error}");
            std::process::exit(1);
        }
    };

    match command {
        Some(command) if command.starts_with('/') => {
            let Some(result) = handle_slash_command(
                &command,
                &session,
                CompactionConfig {
                    max_estimated_tokens: 0,
                    ..CompactionConfig::default()
                },
            ) else {
                eprintln!("unknown slash command: {command}");
                std::process::exit(2);
            };
            if let Err(error) = result.session.save_to_path(session_path) {
                eprintln!("failed to persist resumed session: {error}");
                std::process::exit(1);
            }
            println!("{}", result.message);
        }
        Some(other) => {
            eprintln!("unsupported resumed command: {other}");
            std::process::exit(2);
        }
        None => {
            println!(
                "Restored session from {} ({} messages).",
                session_path.display(),
                session.messages.len()
            );
        }
    }
}

fn print_help() {
    println!("rusty-claude-cli");
    println!();
    println!("Current scaffold commands:");
    println!(
        "  dump-manifests                   Read upstream TS sources and print extracted counts"
    );
    println!("  bootstrap-plan                   Print the current bootstrap phase skeleton");
    println!("  system-prompt [--cwd PATH] [--date YYYY-MM-DD]");
    println!("                                   Build a Claude-style system prompt from CLAUDE.md and config files");
    println!("  --resume SESSION.json [/compact] Restore a saved session and optionally run a slash command");
}

#[cfg(test)]
mod tests {
    use super::{parse_args, CliAction};
    use std::path::PathBuf;

    #[test]
    fn parses_system_prompt_options() {
        let args = vec![
            "system-prompt".to_string(),
            "--cwd".to_string(),
            "/tmp/project".to_string(),
            "--date".to_string(),
            "2026-04-01".to_string(),
        ];
        assert_eq!(
            parse_args(&args).expect("args should parse"),
            CliAction::PrintSystemPrompt {
                cwd: PathBuf::from("/tmp/project"),
                date: "2026-04-01".to_string(),
            }
        );
    }

    #[test]
    fn parses_resume_flag_with_slash_command() {
        let args = vec![
            "--resume".to_string(),
            "session.json".to_string(),
            "/compact".to_string(),
        ];
        assert_eq!(
            parse_args(&args).expect("args should parse"),
            CliAction::ResumeSession {
                session_path: PathBuf::from("session.json"),
                command: Some("/compact".to_string()),
            }
        );
    }
}