package metadata

import (
	"context"
	"encoding/json"
	"fmt"
	"log/slog"
	"sort"

	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"
)

// ChainEntry represents a single entry in a library's provider chain.
type ChainEntry struct {
	PluginInstallationID int
	CapabilityID         string
	CapabilityType       string // always "metadata_provider.v1" for now
	ContentLevel         string // "movie", "series", "season", "episode", or "" (legacy)
	Priority             int
	Enabled              bool
}

// ChainRepository provides operations for the library_provider_chains table.
type ChainRepository struct {
	pool *pgxpool.Pool
}

// NewChainRepository creates a new ChainRepository.
func NewChainRepository(pool *pgxpool.Pool) *ChainRepository {
	return &ChainRepository{pool: pool}
}

// Pool returns the underlying connection pool.
func (r *ChainRepository) Pool() *pgxpool.Pool {
	return r.pool
}

// SetChain replaces the entire provider chain for a given media folder.
func (r *ChainRepository) SetChain(ctx context.Context, folderID int, entries []ChainEntry) error {
	tx, err := r.pool.BeginTx(ctx, pgx.TxOptions{})
	if err != nil {
		return fmt.Errorf("beginning chain transaction: %w", err)
	}
	defer func() { _ = tx.Rollback(ctx) }()

	_, err = tx.Exec(ctx, "DELETE FROM library_provider_chains WHERE media_folder_id = $1", folderID)
	if err != nil {
		return fmt.Errorf("deleting existing chain: %w", err)
	}

	for _, entry := range entries {
		capType := entry.CapabilityType
		if capType == "" {
			capType = "metadata_provider.v1"
		}
		_, err = tx.Exec(ctx,
			`INSERT INTO library_provider_chains (media_folder_id, plugin_installation_id, capability_id, capability_type, content_level, priority, enabled)
			 VALUES ($1, $2, $3, $4, $5, $6, $7)`,
			folderID, entry.PluginInstallationID, entry.CapabilityID, capType, entry.ContentLevel, entry.Priority, entry.Enabled,
		)
		if err != nil {
			return fmt.Errorf("inserting chain entry (install=%d, cap=%s, level=%s, priority=%d): %w",
				entry.PluginInstallationID, entry.CapabilityID, entry.ContentLevel, entry.Priority, err)
		}
	}

	if err := tx.Commit(ctx); err != nil {
		return fmt.Errorf("committing chain transaction: %w", err)
	}
	return nil
}

// GetChain returns entries for a specific content level. If no per-level entries
// exist, falls back to legacy flat entries (content_level = ”).
func (r *ChainRepository) GetChain(ctx context.Context, folderID int, contentLevel string) ([]ChainEntry, error) {
	rows, err := r.pool.Query(ctx,
		`SELECT plugin_installation_id, capability_id, capability_type, content_level, priority, enabled
		 FROM library_provider_chains
		 WHERE media_folder_id = $1 AND content_level = $2
		 ORDER BY priority ASC`,
		folderID, contentLevel,
	)
	if err != nil {
		return nil, fmt.Errorf("querying chain: %w", err)
	}
	defer rows.Close()

	var entries []ChainEntry
	for rows.Next() {
		var e ChainEntry
		if err := rows.Scan(&e.PluginInstallationID, &e.CapabilityID, &e.CapabilityType, &e.ContentLevel, &e.Priority, &e.Enabled); err != nil {
			return nil, fmt.Errorf("scanning chain entry: %w", err)
		}
		entries = append(entries, e)
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("iterating chain rows: %w", err)
	}

	// Fall back to legacy flat chain if no per-level entries exist.
	if len(entries) == 0 && contentLevel != "" {
		return r.GetChain(ctx, folderID, "")
	}

	if entries == nil {
		entries = []ChainEntry{}
	}
	return entries, nil
}

// GetAllChainEntries returns every chain entry for a folder, across all content levels.
func (r *ChainRepository) GetAllChainEntries(ctx context.Context, folderID int) ([]ChainEntry, error) {
	rows, err := r.pool.Query(ctx,
		`SELECT plugin_installation_id, capability_id, capability_type, content_level, priority, enabled
		 FROM library_provider_chains
		 WHERE media_folder_id = $1
		 ORDER BY content_level, priority ASC`,
		folderID,
	)
	if err != nil {
		return nil, fmt.Errorf("querying all chain entries: %w", err)
	}
	defer rows.Close()

	var entries []ChainEntry
	for rows.Next() {
		var e ChainEntry
		if err := rows.Scan(&e.PluginInstallationID, &e.CapabilityID, &e.CapabilityType, &e.ContentLevel, &e.Priority, &e.Enabled); err != nil {
			return nil, fmt.Errorf("scanning chain entry: %w", err)
		}
		entries = append(entries, e)
	}
	return entries, rows.Err()
}

