zesdex/src/tool/lsp/mod.rs

#![allow(clippy::cast_possible_truncation, clippy::cast_sign_loss, clippy::cast_precision_loss, clippy::cast_possible_wrap)]
use std::fmt::Write;
use serde_json::{json, Value};
use anyhow::{Result, anyhow};

use crate::tool::{Tool, ToolCtx};
use crate::app::lsp::path_to_lsp_uri;

pub struct LspConnect;

impl Tool for LspConnect {
    fn name(&self) -> &'static str {
        "lsp_connect"
    }

    fn description(&self) -> &'static str {
        "Connect to a Language Server Protocol (LSP) server for a programming language. \
         Known file extensions for the language are auto-registered, enabling other lsp_* \
         tools to auto-detect this server when `server` is omitted."
    }

    fn parameters(&self) -> Value {
        json!({
            "type": "object",
            "properties": {
                "name": {
                    "type": "string",
                    "description": "Short name for this LSP connection (e.g. 'rust', 'typescript')"
                },
                "command": {
                    "type": "string",
                    "description": "The LSP server binary to spawn (e.g. 'rust-analyzer', 'typescript-language-server')"
                },
                "args": {
                    "type": "array",
                    "items": { "type": "string" },
                    "description": "Command-line arguments for the LSP server"
                },
                "language_id": {
                    "type": "string",
                    "description": "Language identifier (e.g. 'rust', 'typescript', 'python')"
                }
            },
            "required": ["name", "command", "language_id"]
        })
    }

    fn run(&self, ctx: &ToolCtx, args: &Value) -> Result<String> {
        let name = args.get("name")
            .and_then(|v| v.as_str())
            .ok_or_else(|| anyhow!("missing required argument: name"))?;
        let command = args.get("command")
            .and_then(|v| v.as_str())
            .ok_or_else(|| anyhow!("missing required argument: command"))?;
        let language_id = args.get("language_id")
            .and_then(|v| v.as_str())
            .ok_or_else(|| anyhow!("missing required argument: language_id"))?;
        let extra_args: Vec<String> = args.get("args")
            .and_then(|v| v.as_array())
            .map(|arr| arr.iter().filter_map(|v| v.as_str().map(String::from)).collect())
            .unwrap_or_default();

        let mut manager = ctx.lsp_manager.lock()
            .map_err(|e| anyhow!("LSP manager lock error: {e}"))?;
        manager.connect(name, command, &extra_args, language_id)?;

        // Auto-register this server's known extensions so lsp_diagnostics /
        // lsp_hover / lsp_completion / lsp_definition / lsp_references can
        // auto-detect it later without an explicit `server` argument.
        let known_exts = known_extensions_for(language_id);
        if !known_exts.is_empty() {
            manager.register_extensions(name, known_exts);
        }

        let client_arc = manager.get_client(name);
        let caps = client_arc.and_then(|c| {
            c.lock().ok().map(|guard| guard.server_capabilities().clone())
        }).unwrap_or_default();

        let caps_summary = serde_json::to_string_pretty(&caps)
            .unwrap_or_else(|_| "{}".to_string());

        Ok(format!(
            "Connected to LSP server '{name}' (language: {language_id})\nServer capabilities:\n{caps_summary}"
        ))
    }
}

pub struct LspDiagnostics;

impl Tool for LspDiagnostics {
    fn name(&self) -> &'static str {
        "lsp_diagnostics"
    }

    fn description(&self) -> &'static str {
        "Get diagnostics (errors, warnings, hints) for a file from an LSP server. \
         `server` is optional — if omitted, the server is auto-detected from the file's extension."
    }

    fn parameters(&self) -> Value {
        json!({
            "type": "object",
            "properties": {
                "server": {
                    "type": "string",
                    "description": "Name of the connected LSP server. Optional — auto-detected from the file extension if omitted."
                },
                "path": {
                    "type": "string",
                    "description": "Path to the file to analyze (relative to workspace root)"
                },
                "text": {
                    "type": "string",
                    "description": "The full text content of the file"
                }
            },
            "required": ["path", "text"]
        })
    }

