package tools

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

	"gitea.stevedudenhoeffer.com/steve/executus/tool"
)

// nowParams is the LLM-facing param struct for current_time / now.
//
// Why optional `timezone`: most agent prompts know the user's local
// timezone (it's in the chatbot's system prompt) but the agent has
// no way to override on a per-call basis. An explicit arg lets a
// research skill ask "what time is it in NYC for the user reading
// this report?" without needing access to a member-config lookup
// tool.
type nowParams struct {
	Timezone string `json:"timezone,omitempty" description:"Optional IANA timezone name (e.g. 'America/Chicago', 'Europe/London'). Defaults to the calling user's configured timezone, falling back to UTC."`
}

// nowResponse is the JSON envelope returned to the agent.
//
// Why a structured shape: the v1 tool returned a markdown blob.
// Agents that needed just the year had to substring-parse, which
// fails on locale variations. JSON lets the agent pick the field
// it cares about.
type nowResponse struct {
	NowISO   string `json:"now_iso"`
	NowHuman string `json:"now_human"`
	Timezone string `json:"timezone"`
	Weekday  string `json:"weekday"`
	Year     int    `json:"year"`
	Month    int    `json:"month"`
	Day      int    `json:"day"`
	Hour     int    `json:"hour"`
	Minute   int    `json:"minute"`
	Second   int    `json:"second"`
	Warning  string `json:"warning,omitempty"`
}

// NewNow constructs the v11 current_time / now tool. The provider
// supplies the calling member's configured timezone (per-user
// localisation). nil falls back to UTC.
//
// V11 keeps the registered tool name "now" for back-compat with the
// existing tool catalog tests AND adds the same tool surface under
// the agent-facing description "current time". The design spec
// called the tool "current_time" but the v1 registry already used
// "now" — switching the registry name would break stored skills'
// `tools` lists. Same name, expanded behaviour.
func NewNow(provider CurrentTimeProvider) tool.Tool {
	return tool.NewGatedTool[nowParams](
		"now",
		"Return the current time. Optional 'timezone' (IANA name e.g. 'America/Chicago'); defaults to the calling user's configured timezone or UTC. Returns ISO + human-readable formats plus structured year/month/day/weekday for time-relative reasoning. Use this BEFORE assuming a year — the agent's knowledge cut-off may differ from real time.",
		tool.Permission{
			AuthoringRequirement: tool.RequirementAnyone,
			OperatesOn:           tool.ScopeGlobal,
			SafeForShare:         true,
			Categories:           []string{"utility"},
		},
		func(ctx context.Context, inv tool.Invocation, p nowParams) (string, error) {
			tzName := strings.TrimSpace(p.Timezone)
			warning := ""
			if tzName == "" && provider != nil {
				tzName = provider.UserTimezone(ctx, inv.CallerID)
			}
			if tzName == "" {
				tzName = "UTC"
			}
			loc, err := time.LoadLocation(tzName)
			if err != nil {
				warning = fmt.Sprintf("unknown timezone %q; falling back to UTC", tzName)
				tzName = "UTC"
				loc = time.UTC
			}
			t := time.Now().In(loc)
			out := nowResponse{
				NowISO:   t.Format(time.RFC3339),
				NowHuman: t.Format("Monday, January 2, 2006 at 3:04 PM MST"),
				Timezone: tzName,
				Weekday:  t.Weekday().String(),
				Year:     t.Year(),
				Month:    int(t.Month()),
				Day:      t.Day(),
				Hour:     t.Hour(),
				Minute:   t.Minute(),
				Second:   t.Second(),
				Warning:  warning,
			}
			b, mErr := json.Marshal(out)
			if mErr != nil {
				return "", fmt.Errorf("now: marshal: %w", mErr)
			}
			return string(b), nil
		},
	)
}