package api

import (
	"context"
	"encoding/json"
	"errors"
	"net/http"

	"github.com/gin-gonic/gin"

	"gitea.stevedudenhoeffer.com/steve/pansy/internal/domain"
	"gitea.stevedudenhoeffer.com/steve/pansy/internal/service"
)

// Instance settings (#79): admin-only, instance-wide. The authoritative admin
// check is in the service; requireAdmin here is a cheap early 403 that also
// keeps the route group readable.

// requireAdmin rejects a non-admin actor. It runs after requireAuth, so the
// actor is already resolved and carries IsAdmin — no extra query. Returns 403
// (not 404): a logged-in user knows settings exist, they just may not touch them.
func (h *handlers) requireAdmin() gin.HandlerFunc {
	return func(c *gin.Context) {
		if !mustActor(c).IsAdmin {
			writeAPIError(c, http.StatusForbidden, "FORBIDDEN", "admin access required")
			c.Abort()
			return
		}
		c.Next()
	}
}

// settingsResponse is what GET/PATCH /settings return. It carries the stored
// settings plus a read-only view of what's resolved and live, so the UI can show
// "inheriting ollama-cloud/glm-5.2:cloud from the environment" and whether a key
// is present — without ever exposing the key itself.
type settingsResponse struct {
	Settings *domain.InstanceSettings `json:"settings"`
	// Effective is the configuration actually in force after layering settings
	// over the environment.
	Effective effectiveView `json:"effective"`
}

type effectiveView struct {
	Model   string `json:"model"`
	Enabled bool   `json:"enabled"`
	// HasApiKey reports whether OLLAMA_CLOUD_API_KEY is set. The key itself is
	// never serialized — an admin may know one exists, not what it is.
	HasApiKey bool `json:"hasApiKey"`
	// AgentLive is whether the assistant Runner is actually built right now. It
	// can be false even when Enabled+HasApiKey are true (an unresolvable model),
	// which is exactly the case the UI needs to surface.
	AgentLive bool `json:"agentLive"`
	// VisionModel is the resolved seed-packet model (DB-over-env). VisionReady is
	// whether capture can actually be offered (a key and a model).
	VisionModel string `json:"visionModel"`
	VisionReady bool   `json:"visionReady"`
}

// settingsPayload builds the response, or an error. It does NOT swallow an
// EffectiveAgent failure into a misleading empty "effective" view — an empty
// view would report no model and no key, which reads as "nothing configured"
// rather than "we couldn't read it". Since EffectiveAgent re-reads the same row
// GetInstanceSettings just returned, a failure here is a genuine DB fault worth
// surfacing as a 500, not papering over.
func (h *handlers) settingsPayload(c *gin.Context, st *domain.InstanceSettings) (settingsResponse, error) {
	eff, err := h.svc.EffectiveAgent(c.Request.Context())
	if err != nil {
		return settingsResponse{}, err
	}
	vis, err := h.svc.EffectiveVision(c.Request.Context())
	if err != nil {
		return settingsResponse{}, err
	}
	return settingsResponse{
		Settings: st,
		Effective: effectiveView{
			Model:       eff.Model,
			Enabled:     eff.Enabled,
			HasApiKey:   eff.APIKey != "",
			AgentLive:   h.agent.get() != nil,
			VisionModel: vis.Model,
			VisionReady: vis.Ready(),
		},
	}, nil
}

func (h *handlers) getSettings(c *gin.Context) {
	st, err := h.svc.GetInstanceSettings(c.Request.Context(), mustActor(c).ID)
	if err != nil {
		writeServiceError(c, err)
		return
	}
	payload, err := h.settingsPayload(c, st)
	if err != nil {
		writeServiceError(c, err)
		return
	}
	c.JSON(http.StatusOK, payload)
}

// settingsUpdateRequest is the PATCH body. agentModel "" means inherit the env
// var. agentEnabled is json.RawMessage so an explicit null (inherit) is
// distinguishable from an absent field and from true/false.
type settingsUpdateRequest struct {
	AgentModel   string          `json:"agentModel"`
	AgentEnabled json.RawMessage `json:"agentEnabled"`
	VisionModel  string          `json:"visionModel"`
	Version      int64           `json:"version" binding:"required"`
}

func (h *handlers) updateSettings(c *gin.Context) {
	var req settingsUpdateRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		writeAPIError(c, http.StatusBadRequest, "INVALID_INPUT", "a current version is required")
		return
	}

	// agentEnabled: absent or null → inherit (nil); true/false → explicit override.
	// The shared parseNullable does exactly this three-way decode; present is
	// irrelevant here because absent and null both mean "inherit".
	enabled, _, err := parseNullable[bool](req.AgentEnabled)
	if err != nil {
		writeAPIError(c, http.StatusBadRequest, "INVALID_INPUT", "agentEnabled must be true, false, or null")
		return
	}

	st, err := h.svc.UpdateInstanceSettings(c.Request.Context(), mustActor(c).ID, service.InstanceSettingsPatch{
		AgentModel:   req.AgentModel,
		AgentEnabled: enabled,
		VisionModel:  req.VisionModel,
		Version:      req.Version,
	})
	if err != nil {
		if errors.Is(err, domain.ErrVersionConflict) {
			writeVersionConflict(c, st)
			return
		}
		writeServiceError(c, err)
		return
	}

	// Apply the change to the LIVE assistant. Detached from the request context:
	// the write is committed and the rebuild describes it, so a client that hangs
	// up now must not leave the running Runner out of step with the stored
	// settings. Mirrors the same reasoning as the history-write detachment.
	h.agent.rebuild(context.WithoutCancel(c.Request.Context()))

	payload, err := h.settingsPayload(c, st)
	if err != nil {
		writeServiceError(c, err)
		return
	}
	c.JSON(http.StatusOK, payload)
}