use std::sync::Arc;

use crate::Db;
use crate::module_resolver::SearchPaths;
use crate::python_platform::PythonPlatform;
use crate::site_packages::SysPrefixPathOrigin;

use anyhow::Context;
use ruff_db::system::{SystemPath, SystemPathBuf};
use ruff_python_ast::PythonVersion;
use ruff_text_size::TextRange;
use salsa::Durability;
use salsa::Setter;

#[salsa::input(singleton)]
pub struct Program {
    #[returns(ref)]
    pub python_version_with_source: PythonVersionWithSource,

    #[returns(ref)]
    pub python_platform: PythonPlatform,

    #[returns(ref)]
    pub(crate) search_paths: SearchPaths,
}

impl Program {
    pub fn from_settings(db: &dyn Db, settings: ProgramSettings) -> anyhow::Result<Self> {
        let ProgramSettings {
            python_version: python_version_with_source,
            python_platform,
            search_paths,
        } = settings;

        tracing::info!(
            "Python version: Python {python_version}, platform: {python_platform}",
            python_version = python_version_with_source.version
        );

        let search_paths = SearchPaths::from_settings(db, &search_paths)
            .with_context(|| "Invalid search path settings")?;

        Ok(
            Program::builder(python_version_with_source, python_platform, search_paths)
                .durability(Durability::HIGH)
                .new(db),
        )
    }

    pub fn python_version(self, db: &dyn Db) -> PythonVersion {
        self.python_version_with_source(db).version
    }

    pub fn update_from_settings(
        self,
        db: &mut dyn Db,
        settings: ProgramSettings,
    ) -> anyhow::Result<()> {
        let ProgramSettings {
            python_version,
            python_platform,
            search_paths,
        } = settings;

        if &python_platform != self.python_platform(db) {
            tracing::debug!("Updating python platform: `{python_platform:?}`");
            self.set_python_platform(db).to(python_platform);
        }

        if &python_version != self.python_version_with_source(db) {
            tracing::debug!("Updating python version: `{python_version:?}`");
            self.set_python_version_with_source(db).to(python_version);
        }

        self.update_search_paths(db, &search_paths)?;

        Ok(())
    }

    pub fn update_search_paths(
        self,
        db: &mut dyn Db,
        search_path_settings: &SearchPathSettings,
    ) -> anyhow::Result<()> {
        let search_paths = SearchPaths::from_settings(db, search_path_settings)?;

        if self.search_paths(db) != &search_paths {
            tracing::debug!("Update search paths");
            self.set_search_paths(db).to(search_paths);
        }

        Ok(())
    }

    pub fn custom_stdlib_search_path(self, db: &dyn Db) -> Option<&SystemPath> {
        self.search_paths(db).custom_stdlib()
    }
}

#[derive(Clone, Debug, Eq, PartialEq)]
pub struct ProgramSettings {
    pub python_version: PythonVersionWithSource,
    pub python_platform: PythonPlatform,
    pub search_paths: SearchPathSettings,
}

#[derive(Clone, Debug, Eq, PartialEq, Default)]
pub enum PythonVersionSource {
    /// Value loaded from a project's configuration file.
    File(Arc<SystemPathBuf>, Option<TextRange>),

    /// The value comes from a CLI argument, while it's left open if specified using a short argument,
    /// long argument (`--extra-paths`) or `--config key=value`.
    Cli,

    /// We fell back to a default value because the value was not specified via the CLI or a config file.
    #[default]
    Default,
}

#[derive(Eq, PartialEq, Debug, Clone)]
pub struct PythonVersionWithSource {
    pub version: PythonVersion,
    pub source: PythonVersionSource,
}

impl Default for PythonVersionWithSource {
    fn default() -> Self {
        Self {
            version: PythonVersion::latest_ty(),
            source: PythonVersionSource::Default,
        }
    }
}

/// Configures the search paths for module resolution.
#[derive(Eq, PartialEq, Debug, Clone)]
#[cfg_attr(feature = "serde", derive(serde::Serialize))]
pub struct SearchPathSettings {
    /// List of user-provided paths that should take first priority in the module resolution.
    /// Examples in other type checkers are mypy's MYPYPATH environment variable,
    /// or pyright's stubPath configuration setting.
    pub extra_paths: Vec<SystemPathBuf>,

    /// The root of the project, used for finding first-party modules.
    pub src_roots: Vec<SystemPathBuf>,

    /// Optional path to a "custom typeshed" directory on disk for us to use for standard-library types.
    /// If this is not provided, we will fallback to our vendored typeshed stubs for the stdlib,
    /// bundled as a zip file in the binary
    pub custom_typeshed: Option<SystemPathBuf>,

    /// Path to the Python installation from which ty resolves third party dependencies
    /// and their type information.
    pub python_path: PythonPath,
}

impl SearchPathSettings {
    pub fn new(src_roots: Vec<SystemPathBuf>) -> Self {
        Self {
            src_roots,
            extra_paths: vec![],
            custom_typeshed: None,
            python_path: PythonPath::KnownSitePackages(vec![]),
        }
    }
}

#[derive(Debug, Clone, Eq, PartialEq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub enum PythonPath {
    /// A path that represents the value of [`sys.prefix`] at runtime in Python
    /// for a given Python executable.
    ///
    /// For the case of a virtual environment, where a
    /// Python binary is at `/.venv/bin/python`, `sys.prefix` is the path to
    /// the virtual environment the Python binary lies inside, i.e. `/.venv`,
    /// and `site-packages` will be at `.venv/lib/python3.X/site-packages`.
    /// System Python installations generally work the same way: if a system
    /// Python installation lies at `/opt/homebrew/bin/python`, `sys.prefix`
    /// will be `/opt/homebrew`, and `site-packages` will be at
    /// `/opt/homebrew/lib/python3.X/site-packages`.
    ///
    /// [`sys.prefix`]: https://docs.python.org/3/library/sys.html#sys.prefix
    SysPrefix(SystemPathBuf, SysPrefixPathOrigin),

    /// Resolve a path to an executable (or environment directory) into a usable environment.
    Resolve(SystemPathBuf, SysPrefixPathOrigin),

    /// Tries to discover a virtual environment in the given path.
    Discover(SystemPathBuf),

    /// Resolved site packages paths.
    ///
    /// This variant is mainly intended for testing where we want to skip resolving `site-packages`
    /// because it would unnecessarily complicate the test setup.
    KnownSitePackages(Vec<SystemPathBuf>),
}

impl PythonPath {
    pub fn from_virtual_env_var(path: impl Into<SystemPathBuf>) -> Self {
        Self::SysPrefix(path.into(), SysPrefixPathOrigin::VirtualEnvVar)
    }

    pub fn from_cli_flag(path: SystemPathBuf) -> Self {
        Self::Resolve(path, SysPrefixPathOrigin::PythonCliFlag)
    }
}