package config

import (
	"fmt"
	"io"
	"os"
	"path/filepath"
	"regexp"
	"sort"
	"strings"

	"gopkg.in/yaml.v3"
)

// LoadPipeline loads pipeline configuration from a YAML file with strict field checking.
func LoadPipeline(path string) (*PipelineConfig, error) {
	var cfg PipelineConfig
	if err := decodeStrictYAML("pipeline", path, &cfg); err != nil {
		return nil, fmt.Errorf("load pipeline config: %w", err)
	}
	applyPipelineDefaults(&cfg)
	return &cfg, nil
}

// LoadCampaign loads campaign configuration from a YAML file with strict field checking.
func LoadCampaign(path string) (*CampaignConfig, error) {
	var cfg CampaignConfig
	if err := decodeStrictYAML("campaign", path, &cfg); err != nil {
		return nil, fmt.Errorf("load campaign config: %w", err)
	}
	return &cfg, nil
}

// LoadSession loads session configuration from a YAML file with strict field checking.
func LoadSession(path string) (*SessionConfig, error) {
	return LoadSessionWithOptions(path, SessionLoadOptions{})
}

// SessionLoadOptions configures expected session identity checks.
type SessionLoadOptions struct {
	SessionID         string
	PreviousSessionID string
}

// LoadSessionWithOptions loads session configuration from a YAML file with
// strict field checking.
func LoadSessionWithOptions(path string, opts SessionLoadOptions) (*SessionConfig, error) {
	sessionBytes, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("load session config: session file %q: open: %w", path, err)
	}
	return LoadSessionBytesWithOptions(path, sessionBytes, opts)
}

// LoadSessionBytesWithOptions loads session configuration from YAML bytes with
// strict field checking.
func LoadSessionBytesWithOptions(label string, data []byte, opts SessionLoadOptions) (*SessionConfig, error) {
	if err := rejectSessionTemplatePlaceholders(label, string(data)); err != nil {
		return nil, fmt.Errorf("load session config: %w", err)
	}

	var cfg SessionConfig
	if err := decodeStrictYAMLFromReader("session", label, strings.NewReader(string(data)), &cfg); err != nil {
		return nil, fmt.Errorf("load session config: %w", err)
	}
	if strings.TrimSpace(opts.SessionID) != "" && strings.TrimSpace(cfg.SessionID) != "" && strings.TrimSpace(cfg.SessionID) != strings.TrimSpace(opts.SessionID) {
		return nil, fmt.Errorf(
			"load session config: session file %q: session_id mismatch: --session-id %q does not match session_id %q",
			label,
			strings.TrimSpace(opts.SessionID),
			strings.TrimSpace(cfg.SessionID),
		)
	}
	if strings.TrimSpace(opts.PreviousSessionID) != "" &&
		strings.TrimSpace(cfg.PreviousSessionID) != "" &&
		strings.TrimSpace(cfg.PreviousSessionID) != strings.TrimSpace(opts.PreviousSessionID) {
		return nil, fmt.Errorf(
			"load session config: session file %q: previous_session_id mismatch: --previous-session-id %q does not match previous_session_id %q",
			label,
			strings.TrimSpace(opts.PreviousSessionID),
			strings.TrimSpace(cfg.PreviousSessionID),
		)
	}
	return &cfg, nil
}

// LoadArchiveLockStoreBytes loads a mutable session lock store with strict
// field checking and source validation.
func LoadArchiveLockStoreBytes(label string, data []byte, scriptorium *ScriptoriumConfig) (*ArchiveLockStore, error) {
	var store ArchiveLockStore
	if err := decodeStrictYAMLFromReader("archive lock store", label, strings.NewReader(string(data)), &store); err != nil {
		return nil, fmt.Errorf("load archive lock store: %w", err)
	}
	locks, err := ValidateArchiveLockRules(store.Locks, scriptorium, "locks")
	if err != nil {
		return nil, fmt.Errorf("load archive lock store: %w", err)
	}
	store.Locks = locks
	return &store, nil
}

// MarshalArchiveLockStore serializes a mutable lock store as strict-compatible YAML.
func MarshalArchiveLockStore(store *ArchiveLockStore) ([]byte, error) {
	if store == nil {
		store = &ArchiveLockStore{}
	}
	data, err := yaml.Marshal(store)
	if err != nil {
		return nil, fmt.Errorf("marshal archive lock store: %w", err)
	}
	return data, nil
}