    fn run(&self, ctx: &ToolCtx, args: &Value) -> Result<String> {
        let rel_path = args.get("path")
            .and_then(|v| v.as_str())
            .ok_or_else(|| anyhow!("missing required argument: path"))?;
        let text = args.get("text")
            .and_then(|v| v.as_str())
            .ok_or_else(|| anyhow!("missing required argument: text"))?;
        let server_name = resolve_server_name(ctx, args, rel_path)?;
        let server_name = server_name.as_str();

        let abs_path = crate::tool::resolve_path(&ctx.workspaces, rel_path)?;
        let uri = path_to_lsp_uri(&abs_path.to_string_lossy());

        let manager = ctx.lsp_manager.lock()
            .map_err(|e| anyhow!("LSP manager lock error: {e}"))?;
        let language_id = manager.get_language_id(server_name)
            .ok_or_else(|| anyhow!("LSP server '{server_name}' not found. Use lsp_connect first."))?;
        let client_arc = manager.get_client(server_name)
            .ok_or_else(|| anyhow!("LSP server '{server_name}' not found"))?;
        drop(manager);

        let mut client = client_arc.lock()
            .map_err(|e| anyhow!("LSP client lock error: {e}"))?;

        match client.collect_diagnostics(&uri, &language_id, text) {
            Ok(diags) => {
                let diags_array = diags.as_array().cloned().unwrap_or_default();
                if diags_array.is_empty() {
                    return Ok("No diagnostics found for this file.".to_string());
                }
                let mut output = String::from("Diagnostics:\n");
                for d in &diags_array {
                    let range = d.get("range").and_then(|r| r.get("start"));
                    let severity = match d.get("severity").and_then(serde_json::Value::as_i64).unwrap_or(0) {
                        1 => "ERROR",
                        2 => "WARNING",
                        3 => "INFO",
                        4 => "HINT",
                        _ => "NOTE",
                    };
                    let message = d.get("message").and_then(|m| m.as_str()).unwrap_or("?");
                    let line = range.and_then(|r| r.get("line")).and_then(serde_json::Value::as_i64).unwrap_or(0);
                    let col = range.and_then(|r| r.get("character")).and_then(serde_json::Value::as_i64).unwrap_or(0);
                    let code = d.get("code")
                        .and_then(|c| c.as_str().or_else(|| c.as_i64().map(|n| Box::leak(Box::new(n.to_string()))).map(|s| s.as_str())))
                        .unwrap_or("");
                    let code_str = if code.is_empty() { String::new() } else { format!(" [{code}]") };
                    writeln!(output, "  {}:{}:{} - {}{}: {}", rel_path, line + 1, col, severity, code_str, message).unwrap();
                }
                Ok(output)
            }
            Err(e) => {
                if e.to_string().contains("timed out") {
                    Ok("Diagnostics request timed out. The server may still be initializing. Try again in a moment.".to_string())
                } else {
                    Err(e)
                }
            }
        }
    }
}

pub struct LspHover;

impl Tool for LspHover {
    fn name(&self) -> &'static str {
        "lsp_hover"
    }

    fn description(&self) -> &'static str {
        "Get hover information (type signature, documentation) at a cursor position in a file. \
         `server` is optional — if omitted, the server is auto-detected from the file's extension."
    }

    fn parameters(&self) -> Value {
        json!({
            "type": "object",
            "properties": {
                "server": {
                    "type": "string",
                    "description": "Name of the connected LSP server. Optional — auto-detected from the file extension if omitted."
                },
                "path": {
                    "type": "string",
                    "description": "Path to the file (relative to workspace root)"
                },
                "line": {
                    "type": "integer",
                    "description": "Line number (0-based)"
                },
                "column": {
                    "type": "integer",
                    "description": "Column number (0-based)"
                },
                "language_id": {
                    "type": "string",
                    "description": "Language identifier (e.g. 'rust', 'typescript'). Optional if already set via lsp_connect."
                }
            },
            "required": ["path", "line", "column"]
        })
    }

