use std::fs;
use std::path::PathBuf;
use serde_json::{json, Value};
use anyhow::{Result, anyhow};
use super::super::Tool;
use super::super::ToolCtx;
use super::super::resolve_path;
use super::helpers::arg_str;

pub struct Edit;

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

    fn description(&self) -> &'static str {
        "Replace a string in a file with a new string. The old string must be unique unless replace_all is true."
    }

    fn parameters(&self) -> Value {
        json!({
            "type": "object",
            "properties": {
                "path": {
                    "type": "string",
                    "description": "Path to the file to edit (relative to workspace root)"
                },
                "old": {
                    "type": "string",
                    "description": "The exact text to replace"
                },
                "new": {
                    "type": "string",
                    "description": "The replacement text"
                },
                "replace_all": {
                    "type": "boolean",
                    "description": "Replace all occurrences instead of requiring uniqueness"
                },
                "reason": {
                    "type": "string",
                    "description": "Reason for the change (must be non-empty)"
                }
            },
            "required": ["path", "old", "new", "reason"]
        })
    }

    fn run(&self, ctx: &ToolCtx, args: &Value) -> Result<String> {
        let rel = arg_str(args, "path")?;
        let old = arg_str(args, "old")?;
        let new_str = arg_str(args, "new")?;
        let reason = arg_str(args, "reason")?;
        if reason.trim().is_empty() {
            anyhow::bail!("reason must be a non-empty string");
        }
        let replace_all = args.get("replace_all").and_then(|v| v.as_bool()).unwrap_or(false);
        let path: PathBuf = resolve_path(&ctx.workspaces, &rel)?;
        if !path.exists() {
            anyhow::bail!("file '{}' does not exist at resolved path {}", rel, path.display());
        }
        if path.is_dir() {
            anyhow::bail!("'{}' is a directory, not a file", rel);
        }
        let content = fs::read_to_string(&path)
            .map_err(|e| anyhow!("failed to read '{}': {}", rel, e))?;
        if !content.contains(&old) {
            anyhow::bail!("old string not found in '{}'", rel);
        }
        if !replace_all {
            let count = content.matches(&old).count();
            if count > 1 {
                anyhow::bail!(
                    "old string appears {} times in '{}'. Set replace_all=true to replace all occurrences, or provide a more specific match.",
                    count, rel
                );
            }
        }
        let new_content = if replace_all {
            content.replace(&old, &new_str)
        } else {
            content.replacen(&old, &new_str, 1)
        };
        fs::write(&path, &new_content)
            .map_err(|e| anyhow!("failed to write '{}': {}", rel, e))?;
        let bytes_diff = if new_content.len() > content.len() {
            new_content.len() - content.len()
        } else {
            content.len() - new_content.len()
        };
        Ok(format!("edited {} ({} byte delta)", rel, bytes_diff as isize))
    }
}