package config

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

	"gitea.maximumdirect.net/eric/narratio/internal/fileops"
)

// LoadPipeline loads pipeline configuration from a YAML file with strict field checking.
func LoadPipeline(path string) (*PipelineConfig, error) {
	return LoadPipelineWithOptions(path, PipelineLoadOptions{})
}

// PipelineLoadOptions carries an optional explicit profile selection. Nil,
// empty, and the exact name "default" select the base configuration.
type PipelineLoadOptions struct {
	Profile *string
}

// LoadPipelineWithOptions loads pipeline configuration with strict field
// checking and optional named-profile selection.
func LoadPipelineWithOptions(path string, opts PipelineLoadOptions) (*PipelineConfig, error) {
	cfg, err := loadPipelineWithConfigKit(path, opts)
	if err != nil {
		return nil, err
	}
	return finalizeLoadedPipeline(path, cfg)
}

// LoadPipelineProfilePair resolves two profiles as independent ConfigKit loads.
func LoadPipelineProfilePair(path, leftProfile, rightProfile string) (*PipelineConfig, *PipelineConfig, error) {
	if leftProfile == rightProfile {
		return nil, nil, fmt.Errorf("load pipeline profiles: left and right profile selections must differ")
	}
	leftOptions := PipelineLoadOptions{Profile: &leftProfile}
	rightOptions := PipelineLoadOptions{Profile: &rightProfile}
	left, err := LoadPipelineWithOptions(path, leftOptions)
	if err != nil {
		return nil, nil, fmt.Errorf("load left pipeline profile: %w", err)
	}
	right, err := LoadPipelineWithOptions(path, rightOptions)
	if err != nil {
		return nil, nil, fmt.Errorf("load right pipeline profile: %w", err)
	}
	return left, right, nil
}

func finalizeLoadedPipeline(path string, cfg *PipelineConfig) (*PipelineConfig, error) {
	captureLogicalNotariusPaths(cfg)
	if err := resolveNotariusPaths(cfg, path); err != nil {
		return nil, fmt.Errorf("load pipeline config: %w", err)
	}
	finalizeArtifactDependencies(cfg)
	if err := finalizePipelineResolution(cfg); err != nil {
		return nil, fmt.Errorf("load pipeline config: %w", err)
	}
	retainArtifactFamilyDeclarations(cfg)
	return cfg, nil
}

// LoadCampaign loads campaign configuration from a YAML file with strict field checking.
func LoadCampaign(path string) (*CampaignConfig, error) {
	return loadCampaignWithConfigKit(path)
}

// 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
	Profile           *string
}

// LoadSessionWithOptions loads session configuration from a YAML file with
// strict field checking.
func LoadSessionWithOptions(path string, opts SessionLoadOptions) (*SessionConfig, error) {
	sessionBytes, err := fileops.ReadFileBounded(path, maxConfigDocumentBytes)
	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)
	}

	cfg, err := loadSessionWithConfigKit(label, data)
	if err != nil {
		return nil, 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 expectedPreviousSessionID := strings.TrimSpace(opts.PreviousSessionID); expectedPreviousSessionID != "" {
		actualPreviousSessionID := strings.TrimSpace(cfg.PreviousSessionID)
		if actualPreviousSessionID == "" {
			return nil, fmt.Errorf(
				"load session config: session file %q: previous_session_id is required when --previous-session-id %q is provided",
				label,
				expectedPreviousSessionID,
			)
		}
		if actualPreviousSessionID != expectedPreviousSessionID {
			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,
				expectedPreviousSessionID,
				actualPreviousSessionID,
			)
		}
	}
	return cfg, 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 := LoadPipelineWithOptions(pipelinePath, PipelineLoadOptions{Profile: sessionOpts.Profile})
	if err != nil {
		return nil, err
	}

	campaignCfg, err := LoadCampaign(campaignPath)
	if err != nil {
		return nil, err
	}
	loaded, err := LoadPipelineCampaign(pipelinePath, pipelineCfg, campaignPath, campaignCfg)
	if err != nil {
		return nil, err
	}
	return LoadSessionWithPipelineCampaignOptions(loaded, sessionPath, sessionOpts)
}