    fn run(&self, ctx: &ToolCtx, args: &Value) -> Result<String> {
        let rel_path = args.get("path")
            .and_then(|v| v.as_str())
            .ok_or_else(|| anyhow!("missing required argument: path"))?;
        let line = args.get("line")
            .and_then(serde_json::Value::as_i64)
            .ok_or_else(|| anyhow!("missing required argument: line"))? as u32;
        let column = args.get("column")
            .and_then(serde_json::Value::as_i64)
            .ok_or_else(|| anyhow!("missing required argument: column"))? as u32;
        let server_name = resolve_server_name(ctx, args, rel_path)?;
        let server_name = server_name.as_str();

        let abs_path = crate::tool::resolve_path(&ctx.workspaces, rel_path)?;
        let uri = path_to_lsp_uri(&abs_path.to_string_lossy());

        let file_content = std::fs::read_to_string(&abs_path)
            .map_err(|e| anyhow!("failed to read file '{rel_path}': {e}"))?;

        let manager = ctx.lsp_manager.lock()
            .map_err(|e| anyhow!("LSP manager lock error: {e}"))?;
        let language_id = manager.get_language_id(server_name)
            .unwrap_or_else(|| {
                args.get("language_id").and_then(|v| v.as_str()).unwrap_or("plaintext").to_string()
            });
        let client_arc = manager.get_client(server_name)
            .ok_or_else(|| anyhow!("LSP server '{server_name}' not found. Use lsp_connect first."))?;
        drop(manager);

        let mut client = client_arc.lock()
            .map_err(|e| anyhow!("LSP client lock error: {e}"))?;

        client.did_open(&uri, &language_id, 1, &file_content)?;
        let result = client.hover(&uri, line, column);
        let _ = client.did_close(&uri);

        match result {
            Ok(hover_result) => {
                if hover_result == Value::Null {
                    return Ok("No hover information available at this position.".to_string());
                }
                let contents = hover_result.get("contents");
                let range = hover_result.get("range");
                let mut output = String::new();
                if let Some(range_val) = range {
                    if let Some(start) = range_val.get("start") {
                        let rl = start.get("line").and_then(serde_json::Value::as_i64).unwrap_or(0);
                        let rc = start.get("character").and_then(serde_json::Value::as_i64).unwrap_or(0);
                        writeln!(output, "Range: {}:{}", rl + 1, rc + 1).unwrap();
                    }
                }
                if let Some(contents_val) = contents {
                    output.push_str(&format_hover_contents(contents_val));
                } else {
                    output.push_str(&serde_json::to_string_pretty(&hover_result).unwrap_or_default());
                }
                Ok(output)
            }
            Err(e) => Err(e),
        }
    }
}

fn format_hover_contents(contents: &Value) -> String {
    let mut out = String::new();
    match contents {
        Value::String(s) => {
            out.push_str(s);
        }
        Value::Object(map) => {
            if let Some(kind) = map.get("kind").and_then(|k| k.as_str()) {
                write!(out, "[{kind}] ").unwrap();
            }
            if let Some(value) = map.get("value").and_then(|v| v.as_str()) {
                out.push_str(value);
            }
        }
        Value::Array(arr) => {
            for (i, item) in arr.iter().enumerate() {
                if i > 0 {
                    out.push('\n');
                }
                out.push_str(&format_hover_contents(item));
            }
        }
        _ => {
            out.push_str(&serde_json::to_string_pretty(contents).unwrap_or_default());
        }
    }
    out
}

pub struct LspCompletion;

impl Tool for LspCompletion {
    fn name(&self) -> &'static str {
        "lsp_completion"
    }

    fn description(&self) -> &'static str {
        "Get code completion suggestions at a cursor position from an LSP server. \
         `server` is optional — if omitted, the server is auto-detected from the file's extension."
    }

