package config

import (
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
)

const (
	DefaultInputReader            = "json-files"
	DefaultOutputModules          = "json"
	DefaultOutputSchema           = OutputSchemaSeriatim
	DefaultPreprocessingModules   = "validate-raw,normalize-speakers,trim-text"
	DefaultPostprocessingModules  = "detect-overlaps,resolve-overlaps,backchannel,filler,coalesce,detect-overlaps,autocorrect,assign-ids,validate-output"
	DefaultOverlapWordRunGap      = 0.75
	DefaultWordRunReorderWindow   = 0.4
	DefaultCoalesceGap            = 3.0
	DefaultCoalesceGapValue       = "3.0"
	DefaultBackchannelMaxDuration = 2.0
	DefaultFillerMaxDuration      = 1.25
	OverlapWordRunGapEnv          = "SERIATIM_OVERLAP_WORD_RUN_GAP"
	WordRunReorderWindowEnv       = "SERIATIM_OVERLAP_WORD_RUN_REORDER_WINDOW"
	BackchannelMaxDurationEnv     = "SERIATIM_BACKCHANNEL_MAX_DURATION"
	FillerMaxDurationEnv          = "SERIATIM_FILLER_MAX_DURATION"
	OutputSchemaSeriatim          = "seriatim"
	OutputSchemaMinimal           = "minimal"
)

// MergeOptions captures raw CLI option values before validation.
type MergeOptions struct {
	InputFiles            []string
	OutputFile            string
	ReportFile            string
	SpeakersFile          string
	AutocorrectFile       string
	InputReader           string
	OutputModules         string
	OutputSchema          string
	PreprocessingModules  string
	PostprocessingModules string
	CoalesceGap           string
}

// Config is the validated runtime configuration for a merge invocation.
type Config struct {
	InputFiles             []string
	OutputFile             string
	ReportFile             string
	SpeakersFile           string
	AutocorrectFile        string
	InputReader            string
	OutputModules          []string
	OutputSchema           string
	PreprocessingModules   []string
	PostprocessingModules  []string
	OverlapWordRunGap      float64
	WordRunReorderWindow   float64
	CoalesceGap            float64
	BackchannelMaxDuration float64
	FillerMaxDuration      float64
}

// NewMergeConfig validates raw merge options and returns normalized config.
func NewMergeConfig(opts MergeOptions) (Config, error) {
	cfg := Config{
		InputReader:            strings.TrimSpace(opts.InputReader),
		OutputModules:          nil,
		OutputSchema:           strings.TrimSpace(opts.OutputSchema),
		PreprocessingModules:   nil,
		PostprocessingModules:  nil,
		OverlapWordRunGap:      DefaultOverlapWordRunGap,
		WordRunReorderWindow:   DefaultWordRunReorderWindow,
		CoalesceGap:            DefaultCoalesceGap,
		BackchannelMaxDuration: DefaultBackchannelMaxDuration,
		FillerMaxDuration:      DefaultFillerMaxDuration,
	}

	if cfg.InputReader == "" {
		return Config{}, errors.New("--input-reader is required")
	}
	if cfg.OutputSchema == "" {
		cfg.OutputSchema = DefaultOutputSchema
	}
	if err := validateOutputSchema(cfg.OutputSchema); err != nil {
		return Config{}, err
	}

	var err error
	cfg.OutputModules, err = parseModuleList(opts.OutputModules)
	if err != nil {
		return Config{}, fmt.Errorf("--output-modules: %w", err)
	}
	cfg.PreprocessingModules, err = parseModuleList(opts.PreprocessingModules)
	if err != nil {
		return Config{}, fmt.Errorf("--preprocessing-modules: %w", err)
	}
	cfg.PostprocessingModules, err = parseModuleList(opts.PostprocessingModules)
	if err != nil {
		return Config{}, fmt.Errorf("--postprocessing-modules: %w", err)
	}
	if len(cfg.OutputModules) == 0 {
		return Config{}, errors.New("--output-modules must include at least one module")
	}

	cfg.InputFiles, err = normalizeInputFiles(opts.InputFiles)
	if err != nil {
		return Config{}, err
	}

	cfg.OutputFile, err = normalizeOutputPath(opts.OutputFile, "--output-file")
	if err != nil {
		return Config{}, err
	}

	if opts.ReportFile != "" {
		cfg.ReportFile, err = normalizeOutputPath(opts.ReportFile, "--report-file")
		if err != nil {
			return Config{}, err
		}
	}

	cfg.SpeakersFile = filepath.Clean(strings.TrimSpace(opts.SpeakersFile))
	if opts.SpeakersFile == "" {
		cfg.SpeakersFile = ""
	}
	cfg.AutocorrectFile = filepath.Clean(strings.TrimSpace(opts.AutocorrectFile))
	if opts.AutocorrectFile == "" {
		cfg.AutocorrectFile = ""
	}

	if cfg.SpeakersFile != "" {
		if err := requireFile(cfg.SpeakersFile, "--speakers"); err != nil {
			return Config{}, err
		}
	}