// DeleteChain removes all provider chain entries for a given media folder.
func (r *ChainRepository) DeleteChain(ctx context.Context, folderID int) error {
	_, err := r.pool.Exec(ctx, "DELETE FROM library_provider_chains WHERE media_folder_id = $1", folderID)
	if err != nil {
		return fmt.Errorf("deleting chain: %w", err)
	}
	return nil
}

// AppendProviderToAllChains adds a provider to every existing library chain
// (per content level) that doesn't already include it. The defaultPriority
// callback returns the plugin's declared priority for a content level (0 means
// the plugin doesn't declare that level — the entry is still added but disabled).
func (r *ChainRepository) AppendProviderToAllChains(
	ctx context.Context,
	pluginInstallationID int,
	capabilityID string,
	defaultPriority func(contentLevel string) int,
) error {
	// Find every distinct (folder, level) pair that has chain entries.
	rows, err := r.pool.Query(ctx,
		`SELECT DISTINCT media_folder_id, content_level
		 FROM library_provider_chains`)
	if err != nil {
		return fmt.Errorf("listing chain groups: %w", err)
	}
	defer rows.Close()

	type chainGroup struct {
		folderID     int
		contentLevel string
	}
	var groups []chainGroup
	for rows.Next() {
		var g chainGroup
		if err := rows.Scan(&g.folderID, &g.contentLevel); err != nil {
			return fmt.Errorf("scanning chain group: %w", err)
		}
		groups = append(groups, g)
	}
	if err := rows.Err(); err != nil {
		return fmt.Errorf("iterating chain groups: %w", err)
	}

	for _, g := range groups {
		// Check if the provider is already in this chain.
		var exists bool
		err := r.pool.QueryRow(ctx,
			`SELECT EXISTS(
				SELECT 1 FROM library_provider_chains
				WHERE media_folder_id = $1 AND content_level = $2
				  AND plugin_installation_id = $3 AND capability_id = $4
			)`, g.folderID, g.contentLevel, pluginInstallationID, capabilityID,
		).Scan(&exists)
		if err != nil {
			return fmt.Errorf("checking chain membership: %w", err)
		}
		if exists {
			continue
		}

		// Determine priority position (append after the last entry).
		var maxPriority int
		err = r.pool.QueryRow(ctx,
			`SELECT COALESCE(MAX(priority), -1)
			 FROM library_provider_chains
			 WHERE media_folder_id = $1 AND content_level = $2`,
			g.folderID, g.contentLevel,
		).Scan(&maxPriority)
		if err != nil {
			return fmt.Errorf("getting max priority: %w", err)
		}

		dp := defaultPriority(g.contentLevel)
		enabled := dp > 0

		_, err = r.pool.Exec(ctx,
			`INSERT INTO library_provider_chains (media_folder_id, plugin_installation_id, capability_id, capability_type, content_level, priority, enabled)
			 VALUES ($1, $2, $3, 'metadata_provider.v1', $4, $5, $6)
			 ON CONFLICT DO NOTHING`,
			g.folderID, pluginInstallationID, capabilityID, g.contentLevel, maxPriority+1, enabled,
		)
		if err != nil {
			return fmt.Errorf("appending provider (install=%d, cap=%s) to folder %d level %q: %w",
				pluginInstallationID, capabilityID, g.folderID, g.contentLevel, err)
		}
	}

	return nil
}

// ResolveChain builds the ordered list of Provider implementations for a given
// media folder and content level. If the folder has custom chain entries, those
// are used. Otherwise all enabled metadata provider capabilities are used,
// ordered by their plugin manifest default_priority for the given content level.
//
// Providers whose underlying plugin installation is disabled are silently skipped.
func ResolveChain(
	ctx context.Context,
	folderID int,
	contentLevel string,
	chainRepo *ChainRepository,
	resolver pluginMetadataResolver,
) ([]Provider, error) {
	chainEntries, err := chainRepo.GetChain(ctx, folderID, contentLevel)
	if err != nil {
		return nil, fmt.Errorf("getting chain for folder %d: %w", folderID, err)
	}