    fn parameters(&self) -> Value {
        json!({
            "type": "object",
            "properties": {
                "server": {
                    "type": "string",
                    "description": "Name of the connected LSP server. Optional — auto-detected from the file extension if omitted."
                },
                "path": {
                    "type": "string",
                    "description": "Path to the file (relative to workspace root)"
                },
                "line": {
                    "type": "integer",
                    "description": "Line number (0-based)"
                },
                "column": {
                    "type": "integer",
                    "description": "Column number (0-based)"
                }
            },
            "required": ["path", "line", "column"]
        })
    }

    fn run(&self, ctx: &ToolCtx, args: &Value) -> Result<String> {
        let rel_path = args.get("path")
            .and_then(|v| v.as_str())
            .ok_or_else(|| anyhow!("missing required argument: path"))?;
        let line = args.get("line")
            .and_then(serde_json::Value::as_i64)
            .ok_or_else(|| anyhow!("missing required argument: line"))? as u32;
        let column = args.get("column")
            .and_then(serde_json::Value::as_i64)
            .ok_or_else(|| anyhow!("missing required argument: column"))? as u32;
        let server_name = resolve_server_name(ctx, args, rel_path)?;
        let server_name = server_name.as_str();

        let abs_path = crate::tool::resolve_path(&ctx.workspaces, rel_path)?;
        let uri = path_to_lsp_uri(&abs_path.to_string_lossy());

        let file_content = std::fs::read_to_string(&abs_path)
            .map_err(|e| anyhow!("failed to read file '{rel_path}': {e}"))?;

        let manager = ctx.lsp_manager.lock()
            .map_err(|e| anyhow!("LSP manager lock error: {e}"))?;
        let language_id = manager.get_language_id(server_name)
            .unwrap_or_else(|| "plaintext".to_string());
        let client_arc = manager.get_client(server_name)
            .ok_or_else(|| anyhow!("LSP server '{server_name}' not found. Use lsp_connect first."))?;
        drop(manager);

        let mut client = client_arc.lock()
            .map_err(|e| anyhow!("LSP client lock error: {e}"))?;

        client.did_open(&uri, &language_id, 1, &file_content)?;
        let result = client.completion(&uri, line, column);
        let _ = client.did_close(&uri);

        match result {
            Ok(completion_result) => {
                let items = if let Some(items) = completion_result.as_array() {
                    items.clone()
                } else if let Some(arr) = completion_result.get("items").and_then(|v| v.as_array()) {
                    arr.clone()
                } else {
                    Vec::new()
                };

                if items.is_empty() {
                    return Ok("No completions available at this position.".to_string());
                }

                let mut output = format!("{} completion suggestions at {}:{}:\n", items.len(), line + 1, column + 1);
                for (i, item) in items.iter().enumerate().take(50) {
                    let label = item.get("label").and_then(|l| l.as_str()).unwrap_or("?");
                    let kind = match item.get("kind").and_then(serde_json::Value::as_i64).unwrap_or(0) {
                        1 => "Text",
                        2 => "Method",
                        3 => "Function",
                        4 => "Constructor",
                        5 => "Field",
                        6 => "Variable",
                        7 => "Class",
                        8 => "Interface",
                        9 => "Module",
                        10 => "Property",
                        11 => "Unit",
                        12 => "Value",
                        13 => "Enum",
                        14 => "Keyword",
                        15 => "Snippet",
                        16 => "Color",
                        17 => "File",
                        18 => "Reference",
                        19 => "Folder",
                        20 => "EnumMember",
                        21 => "Constant",
                        22 => "Struct",
                        23 => "Event",
                        24 => "Operator",
                        25 => "TypeParameter",
                        _ => "Other",
                    };
                    let detail = item.get("detail").and_then(|d| d.as_str()).unwrap_or("");
                    let detail_str = if detail.is_empty() { String::new() } else { format!(" - {detail}") };
                    writeln!(output, "  {}. [{}] {}{}", i + 1, kind, label, detail_str).unwrap();
                }
                if items.len() > 50 {
                    writeln!(output, "  ... and {} more", items.len() - 50).unwrap();
                }
                Ok(output)
            }
            Err(e) => Err(e),
        }
    }
}

pub struct LspDefinition;