// Load loads and resolves combined pipeline, campaign, and session configuration.
// Passing only a session path is supported for package-internal compatibility;
// in that form campaign.yml is expected next to the session file.
func Load(pipelinePath string, paths ...string) (*Config, error) {
	campaignPath, sessionPath, err := campaignSessionPaths(paths...)
	if err != nil {
		return nil, err
	}
	return LoadWithSessionOptions(pipelinePath, campaignPath, sessionPath, SessionLoadOptions{})
}

// LoadWithSessionOptions loads and resolves combined pipeline, campaign, and
// session configuration with expected session identity checks.
func LoadWithSessionOptions(pipelinePath, campaignPath, sessionPath string, sessionOpts SessionLoadOptions) (*Config, error) {
	pipelineCfg, err := LoadPipeline(pipelinePath)
	if err != nil {
		return nil, err
	}

	campaignCfg, err := LoadCampaign(campaignPath)
	if err != nil {
		return nil, err
	}

	sessionCfg, err := LoadSessionWithOptions(sessionPath, sessionOpts)
	if err != nil {
		return nil, err
	}

	return Resolve(pipelinePath, pipelineCfg, campaignPath, campaignCfg, sessionPath, sessionCfg, SessionSource{
		Source:    "session_config",
		LocalPath: sessionPath,
	})
}

// Resolve builds final stage-facing configuration from already loaded
// pipeline, campaign, and session documents.
func Resolve(pipelinePath string, pipelineCfg *PipelineConfig, campaignPath string, campaignCfg *CampaignConfig, sessionPath string, sessionCfg *SessionConfig, sessionSource SessionSource) (*Config, error) {
	stableInputs, err := mergeCampaignSession(campaignCfg, sessionCfg, campaignPath, sessionPath)
	if err != nil {
		return nil, err
	}
	if strings.TrimSpace(sessionSource.Source) == "" {
		sessionSource.Source = "session_config"
	}
	if strings.TrimSpace(sessionSource.LocalPath) == "" {
		sessionSource.LocalPath = sessionPath
	}

	return &Config{
		Pipeline:      pipelineCfg,
		Campaign:      campaignCfg,
		Session:       sessionCfg,
		PipelinePath:  pipelinePath,
		CampaignPath:  campaignPath,
		SessionPath:   sessionPath,
		StableInputs:  stableInputs,
		SessionSource: sessionSource,
	}, nil
}

func campaignSessionPaths(paths ...string) (campaignPath, sessionPath string, err error) {
	switch len(paths) {
	case 1:
		sessionPath = paths[0]
		campaignPath = filepath.Join(filepath.Dir(sessionPath), "campaign.yml")
	case 2:
		campaignPath = paths[0]
		sessionPath = paths[1]
	default:
		return "", "", fmt.Errorf("load config: expected session path or campaign and session paths")
	}
	return campaignPath, sessionPath, nil
}

func mergeCampaignSession(campaignCfg *CampaignConfig, sessionCfg *SessionConfig, campaignPath, sessionPath string) (ResolvedStableInputs, error) {
	if campaignCfg == nil {
		return ResolvedStableInputs{}, fmt.Errorf("campaign config is required")
	}
	if sessionCfg == nil {
		return ResolvedStableInputs{}, fmt.Errorf("session config is required")
	}

	campaignName := strings.TrimSpace(campaignCfg.Campaign)
	sessionCampaign := strings.TrimSpace(sessionCfg.Campaign)
	if sessionCampaign != "" && campaignName != "" && sessionCampaign != campaignName {
		return ResolvedStableInputs{}, fmt.Errorf(
			"campaign/session config invalid: session campaign %q does not match campaign config %q",
			sessionCampaign,
			campaignName,
		)
	}
	if sessionCampaign == "" {
		sessionCfg.Campaign = campaignName
	}

	stable := ResolvedStableInputs{
		SpeakersFile: selectStableInput(
			campaignCfg.Inputs.SpeakersFile,
			sessionCfg.Inputs.SpeakersFile,
			campaignPath,
			sessionPath,
		),
		AutocorrectFile: selectStableInput(
			campaignCfg.Inputs.AutocorrectFile,
			sessionCfg.Inputs.AutocorrectFile,
			campaignPath,
			sessionPath,
		),
		GlossaryFile: selectStableInput(
			campaignCfg.Inputs.GlossaryFile,
			sessionCfg.Inputs.GlossaryFile,
			campaignPath,
			sessionPath,
		),
	}

	sessionCfg.Inputs.SpeakersFile = stable.SpeakersFile.Path
	sessionCfg.Inputs.AutocorrectFile = stable.AutocorrectFile.Path
	sessionCfg.Inputs.GlossaryFile = stable.GlossaryFile.Path
	return stable, nil
}