	// Filter to only enabled entries.
	var enabledEntries []ChainEntry
	for _, e := range chainEntries {
		if e.Enabled {
			enabledEntries = append(enabledEntries, e)
		}
	}
	chainEntries = enabledEntries

	if len(chainEntries) > 0 {
		return resolveChainEntries(ctx, chainEntries, resolver, chainRepo.pool), nil
	}

	providers, err := resolveEnabledProvidersByPriority(ctx, contentLevel, resolver, chainRepo.pool)
	if err != nil {
		return nil, err
	}
	return providers, nil
}

// CapabilityInfo holds the fields needed to construct a provider from plugin tables.
type CapabilityInfo struct {
	PluginInstallationID int
	CapabilityID         string
	DisplayName          string
}

// resolveEnabledProviders returns all enabled providers in installation ID order.
// Used by callers that don't have a content-level context (e.g. person refresh).
func resolveEnabledProviders(
	ctx context.Context,
	resolver pluginMetadataResolver,
	pool *pgxpool.Pool,
) ([]Provider, error) {
	caps, err := ListEnabledMetadataCapabilities(ctx, pool)
	if err != nil {
		return nil, err
	}
	return buildProviders(ctx, caps, resolver, pool), nil
}

// resolveEnabledProvidersByPriority returns all enabled providers sorted by
// their plugin manifest default_priority for the given content level. Providers
// without a declared priority are placed last (sorted by installation ID as a tiebreaker).
func resolveEnabledProvidersByPriority(
	ctx context.Context,
	contentLevel string,
	resolver pluginMetadataResolver,
	pool *pgxpool.Pool,
) ([]Provider, error) {
	caps, err := ListEnabledMetadataCapabilities(ctx, pool)
	if err != nil {
		return nil, err
	}

	type ranked struct {
		cap      CapabilityInfo
		priority int
	}

	items := make([]ranked, len(caps))
	for i, c := range caps {
		items[i] = ranked{cap: c, priority: LookupDefaultPriority(ctx, pool, c.PluginInstallationID, contentLevel)}
	}

	sort.SliceStable(items, func(i, j int) bool {
		pi, pj := items[i].priority, items[j].priority
		if (pi == 0) != (pj == 0) {
			return pi != 0
		}
		if pi != pj {
			return pi < pj
		}
		return items[i].cap.PluginInstallationID < items[j].cap.PluginInstallationID
	})

	sorted := make([]CapabilityInfo, len(items))
	for i, item := range items {
		sorted[i] = item.cap
	}
	return buildProviders(ctx, sorted, resolver, pool), nil
}

// LookupDefaultPriority queries plugin_capabilities for a provider's declared
// default_priority at the given content level. Returns 0 if not found.
func LookupDefaultPriority(ctx context.Context, pool *pgxpool.Pool, pluginInstallationID int, contentLevel string) int {
	var metadataJSON []byte
	err := pool.QueryRow(ctx,
		`SELECT metadata FROM plugin_capabilities
		 WHERE plugin_installation_id = $1 AND capability_type = 'metadata_provider.v1'
		 LIMIT 1`,
		pluginInstallationID,
	).Scan(&metadataJSON)
	if err != nil {
		return 0
	}

	return extractDefaultPriority(metadataJSON, contentLevel)
}

// extractDefaultPriority parses the default_priority for a content level from
// capability metadata JSON.
func extractDefaultPriority(metadataJSON []byte, contentLevel string) int {
	var meta map[string]json.RawMessage
	if err := json.Unmarshal(metadataJSON, &meta); err != nil {
		return 0
	}
	// default_priority may be at the top level or nested inside a "metadata" sub-object
	// (plugin capability metadata wraps plugin-declared fields in a "metadata" envelope).
	dpRaw, ok := meta["default_priority"]
	if !ok {
		if innerRaw, innerOK := meta["metadata"]; innerOK {
			var inner map[string]json.RawMessage
			if err := json.Unmarshal(innerRaw, &inner); err == nil {
				dpRaw, ok = inner["default_priority"]
			}
		}
		if !ok {
			return 0
		}
	}
	var dpMap map[string]float64
	if err := json.Unmarshal(dpRaw, &dpMap); err != nil {
		return 0
	}
	if v, ok := dpMap[contentLevel]; ok && v > 0 {
		return int(v)
	}
	return 0
}

