use std::fmt;
use std::path::{Path, PathBuf};
use std::sync::Arc;

use anyhow::Result;
#[cfg(not(target_arch = "wasm32"))]
use command::r#async::Command;
use lsp_types::{
    ClientCapabilities, ClientInfo, CodeActionClientCapabilities, CompletionClientCapabilities,
    CompletionItemCapability, CompletionItemCapabilityResolveSupport,
    DidChangeWatchedFilesClientCapabilities, GotoCapability, HoverClientCapabilities,
    InitializeParams, MarkupKind, PublishDiagnosticsClientCapabilities, RenameClientCapabilities,
    SignatureHelpClientCapabilities, TextDocumentClientCapabilities,
    TextDocumentSyncClientCapabilities, Uri, WindowClientCapabilities, WorkDoneProgressParams,
    WorkspaceClientCapabilities, WorkspaceFolder,
};

use crate::supported_servers::LSPServerType;

/// Result of resolving an LSP server command, including the command and init params.
#[cfg(not(target_arch = "wasm32"))]
pub struct ResolvedLspCommand {
    pub command: Command,
    pub params: InitializeParams,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum LanguageId {
    Rust,
    Go,
    Python,
    TypeScript,
    TypeScriptReact,
    JavaScript,
    JavaScriptReact,
    C,
    Cpp,
}

impl LanguageId {
    pub fn from_path(path: &Path) -> Option<Self> {
        let extn = path.extension()?;
        match extn.to_str()? {
            "rs" => Some(Self::Rust),
            "go" => Some(Self::Go),
            "py" => Some(Self::Python),
            "ts" => Some(Self::TypeScript),
            "tsx" => Some(Self::TypeScriptReact),
            "js" | "mjs" | "cjs" => Some(Self::JavaScript),
            "jsx" => Some(Self::JavaScriptReact),
            "c" | "C" => Some(Self::C),
            "cc" | "cpp" | "cxx" => Some(Self::Cpp),
            // NOTE: `.h` files are ambiguous (could be C or C++). We map them to Cpp
            // because clangd defaults to C++ for `.h` files anyway. When a
            // compile_commands.json is present, clangd will use the correct language
            // regardless of the languageId we send.
            "h" | "H" | "hh" | "hpp" | "hxx" => Some(Self::Cpp),
            _ => None,
        }
    }

    /// Returns the language identifier as used by LSP.
    /// See: https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocumentItem
    pub(crate) fn lsp_language_identifier(&self) -> &'static str {
        match self {
            LanguageId::Rust => "rust",
            LanguageId::Go => "go",
            LanguageId::Python => "python",
            LanguageId::TypeScript => "typescript",
            LanguageId::TypeScriptReact => "typescriptreact",
            LanguageId::JavaScript => "javascript",
            LanguageId::JavaScriptReact => "javascriptreact",
            LanguageId::C => "c",
            LanguageId::Cpp => "cpp",
        }
    }

    /// For now we assume a 1:1 language -> LSP server type. This might change in the future as we support more configurabilities.
    pub fn server_type(&self) -> LSPServerType {
        match self {
            LanguageId::Rust => LSPServerType::RustAnalyzer,
            LanguageId::Go => LSPServerType::GoPls,
            LanguageId::Python => LSPServerType::Pyright,
            LanguageId::TypeScript
            | LanguageId::TypeScriptReact
            | LanguageId::JavaScript
            | LanguageId::JavaScriptReact => LSPServerType::TypeScriptLanguageServer,
            LanguageId::C | LanguageId::Cpp => LSPServerType::Clangd,
        }
    }
}

/// Configuration for spawning an LSP server process.
#[derive(Clone)]
#[cfg_attr(target_arch = "wasm32", allow(dead_code))]
pub struct LspServerConfig {
    server_type: LSPServerType,
    initial_workspace: PathBuf,
    /// The local PATH variable set when starting the server. This is needed when the app is started
    /// without a shell based parent process.
    /// TODO(kevin): This might not be sufficient for all cases (e.g. user might remove LSP from PATH).
    path_env_var: Option<String>,
    client_name: String,
    /// Shared HTTP client used for LSP installation checks and downloads.
    client: Arc<http_client::Client>,
    /// Optional path relative to the LSP log namespace for server stderr output.
    log_relative_path: Option<PathBuf>,
}

impl fmt::Debug for LspServerConfig {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("LspServerConfig")
            .field("server_type", &self.server_type)
            .field("initial_workspace", &self.initial_workspace)
            .field("path_env_var", &self.path_env_var)
            .field("client_name", &self.client_name)
            .field("log_relative_path", &self.log_relative_path)
            .finish()
    }
}

impl LspServerConfig {
    pub fn new(
        server_type: LSPServerType,
        initial_workspace: PathBuf,
        path_env_var: Option<String>,
        client_name: String,
        client: Arc<http_client::Client>,
    ) -> Self {
        Self {
            server_type,
            initial_workspace,
            path_env_var,
            client_name,
            client,
            log_relative_path: None,
        }
    }

