use std::path::Path;

use async_trait::async_trait;
use serde_json::json;

use crate::text::take_prefix_chars;
use crate::tools::traits::{Tool, ToolResult};
use crate::tools::extract_u64;

const MAX_CHARS: usize = 100_000;
const DEFAULT_LIMIT: usize = 2000;

pub struct FileReadTool {
    allowed_dir: Option<String>,
}

impl FileReadTool {
    pub fn new() -> Self {
        Self { allowed_dir: None }
    }

    pub fn with_allowed_dir(dir: String) -> Self {
        Self {
            allowed_dir: Some(dir),
        }
    }

    fn resolve_path(&self, path: &str) -> Result<std::path::PathBuf, String> {
        let p = Path::new(path);
        let resolved = if p.is_absolute() {
            p.to_path_buf()
        } else {
            std::env::current_dir()
                .map_err(|e| format!("Failed to get current directory: {}", e))?
                .join(p)
        };

        // Check directory restriction
        if let Some(ref allowed) = self.allowed_dir {
            let allowed_path = Path::new(allowed);
            if !resolved.starts_with(allowed_path) {
                return Err(format!(
                    "Path '{}' is outside allowed directory '{}'",
                    path, allowed
                ));
            }
        }

        Ok(resolved)
    }
}

impl Default for FileReadTool {
    fn default() -> Self {
        Self::new()
    }
}

#[async_trait]
impl Tool for FileReadTool {
    fn name(&self) -> &str {
        "read"
    }

    fn description(&self) -> &str {
        "Read the contents of a file. Returns numbered lines. Use offset and limit to paginate through large files."
    }

    fn parameters_schema(&self) -> serde_json::Value {
        json!({
            "type": "object",
            "properties": {
                "path": {
                    "type": "string",
                    "description": "The file path to read"
                },
                "offset": {
                    "type": "integer",
                    "description": "Line number to start reading from (1-indexed, default 1)",
                    "minimum": 1
                },
                "limit": {
                    "type": "integer",
                    "description": "Maximum number of lines to read (default 2000)",
                    "minimum": 1
                }
            },
            "required": ["path"]
        })
    }

    fn read_only(&self) -> bool {
        true
    }

    async fn execute(&self, args: serde_json::Value) -> anyhow::Result<ToolResult> {
        let path = match args.get("path").and_then(|v| v.as_str()) {
            Some(p) => p,
            None => {
                return Ok(ToolResult {
                    success: false,
                    output: String::new(),
                    error: Some("Missing required parameter: path".to_string()),
                });
            }
        };

        let offset = extract_u64(&args, "offset")
            .map(|v| v as usize)
            .unwrap_or(1);

        let limit = extract_u64(&args, "limit")
            .map(|v| v as usize)
            .unwrap_or(DEFAULT_LIMIT);

        let resolved = match self.resolve_path(path) {
            Ok(p) => p,
            Err(e) => {
                return Ok(ToolResult {
                    success: false,
                    output: String::new(),
                    error: Some(e),
                });
            }
        };

        if !resolved.exists() {
            return Ok(ToolResult {
                success: false,
                output: String::new(),
                error: Some(format!("File not found: {}", path)),
            });
        }

        if !resolved.is_file() {
            return Ok(ToolResult {
                success: false,
                output: String::new(),
                error: Some(format!("Not a file: {}", path)),
            });
        }

        // Try to read as text
        match std::fs::read_to_string(&resolved) {
            Ok(content) => {
                let all_lines: Vec<&str> = content.lines().collect();
                let total = all_lines.len();

                if offset < 1 {
                    return Ok(ToolResult {
                        success: false,
                        output: String::new(),
                        error: Some(format!("offset must be at least 1, got {}", offset)),
                    });
                }

                if offset > total {
                    return Ok(ToolResult {
                        success: false,
                        output: String::new(),
                        error: Some(format!(
                            "offset {} is beyond end of file ({} lines)",
                            offset, total
                        )),
                    });
                }

                let start = offset - 1;
                let end = std::cmp::min(start + limit, total);
                let lines: Vec<String> = all_lines[start..end]
                    .iter()
                    .enumerate()
                    .map(|(i, line)| format!("{}| {}", start + i + 1, line))
                    .collect();

                let mut result = lines.join("\n");

