// tools/edit.rs — Search-and-replace file editing
//
// The edit tool performs exact string replacement in files. This is the
// same pattern used by Claude Code and aider — it's more reliable than
// line-number-based editing because the model specifies what it sees,
// not where it thinks it is.
//
// Supports replace_all for bulk renaming (e.g. variable renames).

use anyhow::{Context, Result};
use serde::Deserialize;
use serde_json::json;

use super::ToolDef;

#[derive(Deserialize)]
struct Args {
    file_path: String,
    old_string: String,
    new_string: String,
    #[serde(default)]
    replace_all: bool,
}

pub fn definition() -> ToolDef {
    ToolDef::new(
        "edit_file",
        "Perform exact string replacement in a file. The old_string must appear \
         exactly once in the file (unless replace_all is true). Use read_file first \
         to see the current contents.",
        json!({
            "type": "object",
            "properties": {
                "file_path": {
                    "type": "string",
                    "description": "Absolute path to the file to edit"
                },
                "old_string": {
                    "type": "string",
                    "description": "The exact text to find and replace"
                },
                "new_string": {
                    "type": "string",
                    "description": "The replacement text"
                },
                "replace_all": {
                    "type": "boolean",
                    "description": "Replace all occurrences (default false)"
                }
            },
            "required": ["file_path", "old_string", "new_string"]
        }),
    )
}

pub fn edit_file(args: &serde_json::Value) -> Result<String> {
    let a: Args = serde_json::from_value(args.clone())
        .context("invalid edit_file arguments")?;

    if a.old_string == a.new_string {
        anyhow::bail!("old_string and new_string are identical");
    }

    let content = std::fs::read_to_string(&a.file_path)
        .with_context(|| format!("Failed to read {}", a.file_path))?;

    let count = content.matches(&*a.old_string).count();
    if count == 0 {
        anyhow::bail!("old_string not found in {}", a.file_path);
    }

    if a.replace_all {
        let new_content = content.replace(&*a.old_string, &a.new_string);
        std::fs::write(&a.file_path, &new_content)
            .with_context(|| format!("Failed to write {}", a.file_path))?;
        Ok(format!("Replaced {} occurrences in {}", count, a.file_path))
    } else {
        if count > 1 {
            anyhow::bail!(
                "old_string appears {} times in {} — use replace_all or provide more context \
                 to make it unique",
                count, a.file_path
            );
        }
        let new_content = content.replacen(&*a.old_string, &a.new_string, 1);
        std::fs::write(&a.file_path, &new_content)
            .with_context(|| format!("Failed to write {}", a.file_path))?;
        Ok(format!("Edited {}", a.file_path))
    }
}