	if cfg.AutocorrectFile != "" {
		if err := requireFile(cfg.AutocorrectFile, "--autocorrect"); err != nil {
			return Config{}, err
		}
	}

	cfg.OverlapWordRunGap, err = parseOverlapWordRunGap()
	if err != nil {
		return Config{}, err
	}
	cfg.WordRunReorderWindow, err = parseWordRunReorderWindow()
	if err != nil {
		return Config{}, err
	}
	cfg.CoalesceGap, err = parseCoalesceGap(opts.CoalesceGap)
	if err != nil {
		return Config{}, err
	}
	cfg.BackchannelMaxDuration, err = parseBackchannelMaxDuration()
	if err != nil {
		return Config{}, err
	}
	cfg.FillerMaxDuration, err = parseFillerMaxDuration()
	if err != nil {
		return Config{}, err
	}

	return cfg, nil
}

func parseModuleList(value string) ([]string, error) {
	value = strings.TrimSpace(value)
	if value == "" {
		return nil, nil
	}

	parts := strings.Split(value, ",")
	names := make([]string, 0, len(parts))
	for _, part := range parts {
		name := strings.TrimSpace(part)
		if name == "" {
			return nil, errors.New("module names cannot be empty")
		}
		names = append(names, name)
	}
	return names, nil
}

func validateOutputSchema(value string) error {
	switch value {
	case OutputSchemaSeriatim, OutputSchemaMinimal:
		return nil
	default:
		return fmt.Errorf("--output-schema must be one of %q or %q", OutputSchemaSeriatim, OutputSchemaMinimal)
	}
}

func normalizeInputFiles(paths []string) ([]string, error) {
	if len(paths) == 0 {
		return nil, errors.New("at least one --input-file is required")
	}

	normalized := make([]string, 0, len(paths))
	seen := make(map[string]struct{}, len(paths))
	for _, path := range paths {
		path = strings.TrimSpace(path)
		if path == "" {
			return nil, errors.New("--input-file cannot be empty")
		}

		clean := filepath.Clean(path)
		if err := requireFile(clean, "--input-file"); err != nil {
			return nil, err
		}
		if _, exists := seen[clean]; exists {
			return nil, fmt.Errorf("duplicate --input-file %q", clean)
		}
		seen[clean] = struct{}{}
		normalized = append(normalized, clean)
	}
	sort.Strings(normalized)
	return normalized, nil
}

func normalizeOutputPath(path string, flag string) (string, error) {
	path = strings.TrimSpace(path)
	if path == "" {
		return "", fmt.Errorf("%s is required", flag)
	}

	clean := filepath.Clean(path)
	parent := filepath.Dir(clean)
	stat, err := os.Stat(parent)
	if err != nil {
		return "", fmt.Errorf("%s parent directory %q: %w", flag, parent, err)
	}
	if !stat.IsDir() {
		return "", fmt.Errorf("%s parent path %q is not a directory", flag, parent)
	}
	return clean, nil
}

func requireFile(path string, flag string) error {
	stat, err := os.Stat(path)
	if err != nil {
		return fmt.Errorf("%s %q: %w", flag, path, err)
	}
	if stat.IsDir() {
		return fmt.Errorf("%s %q is a directory, not a file", flag, path)
	}
	return nil
}

func parseOverlapWordRunGap() (float64, error) {
	return parsePositiveFloatEnv(OverlapWordRunGapEnv, DefaultOverlapWordRunGap)
}

func parseWordRunReorderWindow() (float64, error) {
	return parsePositiveFloatEnv(WordRunReorderWindowEnv, DefaultWordRunReorderWindow)
}

func parseBackchannelMaxDuration() (float64, error) {
	return parsePositiveFloatEnv(BackchannelMaxDurationEnv, DefaultBackchannelMaxDuration)
}

func parseFillerMaxDuration() (float64, error) {
	return parsePositiveFloatEnv(FillerMaxDurationEnv, DefaultFillerMaxDuration)
}

func parseCoalesceGap(value string) (float64, error) {
	value = strings.TrimSpace(value)
	if value == "" {
		return DefaultCoalesceGap, nil
	}

	gap, err := strconv.ParseFloat(value, 64)
	if err != nil {
		return 0, fmt.Errorf("--coalesce-gap must be a non-negative number of seconds: %w", err)
	}
	if gap < 0 {
		return 0, fmt.Errorf("--coalesce-gap must be non-negative")
	}
	return gap, nil
}

func parsePositiveFloatEnv(name string, defaultValue float64) (float64, error) {
	value := strings.TrimSpace(os.Getenv(name))
	if value == "" {
		return defaultValue, nil
	}

	parsed, err := strconv.ParseFloat(value, 64)
	if err != nil {
		return 0, fmt.Errorf("%s must be a positive number of seconds: %w", name, err)
	}
	if parsed <= 0 {
		return 0, fmt.Errorf("%s must be positive", name)
	}
	return parsed, nil
}

func contains(values []string, target string) bool {
	for _, value := range values {
		if value == target {
			return true
		}
	}
	return false
}