    /// Sets the relative log path for this server's stderr output.
    pub fn with_log_relative_path(mut self, log_relative_path: PathBuf) -> Self {
        self.log_relative_path = Some(log_relative_path);
        self
    }
    /// Returns the relative log path if configured.
    pub fn log_relative_path(&self) -> Option<&PathBuf> {
        self.log_relative_path.as_ref()
    }

    /// Returns the initial workspace path.
    pub fn initial_workspace(&self) -> &Path {
        &self.initial_workspace
    }

    pub(crate) fn server_name(&self) -> String {
        self.server_type.binary_name().to_string()
    }

    pub(crate) fn languages(&self) -> Vec<LanguageId> {
        self.server_type.languages()
    }

    /// Creates the command and init params for the LSP server.
    ///
    /// PATH takes precedence over custom installations. If the binary is available
    /// and working on PATH, we use that. Otherwise, we fall back to our custom installation.
    #[cfg(not(target_arch = "wasm32"))]
    pub(crate) async fn command_and_params(self) -> Result<ResolvedLspCommand> {
        // Resolve the effective PATH for this server. We try multiple sources:
        // 1. The PATH passed from the terminal session
        // 2. PATH captured from the user's interactive login shell (picks up nvm, fnm, volta, etc.)
        let executor = self.resolve_effective_executor().await;

        let is_working_on_path = self
            .server_type
            .is_working_on_path(&executor, self.client.clone())
            .await;

        let custom_binary_config = if is_working_on_path {
            None
        } else {
            self.server_type
                .find_installed_binary_config(executor.path_env_var())
                .await
        };

        if !is_working_on_path && custom_binary_config.is_none() {
            anyhow::bail!(
                "{} is not installed. Binary was not found on PATH and no custom installation exists",
                self.server_type.binary_name()
            );
        }

        let mut command = self
            .server_type
            .create_command(custom_binary_config.clone(), &executor);

        // Set the working directory to the workspace root. This is required for
        // LSP servers like rust-analyzer to properly discover the project structure.
        command.current_dir(&self.initial_workspace);

        log::info!(
            "LSP {} starting with custom_binary_config: {:?}",
            self.server_type.binary_name(),
            custom_binary_config
        );

        let params = default_init_params(&self.initial_workspace, self.client_name)?;

        Ok(ResolvedLspCommand { command, params })
    }

    /// Resolves the best available PATH for running LSP-related commands.
    /// Tries the session PATH first, then falls back to capturing PATH from
    /// the user's interactive login shell (which includes nvm, fnm, volta, pyenv, etc.).
    #[cfg(not(target_arch = "wasm32"))]
    async fn resolve_effective_executor(&self) -> crate::CommandBuilder {
        // If we have a session PATH, check if it can at least find common tools
        if let Some(ref path) = self.path_env_var {
            if !path.is_empty() {
                // Quick sanity check: can this PATH find the LSP binary or node?
                let executor = crate::CommandBuilder::new(Some(path.clone()));
                let works = self
                    .server_type
                    .is_working_on_path(&executor, self.client.clone())
                    .await;
                if works {
                    return executor;
                }
            }
        }

        // Session PATH didn't work — try interactive shell PATH
        if let Some(shell_path) = crate::CommandBuilder::capture_interactive_shell_path().await {
            log::info!(
                "Using interactive shell PATH for {} (session PATH insufficient)",
                self.server_type.binary_name()
            );
            return crate::CommandBuilder::new(Some(shell_path));
        }

        // Fall back to whatever we have
        crate::CommandBuilder::new(self.path_env_var.clone())
    }

    pub(crate) fn server_type(&self) -> LSPServerType {
        self.server_type
    }
}

pub(crate) fn path_to_lsp_uri(path: &Path) -> Result<Uri> {
    if !path.is_absolute() {
        return Err(anyhow::anyhow!("Path must be absolute: {}", path.display()));
    }

    // url::Url::from_file_path handles percent-encoding internally but is not
    // available on WASM. LSP is not supported on WASM either, so the fallback
    // is a simple string concatenation.
    #[cfg(not(target_arch = "wasm32"))]
    {
        let url = url::Url::from_file_path(path).map_err(|()| {
            anyhow::anyhow!("Failed to convert path to file URI: {}", path.display())
        })?;

