package main

import (
	"context"
	"database/sql"
	"fmt"
	"time"

	_ "github.com/lib/pq"
)

// app is the model of the oodviewer app.
// The data modeled is a K/V map from string ('Term') to list of entries.
type app struct {
	db *sql.DB
}

// term represents a key in the K/V map of the model.
type term struct {
	// Name of the term, the 'K' of the K/V map.
	Name string
	// Count of entries (len(V) of the K/V map).
	Entries uint64
}

// entry is an element contained under a term. A list of entries ([]entry) is
// the 'V' of the K/V map.
type entry struct {
	Entry  string `json:"entry"`
	Added  int64  `json:"added"`
	Author string `json:"author"`
}

// newApp returns an instantiated app given a lib/pq postgres connection
// string.
func newApp(postgres string) (*app, error) {
	db, err := sql.Open("postgres", flagPostgres)
	if err != nil {
		return nil, fmt.Errorf("Open: %v", err)
	}

	return &app{
		db: db,
	}, nil
}

// getTerms returns all terms stored in the database.
func (a *app) getTerms(ctx context.Context) ([]term, error) {
	rows, err := a.db.QueryContext(ctx, `
		SELECT
			_term._name,
			count(_entry._text)
		FROM
			_term
		LEFT JOIN _entry
		ON
			_entry._term_oid = _term._oid
		GROUP BY _term._oid
		ORDER BY _term._name
	`)
	if err != nil {
		return nil, err
	}
	var res []term
	for rows.Next() {
		var name string
		var count uint64
		if err := rows.Scan(&name, &count); err != nil {
			return nil, err
		}
		res = append(res, term{
			Name:    name,
			Entries: count,
		})
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	return res, err
}

// getEntries returns all entries of a given term stored in the database.
func (a *app) getEntries(ctx context.Context, name string) ([]entry, error) {
	rows, err := a.db.QueryContext(ctx, `
		SELECT
			_entry._text,
			_entry._added_at,
			_entry._added_by
		FROM
			_term
		LEFT JOIN _entry
		ON _entry._term_oid = _term._oid
		WHERE lower(_term._name) = lower($1)
		ORDER BY _entry._added_at
	`, name)
	if err != nil {
		return nil, err
	}
	var res []entry
	for rows.Next() {
		var text string
		var added time.Time
		var author string
		if err := rows.Scan(&text, &added, &author); err != nil {
			return nil, err
		}
		res = append(res, entry{
			Entry:  text,
			Added:  added.Unix(),
			Author: author,
		})
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	return res, err
}