func selectStableInput(campaignValue, sessionValue, campaignPath, sessionPath string) ResolvedInputFile {
	if strings.TrimSpace(sessionValue) != "" {
		return ResolvedInputFile{
			Path:       sessionValue,
			ConfigPath: sessionPath,
			Source:     "session_config",
		}
	}
	return ResolvedInputFile{
		Path:       campaignValue,
		ConfigPath: campaignPath,
		Source:     "campaign_config",
	}
}

func decodeStrictYAML(kind, path string, out any) error {
	f, err := os.Open(path)
	if err != nil {
		return fmt.Errorf("%s file %q: open: %w", kind, path, err)
	}
	defer f.Close()

	return decodeStrictYAMLFromReader(kind, path, f, out)
}

func decodeStrictYAMLFromReader(kind, path string, r io.Reader, out any) error {
	dec := yaml.NewDecoder(r)
	dec.KnownFields(true)
	if err := dec.Decode(out); err != nil {
		return fmt.Errorf("%s file %q: strict decode failed: %w", kind, path, err)
	}

	var extra any
	if err := dec.Decode(&extra); err != nil && err != io.EOF {
		return fmt.Errorf("%s file %q: trailing content decode failed: %w", kind, path, err)
	}

	return nil
}

var sessionTemplatePlaceholderPattern = regexp.MustCompile(`\{\{[^}]*\}\}`)
var sessionTemplateVariablePattern = regexp.MustCompile(`\{\{\s*([a-zA-Z_][a-zA-Z0-9_]*)\s*\}\}`)

func rejectSessionTemplatePlaceholders(label, content string) error {
	placeholders := sessionTemplatePlaceholderPattern.FindAllString(content, -1)
	if len(placeholders) == 0 {
		return nil
	}
	seen := map[string]struct{}{}
	vars := make([]string, 0, len(placeholders))
	for _, placeholder := range placeholders {
		name := strings.TrimSpace(placeholder)
		if match := sessionTemplateVariablePattern.FindStringSubmatch(placeholder); len(match) > 1 {
			name = match[1]
		}
		if _, ok := seen[name]; ok {
			continue
		}
		seen[name] = struct{}{}
		vars = append(vars, name)
	}
	sort.Strings(vars)
	return fmt.Errorf(
		"session file %q contains template placeholder(s): %s; session.yml must be concrete; run narratio session init to generate it",
		label,
		strings.Join(vars, ", "),
	)
}

func shortName(path, fallback string) string {
	base := filepath.Base(path)
	if base == "." || base == string(filepath.Separator) {
		return fallback
	}
	return base
}

func applyPipelineDefaults(cfg *PipelineConfig) {
	if cfg == nil {
		return
	}
	applyWorkspaceDefaults(&cfg.Workspace)
	applyStorageDefaults(&cfg.Storage)
	applySpoolDefaults(&cfg.Spool)
	applyCacheDefaults(&cfg.Cache)
	applyArchiveDefaults(&cfg.Archive)
	applyWhisperXDefaults(&cfg.WhisperX)
	applySeriatimDefaults(&cfg.Seriatim)
	applyAuditaDefaults(&cfg.Audita)
	if cfg.Normalize == nil {
		cfg.Normalize = &NormalizeConfig{}
	}
	applyNormalizeDefaults(cfg.Normalize)
	applyTrimDefaults(cfg.Trim)
	applyScriptoriumDefaults(cfg.Scriptorium)
}

func applyWorkspaceDefaults(cfg *WorkspaceConfig) {
	if cfg == nil {
		return
	}
	if cfg.Root == "" {
		cfg.Root = DefaultWorkspaceRoot
	}
}

func applyStorageDefaults(cfg *StorageConfig) {
	if cfg == nil {
		return
	}
	if cfg.S3 == nil {
		cfg.S3 = &StorageS3Config{}
	}
	if cfg.S3.RootPrefix == "" {
		cfg.S3.RootPrefix = DefaultStorageS3RootPrefix
	}
	if cfg.S3.AccessKeyIDEnv == "" {
		cfg.S3.AccessKeyIDEnv = DefaultS3AccessKeyIDEnv
	}
	if cfg.S3.SecretKeyEnv == "" {
		cfg.S3.SecretKeyEnv = DefaultS3SecretAccessKeyEnv
	}
}

