package templates

import (
	"bytes"
	"context"
	"fmt"
	"strings"
	"time"

	"vetting/internal/model"
	"vetting/internal/store"
)

// PipelineNode is one dot on the detail-page timeline. The template
// doesn't know stages from pre-stages — it just renders whatever the
// BuildPipeline helper produces, in order.
type PipelineNode struct {
	Name        string
	State       string // pending|running|passed|failed|skipped
	StartedAt   *time.Time
	CompletedAt *time.Time
}

// preStageOrder are the nodes that show before the first real stage.
// Derived from run.State rather than stage rows since we don't persist
// pre-stage timestamps.
var preStageOrder = []model.RunState{
	model.StateQueued,
	model.StateWaitingReboot,
	model.StateBooting,
}

// runStateRank returns how far along the state machine a run is, using
// a linear ranking across pre-stages, stage states, and terminals. Used
// by BuildPipeline to decide which pre-stage nodes are "past" (passed),
// "current" (running), or "pending".
func runStateRank(s model.RunState) int {
	order := []model.RunState{
		model.StateRegistered,
		model.StateQueued,
		model.StateWaitingReboot,
		model.StateBooting,
		model.StateInventoryCheck,
		model.StateFirmware,
		model.StateSpecValidate,
		model.StateSMART,
		model.StateCPUStress,
		model.StateStorage,
		model.StateNetwork,
		model.StateBurn,
		model.StateGPU,
		model.StatePSU,
		model.StateReporting,
		model.StateCompleted,
	}
	for i, v := range order {
		if v == s {
			return i
		}
	}
	return -1
}

// BuildPipeline projects (run, stages) into a linear slice of nodes
// covering the whole lifecycle: pre-stage → all 9 stage nodes →
// Completed. Every stage in store.DefaultStageOrder always appears,
// even if its row hasn't been seeded yet — those show as "pending"
// ghosts. This way a run stuck in WaitingWoL (stages unseeded until
// /claim) still shows the full pipeline ahead of it.
//
// When run == nil we emit a ghost timeline (everything pending) so a
// never-run host still shows what's coming.
func BuildPipeline(run *model.Run, stages []model.Stage) []PipelineNode {
	nodes := make([]PipelineNode, 0, len(preStageOrder)+len(store.DefaultStageOrder)+1)

	// --- pre-stage nodes ---
	for _, ps := range preStageOrder {
		n := PipelineNode{Name: string(ps), State: "pending"}
		if run != nil {
			switch {
			case run.State == model.StateFailedHolding || run.State == model.StateFailed:
				// If we failed before reaching a stage, a pre-stage may
				// still have been entered — keep the "past" rank logic.
				if runStateRank(ps) < runStateRank(firstStageState(run)) {
					n.State = "passed"
				}
			case run.State == ps:
				n.State = "running"
			case runStateRank(run.State) > runStateRank(ps):
				n.State = "passed"
			}
		}
		nodes = append(nodes, n)
	}

	// --- stage nodes ---
	// Iterate DefaultStageOrder, not the stages slice, so the list is
	// always the full 9 nodes. For each stage, prefer the persisted row
	// if it exists; otherwise synthesize a ghost whose state is derived
	// from run state (passed if we've advanced past this stage's
	// RunState, running if we're in it, skipped if a prior stage failed,
	// pending otherwise).
	stageByName := make(map[string]model.Stage, len(stages))
	for _, st := range stages {
		stageByName[st.Name] = st
	}
	failedBefore := false
	for _, name := range store.DefaultStageOrder {
		n := PipelineNode{Name: name}
		if st, ok := stageByName[name]; ok {
			n.StartedAt = st.StartedAt
			n.CompletedAt = st.CompletedAt
			switch {
			case failedBefore:
				n.State = "skipped"
			case st.State == model.StagePassed:
				n.State = "passed"
			case st.State == model.StageRunning:
				n.State = "running"
			case st.State == model.StageFailed:
				n.State = "failed"
				failedBefore = true
			case st.State == model.StageSkipped:
				n.State = "skipped"
			default:
				n.State = "pending"
			}
		} else {
			// Ghost: no row seeded yet. Derive from run state.
			n.State = ghostStageState(run, name, failedBefore)
		}
		nodes = append(nodes, n)
	}

	// --- terminal Completed node ---
	term := PipelineNode{Name: "Completed", State: "pending"}
	if run != nil && run.State == model.StateCompleted {
		term.State = "passed"
		term.CompletedAt = run.CompletedAt
	}
	nodes = append(nodes, term)

	return nodes
}

// ghostStageState derives a pipeline-node state for a stage with no DB
// row — either the run hasn't reached /claim yet (pre-seed) or the stage
// is simply later than the run's current state. Mirrors the seeded-row
// logic so a ghost node transitions through the same visual states as a
// real one.
func ghostStageState(run *model.Run, name string, failedBefore bool) string {
	if failedBefore {
		return "skipped"
	}
	if run == nil {
		return "pending"
	}
	// Failed/FailedHolding: anything past the failed stage is skipped.
	if run.State == model.StateFailed || run.State == model.StateFailedHolding {
		if run.FailedStage != "" {
			failedRank, ok1 := stageRank(run.FailedStage)
			myRank, ok2 := stageRank(name)
			if ok1 && ok2 && myRank > failedRank {
				return "skipped"
			}
		}
		return "pending"
	}
	stageState, ok := stageStateByName(name)
	if !ok {
		return "pending"
	}
	switch {
	case run.State == stageState:
		return "running"
	case runStateRank(run.State) > runStateRank(stageState):
		return "passed"
	}
	return "pending"
}

