#!/usr/bin/env python3
"""
Migrate Gin handlers to Echo handlers
"""
import re
import sys

def migrate_handler_file(content):
    """Migrate a single handler file from Gin to Echo"""

    # 1. Import changes
    content = re.sub(r'"github\.com/gin-gonic/gin"', '"github.com/labstack/echo/v4"', content)

    # Add validator import if not present
    if '"github.com/treytartt/casera-api/internal/validator"' not in content:
        content = re.sub(
            r'("github\.com/treytartt/casera-api/internal/services"\n)',
            r'\1\t"github.com/treytartt/casera-api/internal/validator"\n',
            content
        )

    # 2. Handler signatures - must return error
    content = re.sub(
        r'func \(h \*(\w+Handler)\) (\w+)\(c \*gin\.Context\) {',
        r'func (h *\1) \2(c echo.Context) error {',
        content
    )

    # 3. c.MustGet -> c.Get
    content = re.sub(r'c\.MustGet\(', 'c.Get(', content)

    # 4. Bind and validate separately
    # Match ShouldBindJSON pattern and replace with Bind + Validate
    def replace_bind_validate(match):
        indent = match.group(1)
        var_name = match.group(2)
        error_block = match.group(3)

        # Replace the error block to use 'return'
        error_block_fixed = re.sub(r'\n(\t+)c\.JSON\(', r'\n\1return c.JSON(', error_block)
        error_block_fixed = re.sub(r'\n(\t+)\}\n(\t+)return\n', r'\n\1}\n', error_block_fixed)

        return (f'{indent}if err := c.Bind(&{var_name}); err != nil {{\n{error_block_fixed}'
                f'{indent}}}\n'
                f'{indent}if err := c.Validate(&{var_name}); err != nil {{\n'
                f'{indent}\treturn c.JSON(http.StatusBadRequest, validator.FormatValidationErrors(err))\n'
                f'{indent}}}')

    # Handle ShouldBindJSON with error handling
    content = re.sub(
        r'(\t+)if err := c\.ShouldBindJSON\(&(\w+)\); err != nil \{((?:\n(?:\1\t.*|))*\n\1\}\n\1\treturn\n)',
        replace_bind_validate,
        content
    )

    # Handle optional ShouldBindJSON (no error check)
    content = re.sub(r'c\.ShouldBindJSON\(&(\w+)\)', r'c.Bind(&\1)', content)

    # 5. gin.H -> map[string]interface{}
    content = re.sub(r'gin\.H\{', 'map[string]interface{}{', content)

    # 6. c.Query -> c.QueryParam
    content = re.sub(r'c\.Query\(', 'c.QueryParam(', content)

    # 7. c.PostForm -> c.FormValue
    content = re.sub(r'c\.PostForm\(', 'c.FormValue(', content)

    # 8. c.GetHeader -> c.Request().Header.Get
    content = re.sub(r'c\.GetHeader\(', 'c.Request().Header.Get(', content)

    # 9. c.Request.Context() -> c.Request().Context()
    content = re.sub(r'c\.Request\.Context\(\)', 'c.Request().Context()', content)

    # 10. All c.JSON, c.Status calls must have 'return'
    # Match c.JSON without return
    content = re.sub(
        r'(\n\t+)c\.JSON\(([^)]+\))',
        r'\1return c.JSON(\2',
        content
    )

    # Match c.Status -> c.NoContent
    content = re.sub(
        r'(\n\t+)c\.Status\(([^)]+)\)',
        r'\1return c.NoContent(\2)',
        content
    )

    # 11. Fix double 'return return' issues
    content = re.sub(r'return return c\.', 'return c.', content)

    # 12. Remove standalone 'return' at end of functions (now returns values)
    # This is tricky - we need to remove lines that are just '\treturn\n}' at function end
    content = re.sub(r'\n\treturn\n\}$', r'\n}', content, flags=re.MULTILINE)
    content = re.sub(r'\n(\t+)return\n(\1)\}', r'\n\2}', content)

    return content

if __name__ == '__main__':
    if len(sys.argv) < 2:
        print("Usage: migrate_handlers.py <handler_file.go>")
        sys.exit(1)

    filename = sys.argv[1]

    with open(filename, 'r') as f:
        content = f.read()

    migrated = migrate_handler_file(content)

    with open(filename, 'w') as f:
        f.write(migrated)

    print(f"Migrated {filename}")