// LoadedPipelineCampaign retains one already loaded pipeline and campaign for
// subsequent local or remote session resolution. It prevents a command from
// reloading the root pipeline after campaign selection.
type LoadedPipelineCampaign struct {
	PipelinePath string
	Pipeline     *PipelineConfig
	CampaignPath string
	Campaign     *CampaignConfig
	Party        ResolvedParty
}

// LoadPipelineCampaign combines already loaded pipeline and campaign documents
// with their campaign-owned party source. Callers that later resolve a session
// retain this context rather than independently reimplementing party loading.
func LoadPipelineCampaign(pipelinePath string, pipeline *PipelineConfig, campaignPath string, campaign *CampaignConfig) (LoadedPipelineCampaign, error) {
	if pipeline == nil {
		return LoadedPipelineCampaign{}, fmt.Errorf("pipeline config is required")
	}
	if campaign == nil {
		return LoadedPipelineCampaign{}, fmt.Errorf("campaign config is required")
	}
	party, err := resolveCampaignParty(campaignPath, campaign)
	if err != nil {
		return LoadedPipelineCampaign{}, err
	}
	return LoadPipelineCampaignWithParty(pipelinePath, pipeline, campaignPath, campaign, party)
}

// LoadPipelineCampaignWithParty combines an already loaded pipeline and
// campaign with one already resolved campaign-owned party. It is useful when
// more than one independently resolved pipeline must be expanded against the
// exact same party document.
func LoadPipelineCampaignWithParty(pipelinePath string, pipeline *PipelineConfig, campaignPath string, campaign *CampaignConfig, party ResolvedParty) (LoadedPipelineCampaign, error) {
	if pipeline == nil {
		return LoadedPipelineCampaign{}, fmt.Errorf("pipeline config is required")
	}
	if campaign == nil {
		return LoadedPipelineCampaign{}, fmt.Errorf("campaign config is required")
	}
	if party.Canonical == nil {
		return LoadedPipelineCampaign{}, fmt.Errorf("resolved campaign party is required")
	}
	if err := expandPipelineArtifactFamilies(pipeline, party); err != nil {
		return LoadedPipelineCampaign{}, err
	}
	return LoadedPipelineCampaign{
		PipelinePath: pipelinePath,
		Pipeline:     pipeline,
		CampaignPath: campaignPath,
		Campaign:     campaign,
		Party:        party,
	}, nil
}

// LoadSessionWithPipelineCampaignOptions loads one local session and combines
// it with an already loaded pipeline and campaign.
func LoadSessionWithPipelineCampaignOptions(loaded LoadedPipelineCampaign, sessionPath string, sessionOpts SessionLoadOptions) (*Config, error) {
	sessionCfg, err := LoadSessionWithOptions(sessionPath, sessionOpts)
	if err != nil {
		return nil, err
	}
	return ResolveLoadedPipelineCampaign(loaded, sessionPath, sessionCfg, SessionSource{
		Source:    "session_config",
		LocalPath: sessionPath,
	})
}

// ResolveLoadedPipelineCampaign combines an already loaded pipeline and
// campaign with optional already loaded session data. A nil session preserves
// the resolved pipeline/campaign context for callers that need to locate or
// retrieve a session without rereading the root pipeline.
func ResolveLoadedPipelineCampaign(loaded LoadedPipelineCampaign, sessionPath string, sessionCfg *SessionConfig, sessionSource SessionSource) (*Config, error) {
	if loaded.Pipeline == nil {
		return nil, fmt.Errorf("pipeline config is required")
	}
	if loaded.Campaign == nil {
		return nil, fmt.Errorf("campaign config is required")
	}
	if loaded.Party.Canonical == nil {
		party, err := resolveCampaignParty(loaded.CampaignPath, loaded.Campaign)
		if err != nil {
			return nil, err
		}
		loaded.Party = party
	}
	cfg := &Config{
		Pipeline:      loaded.Pipeline,
		Campaign:      loaded.Campaign,
		Session:       sessionCfg,
		PipelinePath:  loaded.PipelinePath,
		CampaignPath:  loaded.CampaignPath,
		SessionPath:   sessionPath,
		SessionSource: sessionSource,
		Party:         loaded.Party,
	}
	if sessionCfg == nil {
		return cfg, nil
	}

