// SPDX-License-Identifier: EUPL-1.2

package agentic

import (
	"strconv"
	"syscall"
	"time"

	core "dappco.re/go/core"
	"gopkg.in/yaml.v3"
)

// DispatchConfig controls agent dispatch behaviour.
//
//	cfg := agentic.DispatchConfig{DefaultAgent: "claude", DefaultTemplate: "coding"}
type DispatchConfig struct {
	DefaultAgent    string `yaml:"default_agent"`
	DefaultTemplate string `yaml:"default_template"`
	WorkspaceRoot   string `yaml:"workspace_root"`
}

// RateConfig controls pacing between task dispatches.
//
//	rate := agentic.RateConfig{ResetUTC: "06:00", SustainedDelay: 120, BurstWindow: 2, BurstDelay: 15}
type RateConfig struct {
	ResetUTC       string `yaml:"reset_utc"`       // Daily quota reset time (UTC), e.g. "06:00"
	DailyLimit     int    `yaml:"daily_limit"`     // Max requests per day (0 = unknown)
	MinDelay       int    `yaml:"min_delay"`       // Minimum seconds between task starts
	SustainedDelay int    `yaml:"sustained_delay"` // Delay when pacing for full-day use
	BurstWindow    int    `yaml:"burst_window"`    // Hours before reset where burst kicks in
	BurstDelay     int    `yaml:"burst_delay"`     // Delay during burst window
}

// AgentsConfig is the root of config/agents.yaml.
//
//	cfg := agentic.AgentsConfig{Version: 1, Dispatch: agentic.DispatchConfig{DefaultAgent: "claude"}}
type AgentsConfig struct {
	Version     int                   `yaml:"version"`
	Dispatch    DispatchConfig        `yaml:"dispatch"`
	Concurrency map[string]int        `yaml:"concurrency"`
	Rates       map[string]RateConfig `yaml:"rates"`
}

// loadAgentsConfig reads config/agents.yaml from the code path.
func (s *PrepSubsystem) loadAgentsConfig() *AgentsConfig {
	paths := []string{
		core.JoinPath(CoreRoot(), "agents.yaml"),
		core.JoinPath(s.codePath, "core", "agent", "config", "agents.yaml"),
	}

	for _, path := range paths {
		r := fs.Read(path)
		if !r.OK {
			continue
		}
		var cfg AgentsConfig
		if err := yaml.Unmarshal([]byte(r.Value.(string)), &cfg); err != nil {
			continue
		}
		return &cfg
	}

	return &AgentsConfig{
		Dispatch: DispatchConfig{
			DefaultAgent:    "claude",
			DefaultTemplate: "coding",
		},
		Concurrency: map[string]int{
			"claude": 1,
			"gemini": 3,
		},
	}
}

// delayForAgent calculates how long to wait before spawning the next task
// for a given agent type, based on rate config and time of day.
func (s *PrepSubsystem) delayForAgent(agent string) time.Duration {
	cfg := s.loadAgentsConfig()
	// Strip variant suffix (claude:opus → claude) for config lookup
	base := baseAgent(agent)
	rate, ok := cfg.Rates[base]
	if !ok || rate.SustainedDelay == 0 {
		return 0
	}

	// Parse reset time
	resetHour, resetMin := 6, 0
	parts := core.Split(rate.ResetUTC, ":")
	if len(parts) >= 2 {
		if hour, err := strconv.Atoi(core.Trim(parts[0])); err == nil {
			resetHour = hour
		}
		if min, err := strconv.Atoi(core.Trim(parts[1])); err == nil {
			resetMin = min
		}
	}

	now := time.Now().UTC()
	resetToday := time.Date(now.Year(), now.Month(), now.Day(), resetHour, resetMin, 0, 0, time.UTC)
	if now.Before(resetToday) {
		// Reset hasn't happened yet today — reset was yesterday
		resetToday = resetToday.AddDate(0, 0, -1)
	}
	nextReset := resetToday.AddDate(0, 0, 1)
	hoursUntilReset := nextReset.Sub(now).Hours()

