package infra

import (
	"bufio"
	"fmt"
	"os"
	"strings"
)

// DotenvLoad parses a .env file and sets environment variables via os.Setenv.
// It does NOT overwrite variables that are already set in the environment.
//
// Parsing rules:
//   - Lines starting with # (after trimming) are ignored as comments.
//   - Blank lines are ignored.
//   - Lines must follow the KEY=VALUE format.
//   - Values may be optionally quoted with single or double quotes; quotes are stripped.
//   - Inline comments (# after value) are NOT stripped — the raw value after = is used.
//
// Returns an error if the file cannot be opened or if a line has no '=' separator.
func DotenvLoad(path string) error {
	f, err := os.Open(path)
	if err != nil {
		return fmt.Errorf("dotenv_load: open %q: %w", path, err)
	}
	defer f.Close()

	scanner := bufio.NewScanner(f)
	lineNum := 0
	for scanner.Scan() {
		lineNum++
		line := strings.TrimSpace(scanner.Text())

		// skip blank lines and comments
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}

		idx := strings.IndexByte(line, '=')
		if idx < 0 {
			return fmt.Errorf("dotenv_load: %q line %d: missing '=' in %q", path, lineNum, line)
		}

		key := strings.TrimSpace(line[:idx])
		val := line[idx+1:]

		// strip surrounding quotes from value
		val = stripQuotes(val)

		// only set if not already present
		if os.Getenv(key) == "" {
			if err := os.Setenv(key, val); err != nil {
				return fmt.Errorf("dotenv_load: setenv %q: %w", key, err)
			}
		}
	}

	if err := scanner.Err(); err != nil {
		return fmt.Errorf("dotenv_load: scan %q: %w", path, err)
	}
	return nil
}

// stripQuotes removes surrounding single or double quotes from a string.
func stripQuotes(s string) string {
	if len(s) >= 2 {
		if (s[0] == '"' && s[len(s)-1] == '"') ||
			(s[0] == '\'' && s[len(s)-1] == '\'') {
			return s[1 : len(s)-1]
		}
	}
	return s
}