	stableInputs, err := mergeCampaignSession(loaded.Campaign, sessionCfg, loaded.CampaignPath, sessionPath)
	if err != nil {
		return nil, err
	}
	if strings.TrimSpace(cfg.SessionSource.Source) == "" {
		cfg.SessionSource.Source = "session_config"
	}
	if strings.TrimSpace(cfg.SessionSource.LocalPath) == "" {
		cfg.SessionSource.LocalPath = sessionPath
	}
	cfg.StableInputs = stableInputs
	return cfg, nil
}

// 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) {
	if sessionCfg == nil {
		return nil, fmt.Errorf("session config is required")
	}
	loaded, err := LoadPipelineCampaign(pipelinePath, pipelineCfg, campaignPath, campaignCfg)
	if err != nil {
		return nil, err
	}
	return ResolveLoadedPipelineCampaign(loaded, sessionPath, sessionCfg, sessionSource)
}

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")
	}
	if campaignCfg.Inputs.SpellCatalogFile != "" && strings.TrimSpace(campaignCfg.Inputs.SpellCatalogFile) == "" {
		return ResolvedStableInputs{}, fmt.Errorf("campaign.inputs.spell_catalog_file must be non-empty when provided")
	}
	if sessionCfg.Inputs.SpellCatalogFile != "" && strings.TrimSpace(sessionCfg.Inputs.SpellCatalogFile) == "" {
		return ResolvedStableInputs{}, fmt.Errorf("session.inputs.spell_catalog_file must be non-empty when provided")
	}

	campaignName := CampaignID(campaignCfg)
	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,
		),
		PartyFile: selectStableInput(
			campaignCfg.Inputs.PartyFile,
			"",
			campaignPath,
			sessionPath,
		),
		SpellCatalogFile: selectStableInput(
			campaignCfg.Inputs.SpellCatalogFile,
			sessionCfg.Inputs.SpellCatalogFile,
			campaignPath,
			sessionPath,
		),
	}

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

// CampaignID returns the canonical campaign identity from campaign config.
func CampaignID(cfg *CampaignConfig) string {
	if cfg == nil {
		return ""
	}
	return strings.TrimSpace(cfg.CampaignID)
}

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",
	}
}

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 resolveNotariusPaths(cfg *PipelineConfig, pipelinePath string) error {
	if cfg == nil || cfg.Notarius == nil || !cfg.Notarius.Enabled {
		return nil
	}
	pipelineAbs, err := filepath.Abs(pipelinePath)
	if err != nil {
		return fmt.Errorf("resolve pipeline config path %q: %w", pipelinePath, err)
	}
	baseDir := filepath.Dir(pipelineAbs)
	resolve := func(value string) (string, error) {
		trimmed := strings.TrimSpace(value)
		if trimmed == "" {
			return "", nil
		}
		if !filepath.IsAbs(trimmed) {
			trimmed = filepath.Join(baseDir, trimmed)
		}
		return filepath.Abs(trimmed)
	}

	resolvedConfigPath, err := resolve(cfg.Notarius.ConfigPath)
	if err != nil {
		return fmt.Errorf("resolve pipeline.notarius.config_path: %w", err)
	}
	cfg.Notarius.ConfigPath = resolvedConfigPath
	if strings.TrimSpace(cfg.Notarius.WorkingDirectory) == "" {
		if resolvedConfigPath != "" {
			cfg.Notarius.WorkingDirectory = filepath.Dir(resolvedConfigPath)
		}
		return nil
	}
	workingDirectory, err := resolve(cfg.Notarius.WorkingDirectory)
	if err != nil {
		return fmt.Errorf("resolve pipeline.notarius.working_directory: %w", err)
	}
	cfg.Notarius.WorkingDirectory = workingDirectory
	return nil
}