	// Burst mode: if within burst window of reset, use burst delay
	if rate.BurstWindow > 0 && hoursUntilReset <= float64(rate.BurstWindow) {
		return time.Duration(rate.BurstDelay) * time.Second
	}

	// Sustained mode
	return time.Duration(rate.SustainedDelay) * time.Second
}

// countRunningByAgent counts running workspaces for a specific agent type.
// Scans both old (*/status.json) and new (*/*/*/status.json) workspace layouts.
func (s *PrepSubsystem) countRunningByAgent(agent string) int {
	wsRoot := WorkspaceRoot()

	// Scan both old and new workspace layouts
	old := core.PathGlob(core.JoinPath(wsRoot, "*", "status.json"))
	new := core.PathGlob(core.JoinPath(wsRoot, "*", "*", "*", "status.json"))
	paths := append(old, new...)

	count := 0
	for _, statusPath := range paths {
		st, err := readStatus(core.PathDir(statusPath))
		if err != nil || st.Status != "running" {
			continue
		}
		if baseAgent(st.Agent) != agent {
			continue
		}

		if st.PID > 0 && syscall.Kill(st.PID, 0) == nil {
			count++
		}
	}

	return count
}

// baseAgent strips the model variant (gemini:flash → gemini).
func baseAgent(agent string) string {
	// codex:gpt-5.3-codex-spark → codex-spark (separate pool)
	if core.Contains(agent, "codex-spark") {
		return "codex-spark"
	}
	return core.SplitN(agent, ":", 2)[0]
}

// canDispatchAgent checks if we're under the concurrency limit for a specific agent type.
func (s *PrepSubsystem) canDispatchAgent(agent string) bool {
	cfg := s.loadAgentsConfig()
	base := baseAgent(agent)
	limit, ok := cfg.Concurrency[base]
	if !ok || limit <= 0 {
		return true
	}
	return s.countRunningByAgent(base) < limit
}

// drainQueue fills all available concurrency slots from queued workspaces.
// Loops until no slots remain or no queued tasks match. Serialised via drainMu.
func (s *PrepSubsystem) drainQueue() {
	if s.frozen {
		return
	}
	s.drainMu.Lock()
	defer s.drainMu.Unlock()

	for s.drainOne() {
		// keep filling slots
	}
}

// drainOne finds the oldest queued workspace and spawns it if a slot is available.
// Returns true if a task was spawned, false if nothing to do.
func (s *PrepSubsystem) drainOne() bool {
	wsRoot := WorkspaceRoot()

	// Scan both old and new workspace layouts
	old := core.PathGlob(core.JoinPath(wsRoot, "*", "status.json"))
	deep := core.PathGlob(core.JoinPath(wsRoot, "*", "*", "*", "status.json"))
	statusFiles := append(old, deep...)

	for _, statusPath := range statusFiles {
		wsDir := core.PathDir(statusPath)
		st, err := readStatus(wsDir)
		if err != nil || st.Status != "queued" {
			continue
		}

		if !s.canDispatchAgent(st.Agent) {
			continue
		}

		// Skip if agent pool is in rate-limit backoff
		pool := baseAgent(st.Agent)
		if until, ok := s.backoff[pool]; ok && time.Now().Before(until) {
			continue
		}

		// Apply rate delay before spawning
		delay := s.delayForAgent(st.Agent)
		if delay > 0 {
			time.Sleep(delay)
		}

		// Re-check concurrency after delay (another task may have started)
		if !s.canDispatchAgent(st.Agent) {
			continue
		}

		prompt := "TASK: " + st.Task + "\n\nResume from where you left off. Read CODEX.md for conventions. Commit when done."

		pid, _, err := s.spawnAgent(st.Agent, prompt, wsDir)
		if err != nil {
			continue
		}

		st.Status = "running"
		st.PID = pid
		st.Runs++
		writeStatus(wsDir, st)

		return true
	}

	return false
}