#!/usr/bin/env python3
# description: Replace text in a file; old_string not found is the guard
# Args: <file_path> <old_string> <new_string> [replace_all=true|1|yes]

import sys
import os
import difflib

def format_diff(path, old, new):
    old_lines = old.splitlines(keepends=True)
    new_lines = new.splitlines(keepends=True)
    diff = ''.join(difflib.unified_diff(old_lines, new_lines, fromfile=path, tofile=path))
    if not diff:
        return None
    return f"```diff\n{diff}```"

def find_exact(content, find):
    return find if find in content else None

def find_ws_normalized(content, find):
    nf = ' '.join(find.split())
    find_lines = find.split('\n')
    n = len(find_lines)
    lines = content.split('\n')
    for i in range(len(lines) - n + 1):
        block = '\n'.join(lines[i:i+n])
        if ' '.join(block.split()) == nf:
            return block
    return None

def find_indent_flexible(content, find):
    def deindent(text):
        ls = text.split('\n')
        min_indent = float('inf')
        for l in ls:
            stripped = l.lstrip(' \t')
            if stripped:
                min_indent = min(min_indent, len(l) - len(stripped))
        if min_indent == float('inf'):
            return text
        return '\n'.join(l[min_indent:] if len(l) > min_indent else l.lstrip(' \t') for l in ls)
    nf = deindent(find)
    find_lines = find.split('\n')
    n = len(find_lines)
    lines = content.split('\n')
    for i in range(len(lines) - n + 1):
        block = '\n'.join(lines[i:i+n])
        if deindent(block) == nf:
            return block
    return None

def find_trimmed_boundary(content, find):
    trimmed = find.strip()
    if trimmed == find:
        return None
    if trimmed in content:
        return trimmed
    find_lines = find.split('\n')
    n = len(find_lines)
    lines = content.split('\n')
    for i in range(len(lines) - n + 1):
        block = '\n'.join(lines[i:i+n])
        if block.strip() == trimmed:
            return block
    return None

def robust_replace(content, old_string, new_string, replace_all):
    match = (find_exact(content, old_string) or
             find_ws_normalized(content, old_string) or
             find_indent_flexible(content, old_string) or
             find_trimmed_boundary(content, old_string))
    if match is None:
        return None, "old_string not found in file", False
    if replace_all:
        return content.replace(match, new_string), None, False
    n = content.count(match)
    if n > 1:
        return None, f"old_string is not unique ({n} occurrences); use replace_all=true or provide more context", True
    return content.replace(match, new_string, 1), None, False

if len(sys.argv) < 4:
    print("usage: file_edit <file_path> <old_string> <new_string> [replace_all=true|1|yes]")
    sys.exit(1)

file_path   = sys.argv[1]
old_string  = sys.argv[2]
new_string  = sys.argv[3]
_ra = sys.argv[4].lower() if len(sys.argv) > 4 else ''
replace_all = _ra.split('=')[-1] in ('true', '1', 'yes')

if not os.path.isabs(file_path):
    print(f"STATUS=error STATE_CHANGED=false RETRYABLE=false")
    print(f"error: path must be absolute, got: {file_path}")
    sys.exit(1)
if old_string == new_string:
    print("STATUS=no_change STATE_CHANGED=false RETRYABLE=false")
    print("error: old_string and new_string must be different")
    sys.exit(1)
if not os.path.exists(file_path):
    print(f"STATUS=error STATE_CHANGED=false RETRYABLE=false")
    print(f"error: file not found: {file_path}")
    sys.exit(1)

with open(file_path, 'r', errors='replace') as f:
    original = f.read()

new_content, err, retryable = robust_replace(original, old_string, new_string, replace_all)
if err:
    print(f"STATUS=error STATE_CHANGED=false RETRYABLE={'true' if retryable else 'false'}")
    print(f"error: {err}")
    sys.exit(1)

try:
    with open(file_path, 'w') as f:
        f.write(new_content)
except OSError as e:
    print(f"STATUS=error STATE_CHANGED=false RETRYABLE=false")
    print(f"error: {e}")
    sys.exit(1)

diff = format_diff(file_path, original, new_content)
if diff is None:
    print("STATUS=no_change STATE_CHANGED=false RETRYABLE=false")
    print("(no changes)")
else:
    print("STATUS=done STATE_CHANGED=true")
    print(diff)