impl Tool for LspDefinition {
    fn name(&self) -> &'static str {
        "lsp_definition"
    }

    fn description(&self) -> &'static str {
        "Go to definition: find the location where a symbol is defined. \
         `server` is optional — if omitted, the server is auto-detected from the file's extension."
    }

    fn parameters(&self) -> Value {
        json!({
            "type": "object",
            "properties": {
                "server": {
                    "type": "string",
                    "description": "Name of the connected LSP server. Optional — auto-detected from the file extension if omitted."
                },
                "path": {
                    "type": "string",
                    "description": "Path to the file (relative to workspace root)"
                },
                "line": {
                    "type": "integer",
                    "description": "Line number (0-based)"
                },
                "column": {
                    "type": "integer",
                    "description": "Column number (0-based)"
                }
            },
            "required": ["path", "line", "column"]
        })
    }

    fn run(&self, ctx: &ToolCtx, args: &Value) -> Result<String> {
        let rel_path = args.get("path")
            .and_then(|v| v.as_str())
            .ok_or_else(|| anyhow!("missing required argument: path"))?;
        let line = args.get("line")
            .and_then(serde_json::Value::as_i64)
            .ok_or_else(|| anyhow!("missing required argument: line"))? as u32;
        let column = args.get("column")
            .and_then(serde_json::Value::as_i64)
            .ok_or_else(|| anyhow!("missing required argument: column"))? as u32;
        let server_name = resolve_server_name(ctx, args, rel_path)?;
        let server_name = server_name.as_str();

        let abs_path = crate::tool::resolve_path(&ctx.workspaces, rel_path)?;
        let uri = path_to_lsp_uri(&abs_path.to_string_lossy());

        let file_content = std::fs::read_to_string(&abs_path)
            .map_err(|e| anyhow!("failed to read file '{rel_path}': {e}"))?;

        let manager = ctx.lsp_manager.lock()
            .map_err(|e| anyhow!("LSP manager lock error: {e}"))?;
        let language_id = manager.get_language_id(server_name)
            .unwrap_or_else(|| "plaintext".to_string());
        let client_arc = manager.get_client(server_name)
            .ok_or_else(|| anyhow!("LSP server '{server_name}' not found. Use lsp_connect first."))?;
        drop(manager);

        let mut client = client_arc.lock()
            .map_err(|e| anyhow!("LSP client lock error: {e}"))?;

        client.did_open(&uri, &language_id, 1, &file_content)?;
        let result = client.goto_definition(&uri, line, column);
        let _ = client.did_close(&uri);

        match result {
            Ok(def_result) => {
                if def_result == Value::Null {
                    return Ok("No definition found at this position.".to_string());
                }
                let locations = if let Some(loc) = def_result.as_array() {
                    loc.clone()
                } else {
                    vec![def_result.clone()]
                };

                if locations.is_empty() {
                    return Ok("No definition found.".to_string());
                }

                let mut output = String::from("Definition(s):\n");
                for (i, loc) in locations.iter().enumerate().take(10) {
                    let target_uri = loc.get("uri").and_then(|u| u.as_str()).unwrap_or("?");
                    let target_range = loc.get("range").or_else(|| loc.get("targetRange"));
                    let target_start = target_range.and_then(|r| r.get("start"));
                    let tl = target_start.and_then(|s| s.get("line")).and_then(serde_json::Value::as_i64).unwrap_or(0);
                    let tc = target_start.and_then(|s| s.get("character")).and_then(serde_json::Value::as_i64).unwrap_or(0);
                    let path_str = target_uri.strip_prefix("file://").unwrap_or(target_uri);
                    writeln!(output, "  {}. {}:{}:{}", i + 1, path_str, tl + 1, tc + 1).unwrap();
                }
                if locations.len() > 10 {
                    writeln!(output, "  ... and {} more", locations.len() - 10).unwrap();
                }
                Ok(output)
            }
            Err(e) => Err(e),
        }
    }
}

pub struct LspReferences;

impl Tool for LspReferences {
    fn name(&self) -> &'static str {
        "lsp_references"
    }

