// Package config loads ENKLY_* configuration from a ".env" file into the
// process environment, so `os.Getenv` calls throughout the app (see
// getenv() in cmd/server/main.go) pick up values from ".env" the same
// way they'd pick up real environment variables — without adding a
// third-party dependency like godotenv (this module intentionally keeps
// go.mod to lib/pq + gomarkdown; see the comment on that file).
package envkit

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

// LoadDotEnv reads simple KEY=VALUE lines from path and calls
// os.Setenv for each one whose key isn't already set in the real
// environment — actual environment variables always win, so
// `ENKLY_SMTP_PASSWORD=x make run` still overrides whatever ".env"
// says. Missing files are not an error: ".env" is optional (e.g. in
// docker-compose.yml, config comes from `environment:` instead).
//
// Supported syntax, deliberately small:
//
//	KEY=value
//	KEY="value with spaces, or a # that isn't a comment"
//	KEY='value'
//	# full-line comments and blank lines are ignored
//	export KEY=value   (a leading "export " is stripped, for .env files
//	                     written to be `source`-able in a shell too)
//
// No variable interpolation, no multi-line values.
func LoadDotEnv(path string) error {
	f, err := os.Open(path)
	if err != nil {
		if os.IsNotExist(err) {
			return nil
		}
		return fmt.Errorf("config: open %s: %w", path, err)
	}
	defer f.Close()

	scanner := bufio.NewScanner(f)
	lineNo := 0
	for scanner.Scan() {
		lineNo++
		line := strings.TrimSpace(scanner.Text())
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}
		line = strings.TrimPrefix(line, "export ")

		key, value, ok := strings.Cut(line, "=")
		if !ok {
			return fmt.Errorf("config: %s:%d: expected KEY=VALUE, got %q", path, lineNo, line)
		}
		key = strings.TrimSpace(key)
		value = strings.TrimSpace(value)
		if key == "" {
			return fmt.Errorf("config: %s:%d: empty key", path, lineNo)
		}

		// Strip a single matching pair of surrounding quotes, if present.
		if len(value) >= 2 {
			first, last := value[0], value[len(value)-1]
			if (first == '"' && last == '"') || (first == '\'' && last == '\'') {
				value = value[1 : len(value)-1]
			}
		}

		if _, alreadySet := os.LookupEnv(key); alreadySet {
			continue // real environment variables take precedence
		}
		if err := os.Setenv(key, value); err != nil {
			return fmt.Errorf("config: set %s: %w", key, err)
		}
	}
	return scanner.Err()
}