        // The url crate doesn't encode brackets, but LSP requires them to be
        // percent-encoded (e.g. Next.js [slug].tsx routes).
        let uri_str = url.as_str().replace('[', "%5B").replace(']', "%5D");

        uri_str.parse::<Uri>().map_err(anyhow::Error::from)
    }

    #[cfg(target_arch = "wasm32")]
    {
        let path_str = path.to_string_lossy();
        let uri_string = format!("file://{path_str}");
        uri_string.parse::<Uri>().map_err(anyhow::Error::from)
    }
}

pub(crate) fn lsp_uri_to_path(uri: &Uri) -> Result<PathBuf> {
    // Validate this is a file URI
    let scheme = uri.scheme().map(|s| s.as_str());
    if scheme != Some("file") {
        return Err(anyhow::anyhow!("Invalid file URI: {}", uri.as_str()));
    }

    // Decode percent-encoded characters (e.g., %40 -> @)
    // This is necessary because LSP servers return URL-encoded paths
    let decoded_path = uri
        .path()
        .as_estr()
        .decode()
        .into_string()
        .map_err(|e| anyhow::anyhow!("Invalid UTF-8 in URI path: {e}"))?;

    let mut path_str: &str = decoded_path.as_ref();

    // Windows URIs are formatted like: file:///C:/path/to/file
    // The path component is `/C:/path/to/file`, strip the leading slash.
    if cfg!(windows) {
        path_str = path_str.strip_prefix('/').unwrap_or(path_str);
        return Ok(PathBuf::from(path_str.replace('/', "\\")));
    }

    Ok(PathBuf::from(path_str))
}

fn path_to_workspace_folder(path: &Path) -> Result<WorkspaceFolder> {
    path_to_lsp_uri(path).map(|url| WorkspaceFolder {
        uri: url,
        name: path
            .file_name()
            .unwrap_or_default()
            .to_string_lossy()
            .to_string(),
    })
}

fn default_client_capabilities() -> ClientCapabilities {
    ClientCapabilities {
        workspace: Some(WorkspaceClientCapabilities {
            did_change_watched_files: Option::from(DidChangeWatchedFilesClientCapabilities {
                dynamic_registration: Some(true),
                relative_pattern_support: Some(true),
            }),
            ..Default::default()
        }),
        window: Some(WindowClientCapabilities {
            work_done_progress: Some(true),
            ..Default::default()
        }),
        text_document: Some(TextDocumentClientCapabilities {
            synchronization: Some(TextDocumentSyncClientCapabilities {
                dynamic_registration: Some(true),
                will_save: Some(false),
                will_save_wait_until: Some(false),
                did_save: Some(true),
            }),
            completion: Some(CompletionClientCapabilities {
                dynamic_registration: Some(false),
                completion_item: Some(CompletionItemCapability {
                    snippet_support: Some(true),
                    documentation_format: Some(vec![MarkupKind::Markdown, MarkupKind::PlainText]),
                    resolve_support: Some(CompletionItemCapabilityResolveSupport {
                        properties: vec![
                            "documentation".into(),
                            "detail".into(),
                            "additionalTextEdits".into(),
                        ],
                    }),
                    ..Default::default()
                }),
                ..Default::default()
            }),
            definition: Some(GotoCapability {
                dynamic_registration: Some(false),
                link_support: Some(true),
            }),
            hover: Some(HoverClientCapabilities {
                dynamic_registration: Some(false),
                content_format: Some(vec![MarkupKind::Markdown, MarkupKind::PlainText]),
            }),
            publish_diagnostics: Some(PublishDiagnosticsClientCapabilities {
                version_support: Some(true),
                related_information: Some(true),
                ..Default::default()
            }),
            signature_help: Some(SignatureHelpClientCapabilities {
                dynamic_registration: Some(false),
                ..Default::default()
            }),
            rename: Some(RenameClientCapabilities {
                dynamic_registration: Some(false),
                prepare_support: Some(true),
                ..Default::default()
            }),
            code_action: Some(CodeActionClientCapabilities {
                dynamic_registration: Some(false),
                ..Default::default()
            }),
            ..Default::default()
        }),
        ..Default::default()
    }
}

pub fn default_init_params(workspace_uri: &Path, client_name: String) -> Result<InitializeParams> {
    let workspace_folder = path_to_workspace_folder(workspace_uri)?;

    Ok(InitializeParams {
        process_id: Some(std::process::id()),
        capabilities: default_client_capabilities(),
        workspace_folders: Some(vec![workspace_folder]),
        client_info: Some(ClientInfo {
            name: client_name,
            version: option_env!("GIT_RELEASE_TAG").map(|s| s.to_string()),
        }),
        locale: None,
        work_done_progress_params: WorkDoneProgressParams::default(),
        ..Default::default()
    })
}

#[cfg(test)]
#[path = "config_tests.rs"]
mod tests;