    fn description(&self) -> &'static str {
        "Find all references to a symbol at a cursor position. \
         `server` is optional — if omitted, the server is auto-detected from the file's extension."
    }

    fn parameters(&self) -> Value {
        json!({
            "type": "object",
            "properties": {
                "server": {
                    "type": "string",
                    "description": "Name of the connected LSP server. Optional — auto-detected from the file extension if omitted."
                },
                "path": {
                    "type": "string",
                    "description": "Path to the file (relative to workspace root)"
                },
                "line": {
                    "type": "integer",
                    "description": "Line number (0-based)"
                },
                "column": {
                    "type": "integer",
                    "description": "Column number (0-based)"
                }
            },
            "required": ["path", "line", "column"]
        })
    }

    fn run(&self, ctx: &ToolCtx, args: &Value) -> Result<String> {
        let rel_path = args.get("path")
            .and_then(|v| v.as_str())
            .ok_or_else(|| anyhow!("missing required argument: path"))?;
        let line = args.get("line")
            .and_then(serde_json::Value::as_i64)
            .ok_or_else(|| anyhow!("missing required argument: line"))? as u32;
        let column = args.get("column")
            .and_then(serde_json::Value::as_i64)
            .ok_or_else(|| anyhow!("missing required argument: column"))? as u32;
        let server_name = resolve_server_name(ctx, args, rel_path)?;
        let server_name = server_name.as_str();

        let abs_path = crate::tool::resolve_path(&ctx.workspaces, rel_path)?;
        let uri = path_to_lsp_uri(&abs_path.to_string_lossy());

        let file_content = std::fs::read_to_string(&abs_path)
            .map_err(|e| anyhow!("failed to read file '{rel_path}': {e}"))?;

        let manager = ctx.lsp_manager.lock()
            .map_err(|e| anyhow!("LSP manager lock error: {e}"))?;
        let language_id = manager.get_language_id(server_name)
            .unwrap_or_else(|| "plaintext".to_string());
        let client_arc = manager.get_client(server_name)
            .ok_or_else(|| anyhow!("LSP server '{server_name}' not found. Use lsp_connect first."))?;
        drop(manager);

        let mut client = client_arc.lock()
            .map_err(|e| anyhow!("LSP client lock error: {e}"))?;

        client.did_open(&uri, &language_id, 1, &file_content)?;
        let result = client.references(&uri, line, column);
        let _ = client.did_close(&uri);

        match result {
            Ok(ref_result) => {
                let locations = ref_result.as_array().cloned().unwrap_or_default();
                if locations.is_empty() {
                    return Ok("No references found for this symbol.".to_string());
                }

                let mut output = format!("{} reference(s) found:\n", locations.len());
                for (i, loc) in locations.iter().enumerate().take(50) {
                    let target_uri = loc.get("uri").and_then(|u| u.as_str()).unwrap_or("?");
                    let range = loc.get("range").and_then(|r| r.get("start"));
                    let rl = range.and_then(|s| s.get("line")).and_then(serde_json::Value::as_i64).unwrap_or(0);
                    let rc = range.and_then(|s| s.get("character")).and_then(serde_json::Value::as_i64).unwrap_or(0);
                    let path_str = target_uri.strip_prefix("file://").unwrap_or(target_uri);
                    writeln!(output, "  {}. {}:{}:{}", i + 1, path_str, rl + 1, rc + 1).unwrap();
                }
                if locations.len() > 50 {
                    writeln!(output, "  ... and {} more references", locations.len() - 50).unwrap();
                }
                Ok(output)
            }
            Err(e) => Err(e),
        }
    }
}

pub struct LspDisconnect;

impl Tool for LspDisconnect {
    fn name(&self) -> &'static str {
        "lsp_disconnect"
    }

    fn description(&self) -> &'static str {
        "Disconnect from a running LSP server and release its resources"
    }

    fn parameters(&self) -> Value {
        json!({
            "type": "object",
            "properties": {
                "name": {
                    "type": "string",
                    "description": "Name of the LSP server to disconnect"
                }
            },
            "required": ["name"]
        })
    }

    fn run(&self, ctx: &ToolCtx, args: &Value) -> Result<String> {
        let name = args.get("name")
            .and_then(|v| v.as_str())
            .ok_or_else(|| anyhow!("missing required argument: name"))?;

        let mut manager = ctx.lsp_manager.lock()
            .map_err(|e| anyhow!("LSP manager lock error: {e}"))?;

        if manager.disconnect(name) {
            Ok(format!("Disconnected from LSP server '{name}'"))
        } else {
            Err(anyhow!("LSP server '{name}' not found"))
        }
    }
}