// stageRank returns the ordinal of a stage within DefaultStageOrder,
// used to decide which stages are "after" a failed stage.
func stageRank(name string) (int, bool) {
	for i, s := range store.DefaultStageOrder {
		if s == name {
			return i, true
		}
	}
	return -1, false
}

// firstStageState returns the stage-state the run was in when it failed,
// or the current state for runs still in-flight. Used only by the
// pre-stage "past" check to decide if a Booting node should render
// "passed" even after the run failed further along.
func firstStageState(run *model.Run) model.RunState {
	if run.FailedStage != "" {
		if s, ok := stageStateByName(run.FailedStage); ok {
			return s
		}
	}
	return run.State
}

// stageStateByName mirrors orchestrator.StateForStage without the
// import (templates can't see orchestrator).
func stageStateByName(name string) (model.RunState, bool) {
	m := map[string]model.RunState{
		"Inventory":    model.StateInventoryCheck,
		"Firmware":     model.StateFirmware,
		"SpecValidate": model.StateSpecValidate,
		"SMART":        model.StateSMART,
		"CPUStress":    model.StateCPUStress,
		"Storage":      model.StateStorage,
		"Network":      model.StateNetwork,
		"Burn":         model.StateBurn,
		"GPU":          model.StateGPU,
		"PSU":          model.StatePSU,
		"Reporting":    model.StateReporting,
	}
	s, ok := m[name]
	return s, ok
}

func stageDuration(n PipelineNode) string {
	if d := elapsed(n.StartedAt, n.CompletedAt); d >= 0 {
		return fmtElapsed(d, false)
	}
	return ""
}

// stageDisplayName turns the internal single-word state/stage identifier
// into a human-readable label by inserting spaces before interior capital
// letters. "WaitingReboot" → "Waiting Reboot", "SpecValidate" →
// "Spec Validate", "CPUStress" → "CPU Stress". The space lets the
// pipeline node wrap the label onto two lines on narrow layouts instead
// of forcing horizontal scroll — single-word names ("Inventory",
// "Completed") pass through unchanged.
func stageDisplayName(name string) string {
	var b strings.Builder
	b.Grow(len(name) + 2)
	for i, r := range name {
		if i > 0 && r >= 'A' && r <= 'Z' {
			prev := rune(name[i-1])
			// Insert a space at every lower→upper boundary ("Spec|Validate")
			// and at upper→upper when the next char is lower ("CPU|Stress",
			// where we split before the S that starts a new word). This
			// keeps acronyms like "GPU"/"PSU" intact.
			if (prev >= 'a' && prev <= 'z') ||
				(prev >= 'A' && prev <= 'Z' && i+1 < len(name) && name[i+1] >= 'a' && name[i+1] <= 'z') {
				b.WriteByte(' ')
			}
		}
		b.WriteRune(r)
	}
	return b.String()
}

// stageMarker returns the single-char glyph shown in the node's dot.
// Dots stay colored-via-class; the glyph is redundant-but-helpful.
func stageMarker(state string) string {
	switch state {
	case "passed":
		return "✓"
	case "failed":
		return "!"
	case "running":
		return "●"
	case "skipped":
		return "–"
	}
	return ""
}

// Pipeline renders the ordered dot-and-line timeline. The caller wraps
// it in a <section id="pipeline-{runID}" sse-swap=...> so the runner can
// re-emit the fragment as stages progress.
templ Pipeline(nodes []PipelineNode) {
	<div class="pipeline">
		for i, n := range nodes {
			if i > 0 {
				<div class={ "stage-connector", "stage-connector-" + nodes[i-1].State }></div>
			}
			<div class={ "stage-node", "stage-node-" + n.State }>
				<div class={ "stage-dot", "stage-dot-" + n.State }>{ stageMarker(n.State) }</div>
				<div class="stage-name">{ stageDisplayName(n.Name) }</div>
				<div class="stage-duration">{ stageDuration(n) }</div>
			</div>
		}
	</div>
}

// PipelineSection wraps Pipeline in the same <section id=pipeline-N
// sse-swap=pipeline-N hx-swap=outerHTML> the runner targets. Used both
// from the initial detail-page shell and from RenderPipelineString so
// the wrapper is present on the wire and after every SSE swap — without
// this, the first outerHTML swap would replace the section with a bare
// <div class=pipeline>, wiping out the sse-swap attribute and freezing
// the pipeline until full page reload.
templ PipelineSection(run *model.Run, nodes []PipelineNode) {
	<section
		id={ fmt.Sprintf("pipeline-%d", run.ID) }
		class="detail-section"
		sse-swap={ fmt.Sprintf("pipeline-%d", run.ID) }
		hx-swap="outerHTML"
	>
		<h2>Pipeline</h2>
		@Pipeline(nodes)
	</section>
}

// RenderPipelineString is the one-shot renderer the orchestrator
// registers at startup so it can publish pipeline fragments over SSE
// without pulling in the template package directly. Returns the full
// PipelineSection wrapper so repeat outerHTML swaps preserve the
// sse-swap target.
func RenderPipelineString(run *model.Run, stages []model.Stage) string {
	if run == nil {
		return ""
	}
	var buf bytes.Buffer
	_ = PipelineSection(run, BuildPipeline(run, stages)).Render(context.Background(), &buf)
	return buf.String()
}