// ListEnabledMetadataCapabilities returns all metadata_provider.v1 capabilities
// whose plugin installation is enabled.
func ListEnabledMetadataCapabilities(ctx context.Context, pool *pgxpool.Pool) ([]CapabilityInfo, error) {
	rows, err := pool.Query(ctx,
		`SELECT pc.plugin_installation_id, pc.capability_id,
		        COALESCE(pc.metadata->>'display_name', pc.capability_id)
		 FROM plugin_capabilities pc
		 JOIN plugin_installations pi ON pi.id = pc.plugin_installation_id
		 WHERE pc.capability_type = 'metadata_provider.v1'
		   AND pi.enabled = true
		 ORDER BY pc.plugin_installation_id`)
	if err != nil {
		return nil, fmt.Errorf("listing enabled metadata capabilities: %w", err)
	}
	defer rows.Close()

	var caps []CapabilityInfo
	for rows.Next() {
		var c CapabilityInfo
		if err := rows.Scan(&c.PluginInstallationID, &c.CapabilityID, &c.DisplayName); err != nil {
			return nil, fmt.Errorf("scanning capability: %w", err)
		}
		caps = append(caps, c)
	}
	return caps, rows.Err()
}

// resolveChainEntries builds Provider instances from explicit chain entries,
// skipping providers whose plugin installation is disabled.
func resolveChainEntries(
	ctx context.Context,
	entries []ChainEntry,
	resolver pluginMetadataResolver,
	pool *pgxpool.Pool,
) []Provider {
	caps := make([]CapabilityInfo, 0, len(entries))
	for _, e := range entries {
		displayName := lookupCapabilityDisplayName(ctx, pool, e.PluginInstallationID, e.CapabilityID)
		caps = append(caps, CapabilityInfo{
			PluginInstallationID: e.PluginInstallationID,
			CapabilityID:         e.CapabilityID,
			DisplayName:          displayName,
		})
	}
	return buildProviders(ctx, caps, resolver, pool)
}

// buildProviders constructs Provider instances from capability info, skipping
// providers whose plugin installation is disabled.
func buildProviders(
	ctx context.Context,
	caps []CapabilityInfo,
	resolver pluginMetadataResolver,
	pool *pgxpool.Pool,
) []Provider {
	providers := make([]Provider, 0, len(caps))
	for _, c := range caps {
		var enabled bool
		err := pool.QueryRow(ctx,
			"SELECT enabled FROM plugin_installations WHERE id = $1",
			c.PluginInstallationID,
		).Scan(&enabled)
		if err != nil || !enabled {
			slog.Debug("skipping metadata provider: plugin installation disabled",
				"installation_id", c.PluginInstallationID, "capability_id", c.CapabilityID)
			continue
		}

		provider, err := NewPluginProviderFromCapability(c.PluginInstallationID, c.CapabilityID, c.DisplayName, resolver)
		if err != nil {
			slog.Warn("skipping metadata provider during chain resolution",
				"installation_id", c.PluginInstallationID,
				"capability_id", c.CapabilityID,
				"error", err,
			)
			continue
		}
		providers = append(providers, provider)
	}
	return providers
}

// lookupCapabilityDisplayName retrieves the display name from plugin capability metadata.
func lookupCapabilityDisplayName(ctx context.Context, pool *pgxpool.Pool, installationID int, capabilityID string) string {
	var displayName string
	err := pool.QueryRow(ctx,
		`SELECT COALESCE(metadata->>'display_name', $2)
		 FROM plugin_capabilities
		 WHERE plugin_installation_id = $1 AND capability_id = $2 AND capability_type = 'metadata_provider.v1'`,
		installationID, capabilityID,
	).Scan(&displayName)
	if err != nil {
		return capabilityID
	}
	return displayName
}