package loop

import (
	"context"
	"fmt"
	"sort"
	"strings"

	"ukrrs.com/mopac/harness/internal/config"
	"ukrrs.com/mopac/harness/internal/quota"
	"ukrrs.com/mopac/harness/internal/task"
)

// buildGates constructs the quota gate and resource config for the
// conductor. Quota/resources are opt-in ([quota] enabled / [resources]
// enabled); failures to build (bad schedule, unreachable redis) are fatal
// at startup because a silently missing gate is a silently burning plan.
func buildGates(cfg *config.Config, keys *config.KeyResolver) (*quota.Gate, error) {
	if !cfg.Quota.Enabled && !cfg.Resources.Enabled {
		return nil, nil
	}
	var shared *quota.SharedState
	if cfg.Quota.RedisURL != "" {
		var err error
		shared, err = quota.NewSharedState(cfg.Quota.RedisURL)
		if err != nil {
			return nil, fmt.Errorf("quota redis: %w", err)
		}
	}
	if !cfg.Quota.Enabled {
		return nil, nil
	}
	gate, err := quota.NewGate(cfg.Quota, keys, shared)
	if err != nil {
		return nil, err
	}
	return gate, nil
}

// gateConsult is the pre-dispatch back-pressure check: quota snapshot +
// schedule + system resources. A defer never marks the task processed, so
// the next scan reconsiders it (defer is throttle, not rejection); the
// (task, updated_on, reason) tuple is logged once per process to keep the
// JSONL free of per-scan spam.
func (c *Conductor) gateConsult(ctx context.Context, state *loopState, t task.Task) bool {
	if c.gate == nil && !c.resEnabled() {
		return true
	}
	if reasons := c.resourceReasons(); len(reasons) > 0 {
		c.logDefer(state, t, "resources busy: "+strings.Join(reasons, "; "))
		return false
	}
	if c.gate == nil {
		return true
	}
	d := c.gate.Decide(ctx, t.Class)
	if d.Action == quota.ActionDefer {
		c.logDefer(state, t, d.Reason)
		return false
	}
	return true
}

// resourceReasons samples the host and returns threshold violations ([] =
// not busy, or the monitor is off/unreadable — read failures never defer).
func (c *Conductor) resourceReasons() []string {
	rc := c.cfg.Resources
	if !rc.Enabled {
		return nil
	}
	st := quota.ReadResourceStats(rc.ProcRoot, rc.SysRoot, c.cfg.WorkRoot)
	return quota.BusyCheck{
		MaxLoadAvg:        rc.MaxLoadAvg,
		MinMemAvailableMB: rc.MinMemAvailableMB,
		MinDiskFreeMB:     rc.MinDiskFreeMB,
		MaxIODelayPct:     rc.MaxIODelayPct,
	}.Evaluate(st)
}

func (c *Conductor) resEnabled() bool { return c.cfg.Resources.Enabled }

// logDefer records one defer event (deduped per task+reason in-process).
func (c *Conductor) logDefer(state *loopState, t task.Task, reason string) {
	key := t.ID + "|" + t.UpdatedOn + "|" + reason
	if c.deferLogged == nil {
		c.deferLogged = map[string]bool{}
	}
	if c.deferLogged[key] {
		return
	}
	c.deferLogged[key] = true
	_ = state.log(loopEvent{Type: evDefer, TaskID: t.ID, UpdatedOn: t.UpdatedOn, Subject: t.Subject, Detail: reason})
	fmt.Fprintf(c.out, "harness: loop: defer %s: %s (reconsidered next scan; never marked processed)\n", t.ID, reason)
}

// gateStatusLine is the startup/`quota status` one-liner.
func (c *Conductor) gateStatusLine(ctx context.Context) string {
	if c.gate == nil && !c.resEnabled() {
		return "off"
	}
	parts := []string{}
	if c.gate != nil {
		snap := c.gate.Snapshot(ctx)
		parts = append(parts, c.gate.StatusLine(snap))
	}
	if c.resEnabled() {
		st := quota.ReadResourceStats(c.cfg.Resources.ProcRoot, c.cfg.Resources.SysRoot, c.cfg.WorkRoot)
		parts = append(parts, fmt.Sprintf("load=%.2f memAvail=%.0fMB diskFree=%.0fMB", st.LoadAvg1m, st.MemAvailable, st.DiskFree))
	}
	return strings.Join(parts, " | ")
}

// usageRow is one line of the per-class usage accounting (feeds the
// per-instance Discourse usage reports).
type usageRow struct {
	Class            string  `json:"class"`
	Turns            int     `json:"turns"`
	PromptTokens     int     `json:"prompt_tokens"`
	CompletionTokens int     `json:"completion_tokens"`
	TotalTokens      int     `json:"total_tokens"`
	Credits          float64 `json:"credits"`
}

// UsageReport renders the per-class token+credit accounting table from a
// loop state dir (read-only; `harness quota status`).
func UsageReport(stateDir string) (string, error) {
	s, err := openLoopStateReadOnly(stateDir)
	if err != nil {
		return "", err
	}
	defer s.Close()
	return usageReport(s.usageRows()), nil
}

// GateStatusLine is the exported one-liner for `harness quota` output.
func (c *Conductor) GateStatusLine(ctx context.Context) string {
	return c.gateStatusLine(ctx)
}

// ResourceSample reads one host sample for the CLI (nil-safe when off).
func (c *Conductor) ResourceSample() (quota.ResourceStats, bool) {
	if !c.resEnabled() {
		return quota.ResourceStats{}, false
	}
	rc := c.cfg.Resources
	return quota.ReadResourceStats(rc.ProcRoot, rc.SysRoot, c.cfg.WorkRoot), true
}

// usageReport renders the accounting table from the loop state.
func usageReport(rows []usageRow) string {
	sort.Slice(rows, func(i, j int) bool { return rows[i].Class < rows[j].Class })
	var b strings.Builder
	fmt.Fprintf(&b, "%-14s %6s %12s %12s %12s %10s\n", "CLASS", "TURNS", "PROMPT", "COMPLETION", "TOTAL", "CREDITS")
	var tot usageRow
	for _, r := range rows {
		fmt.Fprintf(&b, "%-14s %6d %12d %12d %12d %10.2f\n", r.Class, r.Turns, r.PromptTokens, r.CompletionTokens, r.TotalTokens, r.Credits)
		tot.Turns += r.Turns
		tot.PromptTokens += r.PromptTokens
		tot.CompletionTokens += r.CompletionTokens
		tot.TotalTokens += r.TotalTokens
		tot.Credits += r.Credits
	}
	fmt.Fprintf(&b, "%-14s %6d %12d %12d %12d %10.2f\n", "TOTAL", tot.Turns, tot.PromptTokens, tot.CompletionTokens, tot.TotalTokens, tot.Credits)
	return b.String()
}