package store

import (
	"database/sql"
	"encoding/json"
	"fmt"
	"time"
)

// schema is the durable layout: the lease table, the lease-event log, the
// per-request accounting rows, the host-health poll log, and the daily
// rollup that Prune writes into. Times are Unix milliseconds.
const schema = `
CREATE TABLE IF NOT EXISTS leases (
    route     TEXT NOT NULL,
    fp        TEXT NOT NULL,
    model     TEXT NOT NULL,
    host      TEXT NOT NULL,
    state     TEXT NOT NULL,
    created   INTEGER NOT NULL,
    last_used INTEGER NOT NULL,
    PRIMARY KEY (route, fp, model)
);
CREATE TABLE IF NOT EXISTS lease_events (
    ts        INTEGER NOT NULL,
    route     TEXT NOT NULL,
    model     TEXT NOT NULL,
    from_host TEXT NOT NULL,
    to_host   TEXT NOT NULL,
    reason    TEXT NOT NULL
);
CREATE TABLE IF NOT EXISTS requests (
    id                INTEGER PRIMARY KEY,
    route             TEXT NOT NULL,
    fp                TEXT NOT NULL,
    model             TEXT NOT NULL,
    host              TEXT NOT NULL,
    started           INTEGER NOT NULL,
    queued_ms         INTEGER NOT NULL,
    ttfb_ms           INTEGER NOT NULL,
    total_ms          INTEGER NOT NULL,
    status            INTEGER NOT NULL,
    streamed          INTEGER NOT NULL,
    prompt_tokens     INTEGER NOT NULL,
    cached_tokens     INTEGER NOT NULL,
    completion_tokens INTEGER NOT NULL,
    err               TEXT NOT NULL
);
CREATE TABLE IF NOT EXISTS host_health (
    ts            INTEGER NOT NULL,
    host          TEXT NOT NULL,
    healthy       INTEGER NOT NULL,
    loaded_models TEXT NOT NULL
);
CREATE TABLE IF NOT EXISTS requests_daily (
    day               INTEGER NOT NULL,
    route             TEXT NOT NULL,
    model             TEXT NOT NULL,
    host              TEXT NOT NULL,
    requests          INTEGER NOT NULL,
    errors            INTEGER NOT NULL,
    busy_ms           INTEGER NOT NULL,
    queued_ms         INTEGER NOT NULL,
    prompt_tokens     INTEGER NOT NULL,
    cached_tokens     INTEGER NOT NULL,
    completion_tokens INTEGER NOT NULL,
    PRIMARY KEY (day, route, model, host)
);
`

// byColumn maps a grouping to its table column, rejecting anything else.
func byColumn(b By) (string, error) {
	switch b {
	case ByRoute:
		return "route", nil
	case ByModel:
		return "model", nil
	case ByHost:
		return "host", nil
	default:
		return "", fmt.Errorf("store: unknown grouping %q", b)
	}
}

// midnight returns UTC midnight of the day holding ms.
func midnight(ms int64) int64 {
	return time.UnixMilli(ms).Truncate(24 * time.Hour).UnixMilli()
}

// btoi converts a bool to 0/1 for storage.
func btoi(b bool) int64 {
	if b {
		return 1
	}
	return 0
}

// encodeLoaded serialises a Loaded slice as JSON, writing nil as [].
func encodeLoaded(loaded []string) ([]byte, error) {
	if loaded == nil {
		loaded = []string{}
	}
	return json.Marshal(loaded)
}

// wrap prefixes a driver error with the package name.
func wrap(err error) error {
	if err == nil {
		return nil
	}
	return fmt.Errorf("store: %w", err)
}

func scanLeases(rows *sql.Rows) ([]Lease, error) {
	var out []Lease
	for rows.Next() {
		var (
			l             Lease
			created, last int64
		)
		if err := rows.Scan(&l.Route, &l.FP, &l.Model, &l.Host, (*string)(&l.State), &created, &last); err != nil {
			return nil, wrap(err)
		}
		l.Created = time.UnixMilli(created).UTC()
		l.LastUsed = time.UnixMilli(last).UTC()
		out = append(out, l)
	}
	return out, rows.Err()
}

func scanUsage(rows *sql.Rows) ([]UsageRow, error) {
	var out []UsageRow
	for rows.Next() {
		var u UsageRow
		if err := rows.Scan(&u.Key, &u.Requests, &u.Errors, &u.BusyMs, &u.QueuedMs,
			&u.PromptTokens, &u.CachedTokens, &u.CompletionTokens); err != nil {
			return nil, wrap(err)
		}
		out = append(out, u)
	}
	return out, rows.Err()
}

func scanEvents(rows *sql.Rows) ([]LeaseEvent, error) {
	var out []LeaseEvent
	for rows.Next() {
		var e LeaseEvent
		var ts int64
		if err := rows.Scan(&ts, &e.Route, &e.Model, &e.FromHost, &e.ToHost, (*string)(&e.Reason)); err != nil {
			return nil, wrap(err)
		}
		e.TS = time.UnixMilli(ts).UTC()
		out = append(out, e)
	}
	return out, rows.Err()
}