func applySpoolDefaults(cfg *SpoolConfig) {
	if cfg == nil {
		return
	}
	if cfg.Root == "" {
		cfg.Root = DefaultSpoolRoot
	}
}

func applyCacheDefaults(cfg *CacheConfig) {
	if cfg == nil {
		return
	}
	if cfg.Root == "" {
		cfg.Root = DefaultCacheRoot
	}
	if cfg.S3Audio == nil {
		cfg.S3Audio = boolPtr(DefaultCacheS3Audio)
	}
}

func applyArchiveDefaults(cfg **ArchiveConfig) {
	if cfg == nil {
		return
	}
	if *cfg == nil {
		*cfg = &ArchiveConfig{}
	}

	if (*cfg).Enabled == nil {
		(*cfg).Enabled = boolPtr(DefaultArchiveEnabled)
	}
	if (*cfg).UploadRun == nil {
		(*cfg).UploadRun = boolPtr(DefaultArchiveUploadRun)
	}
	if len((*cfg).PromoteArtifacts) == 0 {
		(*cfg).PromoteArtifacts = append([]ArchivePromotionRule(nil), DefaultArchivePromoteArtifacts...)
	}
	for i := range (*cfg).PromoteArtifacts {
		if (*cfg).PromoteArtifacts[i].Required == nil {
			(*cfg).PromoteArtifacts[i].Required = boolPtr(true)
		}
	}
}

func applyWhisperXDefaults(cfg *WhisperXConfig) {
	if cfg == nil {
		return
	}
	if cfg.Language == "" {
		cfg.Language = DefaultWhisperXLanguage
	}
	if cfg.Timeout == "" {
		cfg.Timeout = DefaultWhisperXTimeout
	}
	if cfg.RetryDelay == "" {
		cfg.RetryDelay = DefaultWhisperXRetryDelay
	}
	if cfg.Concurrency == nil {
		cfg.Concurrency = intPtr(DefaultWhisperXConcurrency)
	}
	if cfg.Retries == nil {
		cfg.Retries = intPtr(DefaultWhisperXRetries)
	}
}

func intPtr(v int) *int {
	p := v
	return &p
}

func applySeriatimDefaults(cfg *SeriatimConfig) {
	if cfg == nil {
		return
	}
	if cfg.Binary == "" {
		cfg.Binary = DefaultSeriatimBinary
	}
	if cfg.Timeout == "" {
		cfg.Timeout = DefaultSeriatimTimeout
	}
	if cfg.OutputSchema == "" {
		cfg.OutputSchema = DefaultSeriatimOutputSchema
	}
	if cfg.CoalesceGap == nil {
		cfg.CoalesceGap = float64Ptr(DefaultSeriatimCoalesceGap)
	}
	if cfg.Report == nil {
		cfg.Report = boolPtr(DefaultSeriatimReport)
	}
}

func applyAuditaDefaults(cfg *AuditaConfig) {
	if cfg == nil {
		return
	}
	if cfg.Binary == "" {
		cfg.Binary = DefaultAuditaBinary
	}
	if cfg.Timeout == "" {
		cfg.Timeout = DefaultAuditaTimeout
	}
	if cfg.Report == nil {
		cfg.Report = boolPtr(DefaultAuditaReport)
	}
}

func applyScriptoriumDefaults(cfg *ScriptoriumConfig) {
	if cfg == nil {
		return
	}
	if cfg.Binary == "" {
		cfg.Binary = DefaultScriptoriumBinary
	}
	if cfg.Timeout == "" {
		cfg.Timeout = DefaultScriptoriumTimeout
	}
}

func applyTrimDefaults(cfg *TrimConfig) {
	if cfg == nil {
		return
	}
	if cfg.Bounds.Timeout == "" {
		cfg.Bounds.Timeout = DefaultTrimBoundsTimeout
	}
	if cfg.Seriatim.Report == nil {
		cfg.Seriatim.Report = boolPtr(DefaultTrimSeriatimReport)
	}
}

func applyNormalizeDefaults(cfg *NormalizeConfig) {
	if cfg == nil {
		return
	}
	if cfg.OutputSchema == "" {
		cfg.OutputSchema = DefaultNormalizeOutputSchema
	}
	if cfg.OutputPath == "" && !cfg.outputPathWasSet() {
		cfg.OutputPath = DefaultNormalizeOutputPath
	}
	if cfg.Report == nil {
		cfg.Report = boolPtr(DefaultNormalizeReport)
	}
}

func float64Ptr(v float64) *float64 {
	p := v
	return &p
}

func boolPtr(v bool) *bool {
	p := v
	return &p
}