use std::path::Path;

use anyhow::{Result, bail};
use async_trait::async_trait;
use dap::{DapLocator, DebugRequest, adapters::DebugAdapterName};
use gpui::SharedString;

use task::{DebugScenario, SpawnInTerminal, TaskTemplate, VariableName};

pub(crate) struct PythonLocator;

#[async_trait]
impl DapLocator for PythonLocator {
    fn name(&self) -> SharedString {
        SharedString::new_static("Python")
    }

    /// Determines whether this locator can generate debug target for given task.
    async fn create_scenario(
        &self,
        build_config: &TaskTemplate,
        resolved_label: &str,
        adapter: &DebugAdapterName,
    ) -> Option<DebugScenario> {
        if adapter.0.as_ref() != "Debugpy" {
            return None;
        }
        let valid_program = build_config.command.starts_with("$ZED_")
            || Path::new(&build_config.command)
                .file_name()
                .map_or(false, |name| {
                    name.to_str().is_some_and(|path| path.starts_with("python"))
                });
        if !valid_program || build_config.args.iter().any(|arg| arg == "-c") {
            // We cannot debug selections.
            return None;
        }
        let command = if build_config.command
            == VariableName::Custom("PYTHON_ACTIVE_ZED_TOOLCHAIN".into()).template_value()
        {
            VariableName::Custom("PYTHON_ACTIVE_ZED_TOOLCHAIN_RAW".into()).template_value()
        } else {
            build_config.command.clone()
        };
        let module_specifier_position = build_config
            .args
            .iter()
            .position(|arg| arg == "-m")
            .map(|position| position + 1);
        // Skip the -m and module name, get all that's after.
        let mut rest_of_the_args = module_specifier_position
            .and_then(|position| build_config.args.get(position..))
            .into_iter()
            .flatten()
            .fuse();
        let mod_name = rest_of_the_args.next();
        let args = rest_of_the_args.collect::<Vec<_>>();

        let program_position = mod_name
            .is_none()
            .then(|| {
                build_config
                    .args
                    .iter()
                    .position(|arg| *arg == "\"$ZED_FILE\"")
            })
            .flatten();
        let args = if let Some(position) = program_position {
            args.into_iter().skip(position).collect::<Vec<_>>()
        } else {
            args
        };
        if program_position.is_none() && mod_name.is_none() {
            return None;
        }
        let mut config = serde_json::json!({
            "request": "launch",
            "python": command,
            "args": args,
            "cwd": build_config.cwd.clone()
        });
        if let Some(config_obj) = config.as_object_mut() {
            if let Some(module) = mod_name {
                config_obj.insert("module".to_string(), module.clone().into());
            }
            if let Some(program) = program_position {
                config_obj.insert(
                    "program".to_string(),
                    build_config.args[program].clone().into(),
                );
            }
        }

        Some(DebugScenario {
            adapter: adapter.0.clone(),
            label: resolved_label.to_string().into(),
            build: None,
            config,
            tcp_connection: None,
        })
    }

    async fn run(&self, _: SpawnInTerminal) -> Result<DebugRequest> {
        bail!("Python locator should not require DapLocator::run to be ran");
    }
}