/// Return the default file extensions associated with a language id.
///
/// Flow: pure `match` on `language_id` -> static slice of extension
/// strings (with leading dot). Returns an empty slice for unknown
/// languages, so callers can safely chain lookups without a special case.
///
/// Used by `lsp_connect` to auto-register extensions for a newly connected
/// server, and by `auto_detect_server` as a fallback when the manager's own
/// `extension_registry` has no entry yet.
fn known_extensions_for(language_id: &str) -> &[&'static str] {
    match language_id {
        "rust" => &[".rs"],
        "typescript" => &[".ts", ".tsx", ".js", ".jsx"],
        "go" => &[".go"],
        "java" => &[".java"],
        _ => &[],
    }
}

/// Guess which connected LSP server should handle `path` based on its extension.
///
/// Flow: extract extension from `path` -> for each connected server, check
/// whether `known_extensions_for(server.language_id)` contains the extension
/// -> return the first match's name.
///
/// This is a fallback used only when the caller omits `server` and the file's
/// extension is not (yet) present in `LspManager::extension_registry` — e.g.
/// a server connected without an explicit `register_extensions` call. Returns
/// `None` if the path has no extension, the lock is poisoned, or no
/// connected server's language is known to use that extension.
fn auto_detect_server(ctx: &ToolCtx, path: &str) -> Option<String> {
    let ext = std::path::Path::new(path).extension().and_then(|e| e.to_str())?;
    let dot_ext = format!(".{ext}");
    if let Ok(mgr) = ctx.lsp_manager.lock() {
        for s in &mgr.servers {
            let exts = known_extensions_for(&s.language_id);
            if exts.contains(&dot_ext.as_str()) {
                return Some(s.name.clone());
            }
        }
    }
    None
}

/// Resolve the LSP server name to use for a tool call: explicit `server`
/// argument if present, otherwise auto-detected from `path`'s extension.
///
/// Flow: `args["server"]` present -> use it as-is. Otherwise -> try
/// `LspManager::find_server_for_path`-style registry lookup by delegating to
/// `auto_detect_server`. If that also fails, build a helpful error message
/// listing the currently connected servers (via `LspManager::list_servers`)
/// so the caller knows whether to connect one first.
///
/// Return: `Ok(server_name)` on success. `Err` only when no `server` was
/// given and auto-detection could not resolve one — never fails just
/// because the caller provided an explicit (possibly wrong) server name,
/// since downstream `get_client`/`get_language_id` calls report that error.
fn resolve_server_name(ctx: &ToolCtx, args: &Value, path: &str) -> Result<String> {
    if let Some(server) = args.get("server").and_then(|v| v.as_str()) {
        return Ok(server.to_string());
    }

    if let Some(name) = auto_detect_server(ctx, path) {
        return Ok(name);
    }

    let ext = std::path::Path::new(path)
        .extension()
        .and_then(|e| e.to_str()).map_or_else(|| "<none>".to_string(), |e| format!(".{e}"));

    let available = ctx.lsp_manager.lock().ok()
        .map(|mgr| {
            mgr.list_servers()
                .iter()
                .map(|(name, lang, _)| format!("{name} ({lang})"))
                .collect::<Vec<_>>()
                .join(", ")
        })
        .unwrap_or_default();
    let available = if available.is_empty() { "none".to_string() } else { available };

    Err(anyhow!(
        "LSP server not found for extension '{ext}'. Use lsp_connect to connect one. Available servers: {available}"
    ))
}