package config

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

// DotEnvFile represents a parsed .env file with key-value pairs and comments.
type DotEnvFile struct {
	// Values maps env key (with TF_VAR_ prefix) to its value.
	Values map[string]string
	// Lines preserves original line order for round-tripping.
	Lines []EnvLine
	// Path is the file path this was loaded from.
	Path string
}

// EnvLine represents a single line in a .env file.
type EnvLine struct {
	Key       string // Empty for comment/blank lines
	Value     string // Raw value (without quotes)
	RawLine   string // Original line text
	IsComment bool
}

// ParseDotEnv reads and parses a .env file.
// Handles:
//   - KEY=VALUE assignments
//   - Comments (# prefix)
//   - Quoted values (single and double quotes)
//   - Empty lines
//   - Inline comments after values
func ParseDotEnv(path string) (*DotEnvFile, error) {
	f, err := os.Open(path)
	if err != nil {
		return nil, fmt.Errorf("opening .env file %s: %w", path, err)
	}
	defer f.Close()

	env := &DotEnvFile{
		Values: make(map[string]string),
		Path:   path,
	}

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

		line := EnvLine{RawLine: raw}

		if trimmed == "" || strings.HasPrefix(trimmed, "#") {
			line.IsComment = true
			env.Lines = append(env.Lines, line)
			continue
		}

		// Parse KEY=VALUE
		idx := strings.Index(trimmed, "=")
		if idx < 0 {
			// Not a valid assignment, treat as comment
			line.IsComment = true
			env.Lines = append(env.Lines, line)
			continue
		}

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

		// Strip inline comment (only outside quotes)
		val = stripInlineComment(val)

		// Unquote
		val = unquoteValue(val)

		line.Key = key
		line.Value = val
		env.Values[key] = val
		env.Lines = append(env.Lines, line)
	}

	if err := scanner.Err(); err != nil {
		return nil, fmt.Errorf("reading .env file %s: %w", path, err)
	}

	return env, nil
}

// GetVar returns the value for a TF variable by name.
// It tries both "TF_VAR_<name>" and "<name>" as keys.
func (e *DotEnvFile) GetVar(name string) (string, bool) {
	if v, ok := e.Values["TF_VAR_"+name]; ok {
		return v, true
	}
	if v, ok := e.Values[name]; ok {
		return v, true
	}
	return "", false
}

// SetVar sets a TF variable value (stored with TF_VAR_ prefix).
func (e *DotEnvFile) SetVar(name, value string) {
	key := "TF_VAR_" + name
	e.Values[key] = value

	// Update existing line or add new
	for i, l := range e.Lines {
		if l.Key == key {
			e.Lines[i].Value = value
			return
		}
	}
	e.Lines = append(e.Lines, EnvLine{Key: key, Value: value})
}

// ToConfig converts parsed .env values into a Config struct,
// stripping TF_VAR_ prefixes to get TF variable names.
func (e *DotEnvFile) ToConfig() *Config {
	cfg := &Config{
		Variables: make(map[string]string),
	}
	for k, v := range e.Values {
		name := strings.TrimPrefix(k, "TF_VAR_")
		cfg.Variables[name] = v
	}
	return cfg
}

// stripInlineComment removes inline comments from a value.
// Handles both quoted and unquoted values.
func stripInlineComment(val string) string {
	// If value starts with a quote, find the closing quote first
	if len(val) > 0 && (val[0] == '"' || val[0] == '\'') {
		quote := val[0]
		for i := 1; i < len(val); i++ {
			if val[i] == quote {
				// Everything after closing quote is inline comment
				rest := strings.TrimSpace(val[i+1:])
				if strings.HasPrefix(rest, "#") {
					return val[:i+1]
				}
				return val
			}
		}
		// Unclosed quote — return as-is
		return val
	}

	// Unquoted: find first # preceded by space
	for i := 0; i < len(val); i++ {
		if val[i] == '#' && (i == 0 || val[i-1] == ' ') {
			return strings.TrimSpace(val[:i])
		}
	}
	return val
}

// unquoteValue removes surrounding quotes from a value.
func unquoteValue(val string) string {
	if len(val) >= 2 {
		if (val[0] == '"' && val[len(val)-1] == '"') ||
			(val[0] == '\'' && val[len(val)-1] == '\'') {
			return val[1 : len(val)-1]
		}
	}
	return val
}

// StripTFVarPrefix removes the TF_VAR_ prefix from an environment variable name.
// Returns the name unchanged if it doesn't have the prefix.
func StripTFVarPrefix(name string) string {
	return strings.TrimPrefix(name, "TF_VAR_")
}