                // Truncate if too long
                if result.len() > MAX_CHARS {
                    let original_len = result.len();
                    let mut truncated_chars = 0;
                    let mut end_idx = 0;
                    for (i, line) in lines.iter().enumerate() {
                        truncated_chars += line.len() + 1;
                        if truncated_chars > MAX_CHARS {
                            end_idx = i;
                            break;
                        }
                        end_idx = i + 1;
                    }
                    if end_idx == 0 && !lines.is_empty() {
                        // First line alone exceeds MAX_CHARS — take its prefix
                        result = take_prefix_chars(&lines[0], MAX_CHARS.saturating_sub(100));
                    } else {
                        result = lines[..end_idx].join("\n");
                    }
                    let truncated_amount = original_len.saturating_sub(result.len());
                    result.push_str(&format!(
                        "\n\n... ({} chars truncated) ...",
                        truncated_amount
                    ));
                }

                if end < total {
                    result.push_str(&format!(
                        "\n\n(Showing lines {}-{} of {}. Use offset={} to continue.)",
                        offset,
                        end,
                        total,
                        end + 1
                    ));
                } else {
                    result.push_str(&format!("\n\n(End of file — {} lines total)", total));
                }

                Ok(ToolResult {
                    success: true,
                    output: result,
                    error: None,
                })
            }
            Err(e) => {
                // Try to read as binary and encode as base64
                match std::fs::read(&resolved) {
                    Ok(bytes) => {
                        use base64::{Engine, engine::general_purpose::STANDARD};
                        let encoded = STANDARD.encode(&bytes);
                        let mime = mime_guess::from_path(&resolved)
                            .first_or_octet_stream()
                            .to_string();
                        Ok(ToolResult {
                            success: true,
                            output: format!(
                                "(Binary file: {}, {} bytes, base64 encoded)\n{}",
                                mime,
                                bytes.len(),
                                encoded
                            ),
                            error: None,
                        })
                    }
                    Err(_) => Ok(ToolResult {
                        success: false,
                        output: String::new(),
                        error: Some(format!("Failed to read file: {}", e)),
                    }),
                }
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::io::Write;
    use tempfile::NamedTempFile;

    #[tokio::test]
    async fn test_read_simple_file() {
        let mut file = NamedTempFile::new().unwrap();
        writeln!(file, "Line 1").unwrap();
        writeln!(file, "Line 2").unwrap();
        writeln!(file, "Line 3").unwrap();

        let tool = FileReadTool::new();
        let result = tool
            .execute(json!({ "path": file.path().to_str().unwrap() }))
            .await
            .unwrap();

        assert!(result.success);
        assert!(result.output.contains("Line 1"));
        assert!(result.output.contains("Line 2"));
        assert!(result.output.contains("Line 3"));
    }

    #[tokio::test]
    async fn test_read_with_offset_limit() {
        let mut file = NamedTempFile::new().unwrap();
        for i in 1..=10 {
            writeln!(file, "Line {}", i).unwrap();
        }

        let tool = FileReadTool::new();
        let result = tool
            .execute(json!({
                "path": file.path().to_str().unwrap(),
                "offset": 3,
                "limit": 2
            }))
            .await
            .unwrap();

        assert!(result.success);
        assert!(result.output.contains("Line 3"));
        assert!(result.output.contains("Line 4"));
        assert!(!result.output.contains("Line 2"));
    }

    #[tokio::test]
    async fn test_file_not_found() {
        let tool = FileReadTool::new();
        let result = tool
            .execute(json!({ "path": "/nonexistent/file.txt" }))
            .await
            .unwrap();

        assert!(!result.success);
        assert!(result.error.unwrap().contains("not found"));
    }

    #[tokio::test]
    async fn test_is_directory() {
        let tool = FileReadTool::new();
        let result = tool.execute(json!({ "path": "." })).await.unwrap();

        assert!(!result.success);
        assert!(result.error.unwrap().contains("Not a file"));
    }

    #[tokio::test]
    async fn test_read_single_long_line() {
        let mut file = NamedTempFile::new().unwrap();
        // Write a single line longer than MAX_CHARS
        let long_line = "A".repeat(150_000);
        file.write_all(long_line.as_bytes()).unwrap();

        let tool = FileReadTool::new();
        let result = tool
            .execute(json!({ "path": file.path().to_str().unwrap() }))
            .await
            .unwrap();

        assert!(result.success);
        // Should contain the line number prefix and the beginning of the content
        assert!(result.output.starts_with("1| AAAA"));
        // Should contain truncation notice since content exceeds MAX_CHARS
        assert!(result.output.contains("chars truncated"));
        // Should contain end-of-file notice (1 line total)
        assert!(result.output.contains("End of file — 1 lines total"));
        // Should NOT be empty content — the fix ensures the prefix is preserved
        assert!(result.output.len() > 100);
    }
}