package main

import (
	"context"
	"encoding/json"
	"fmt"
	"time"

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

const maxToolResultSize = 4096

type store struct {
	pool *pgxpool.Pool
}

func newStore(ctx context.Context, databaseURL string) (*store, error) {
	if databaseURL == "" {
		return nil, nil
	}
	pool, err := pgxpool.New(ctx, databaseURL)
	if err != nil {
		return nil, fmt.Errorf("connect db: %w", err)
	}
	if err := pool.Ping(ctx); err != nil {
		pool.Close()
		return nil, fmt.Errorf("ping db: %w", err)
	}
	return &store{pool: pool}, nil
}

func (s *store) close() {
	if s.pool != nil {
		s.pool.Close()
	}
}

type session struct {
	ID           string    `json:"id"`
	Title        string    `json:"title"`
	Actor        string    `json:"actor"`
	CreatedAt    time.Time `json:"created_at"`
	LastActiveAt time.Time `json:"last_active_at"`
}

type message struct {
	ID        string          `json:"id"`
	SessionID string          `json:"session_id"`
	Role      string          `json:"role"`
	Content   json.RawMessage `json:"content"`
	CreatedAt time.Time       `json:"created_at"`
}

func (s *store) createSession(ctx context.Context, title string) (*session, error) {
	if s == nil {
		return &session{ID: "ephemeral", Title: title, Actor: "agent:nomos"}, nil
	}
	var id string
	err := s.pool.QueryRow(ctx,
		`INSERT INTO agent_sessions (title, actor) VALUES ($1, 'agent:nomos') RETURNING id`,
		title).Scan(&id)
	if err != nil {
		return nil, err
	}
	return &session{ID: id, Title: title, Actor: "agent:nomos", CreatedAt: time.Now(), LastActiveAt: time.Now()}, nil
}

func (s *store) saveMessage(ctx context.Context, sessionID, role string, content json.RawMessage) error {
	if s == nil {
		return nil
	}
	_, err := s.pool.Exec(ctx,
		`INSERT INTO agent_messages (session_id, role, content) VALUES ($1, $2, $3)`,
		sessionID, role, truncateToolResults(content))
	return err
}

func truncateToolResults(content json.RawMessage) json.RawMessage {
	var m map[string]any
	if err := json.Unmarshal(content, &m); err != nil {
		return content
	}
	toolCalls, ok := m["tool_calls"].([]any)
	if !ok || len(toolCalls) == 0 {
		return content
	}
	changed := false
	for i, raw := range toolCalls {
		tc, ok := raw.(map[string]any)
		if !ok {
			continue
		}
		if result, ok := tc["result"]; ok {
			resultJSON, _ := json.Marshal(result)
			if len(resultJSON) > maxToolResultSize {
				tc["result"] = string(resultJSON[:maxToolResultSize]) + fmt.Sprintf("...truncated (%d bytes total)", len(resultJSON))
				toolCalls[i] = tc
				changed = true
			}
		}
	}
	if !changed {
		return content
	}
	m["tool_calls"] = toolCalls
	out, err := json.Marshal(m)
	if err != nil {
		return content
	}
	return out
}

func (s *store) touchSession(ctx context.Context, id string) {
	if s != nil {
		s.pool.Exec(ctx, `UPDATE agent_sessions SET last_active_at=now() WHERE id=$1`, id)
	}
}

func (s *store) listSessions(ctx context.Context) ([]session, error) {
	if s == nil {
		return nil, nil
	}
	rows, err := s.pool.Query(ctx,
		`SELECT id, title, actor, created_at, last_active_at FROM agent_sessions ORDER BY last_active_at DESC LIMIT 50`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var out []session
	for rows.Next() {
		var sess session
		if err := rows.Scan(&sess.ID, &sess.Title, &sess.Actor, &sess.CreatedAt, &sess.LastActiveAt); err != nil {
			return nil, err
		}
		out = append(out, sess)
	}
	return out, rows.Err()
}

func (s *store) getMessages(ctx context.Context, sessionID string) ([]message, error) {
	if s == nil {
		return nil, nil
	}
	rows, err := s.pool.Query(ctx,
		`SELECT id, session_id, role, content, created_at FROM agent_messages WHERE session_id=$1 ORDER BY created_at ASC`,
		sessionID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var out []message
	for rows.Next() {
		var m message
		if err := rows.Scan(&m.ID, &m.SessionID, &m.Role, &m.Content, &m.CreatedAt); err != nil {
			return nil, err
		}
		out = append(out, m)
	}
	return out, rows.Err()
}

func (s *store) deleteSession(ctx context.Context, id string) error {
	if s == nil {
		return nil
	}
	_, err := s.pool.Exec(ctx, `DELETE FROM agent_messages WHERE session_id = $1`, id)
	if err != nil {
		return err
	}
	_, err = s.pool.Exec(ctx, `DELETE FROM agent_sessions WHERE id = $1`, id)
	return err
}

func (s *store) updateSessionTitle(ctx context.Context, id, title string) error {
	if s == nil {
		return nil
	}
	_, err := s.pool.Exec(ctx, `UPDATE agent_sessions SET title = $1 WHERE id = $2`, title, id)
	return err
}

// resolveAgentID looks up the UUID of the agent entity (e.g. "agent:nomos").
// Returns uuid.Nil if the store is absent or the slug is unknown.
func (s *store) resolveAgentID(ctx context.Context, slug string) uuid.UUID {
	if s == nil {
		return uuid.Nil
	}
	var id uuid.UUID
	if err := s.pool.QueryRow(ctx, `SELECT id FROM entities WHERE slug = $1`, slug).Scan(&id); err != nil {
		return uuid.Nil
	}
	return id
}

// logActivity records a tool call. agent_id is the agent entity UUID and is
// NOT NULL in the schema, so we skip logging when it can't be resolved.
// The (nullable) session_id column carries the conversation id.
func (s *store) logActivity(ctx context.Context, agentID uuid.UUID, sessionID, toolName, inputSummary, outputSummary string, durationMs int, success bool, correlationID string) {
	if s == nil || agentID == uuid.Nil {
		return
	}
	s.pool.Exec(ctx, `
		INSERT INTO agent_activity
		    (agent_id, session_id, activity_type, tool_name, input_summary, output_summary,
		     duration_ms, success, correlation_id)
		VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9)`,
		agentID, sessionID, "tool_call", toolName, inputSummary, outputSummary,
		durationMs, success, correlationID)
}