package main

// A design as the progress verb reads it (novox/hq issue 1947): its title, its state as its frontmatter says it and
// the decisions it names, read through the records module until ADR 0423 makes designs records of the knowledge base
// (issue 428). Its milestones are the issue tracker's records (ADR 0493 §1, issue 1781), read in milestones.go: the
// table parse that guessed them from prose moved to the tracker's seed and is gone from here.

import (
	"fmt"
	"regexp"
	"sort"
	"strconv"
	"strings"
)

// DesignsFolder is where the designs being built are, in hq.
const DesignsFolder = "03-DESIGN/01-to-be"

// Design is one design as read.
type Design struct {
	Number     int
	Path       string
	Title      string
	Status     string
	Decisions  []string
	Milestones []Milestone
}

// Milestone is one milestone of a design, as the issue tracker keeps it.
type Milestone struct {
	ID      string
	Outcome string
	Issues  []int
	// Status is open or closed, with its Reason; a closed milestone holding no issue is done.
	Status string
	Reason string
	// Moved is who last moved it and when, as the tracker says it; nil before its first move.
	Moved *stamp
}

var (
	designFile   = regexp.MustCompile(`^([0-9]{2,3})-[a-z0-9-]+\.md$`)
	titleLine    = regexp.MustCompile(`^#\s+[0-9]+\s+[—-]\s+(.+)$`)
	decisionItem = regexp.MustCompile(`ADR ([0-9]{4})`)
)

// parseDesign reads a design document.
func parseDesign(path, content string) *Design {
	d := &Design{Path: path}
	if m := designFile.FindStringSubmatch(lastPart(path)); m != nil {
		d.Number, _ = strconv.Atoi(m[1])
	}
	lines := strings.Split(content, "\n")
	body := 0
	if len(lines) > 0 && strings.TrimSpace(lines[0]) == "---" {
		for i := 1; i < len(lines); i++ {
			l := lines[i]
			if strings.TrimSpace(l) == "---" {
				body = i + 1
				break
			}
			if v, ok := strings.CutPrefix(l, "status:"); ok {
				d.Status = strings.TrimSpace(v)
			}
			for _, m := range decisionItem.FindAllStringSubmatch(l, -1) {
				d.Decisions = append(d.Decisions, "ADR "+m[1])
			}
		}
	}
	for i := body; i < len(lines) && d.Title == ""; i++ {
		if m := titleLine.FindStringSubmatch(strings.TrimSpace(lines[i])); m != nil {
			d.Title = strings.TrimSpace(m[1])
		}
	}
	return d
}

func lastPart(p string) string {
	if i := strings.LastIndex(p, "/"); i >= 0 {
		return p[i+1:]
	}
	return p
}

// milestone finds a milestone by its id, without regard to case, or to spaces against hyphens.
func (d *Design) milestone(id string) *Milestone {
	// The tracker keeps an id's words joined by hyphens (3 fix is 3-fix); either is taken.
	want := strings.ToLower(strings.Join(strings.Fields(id), "-"))
	for i := range d.Milestones {
		if strings.ToLower(strings.Join(strings.Fields(d.Milestones[i].ID), "-")) == want {
			return &d.Milestones[i]
		}
	}
	return nil
}

// issues is every issue its milestones name, each once, in order.
func (d *Design) issues() []int {
	var out []int
	have := map[int]bool{}
	for _, m := range d.Milestones {
		for _, n := range m.Issues {
			if !have[n] {
				have[n] = true
				out = append(out, n)
			}
		}
	}
	return out
}

// designsCache is the designs read at one commit of hq: read again only when the records module's checkout moves.
type designsCache struct {
	commit string
	paths  []string
	byPath map[string]*Design
}

// designs answers the designs being built, read at the commit the records module stands at, from the cache while
// that commit stands (novox/hq issue 1947, 1947/AC6).
func (k *KB) designs(all bool, number int) ([]*Design, string, error) {
	if k.Records == nil {
		return nil, "", fmt.Errorf("the knowledge base reads no records here")
	}
	commit, err := k.Records.Standing()
	if err != nil {
		return nil, "", fmt.Errorf("the records module does not say where hq stands: %v", err)
	}
	k.progMu.Lock()
	defer k.progMu.Unlock()
	c := k.progCache
	if c == nil || c.commit != commit {
		c = &designsCache{commit: commit, byPath: map[string]*Design{}}
		_, docs, err := k.Records.List(DesignsFolder)
		if err != nil {
			return nil, "", fmt.Errorf("the records module does not list %s: %v", DesignsFolder, err)
		}
		for _, doc := range docs {
			if designFile.MatchString(doc) {
				c.paths = append(c.paths, DesignsFolder+"/"+doc)
			}
		}
		sort.Strings(c.paths)
		k.progCache = c
	}
	var out []*Design
	for _, p := range c.paths {
		n, _ := strconv.Atoi(designFile.FindStringSubmatch(lastPart(p))[1])
		if !all && n != number {
			continue
		}
		d := c.byPath[p]
		if d == nil {
			content, _, err := k.Records.Read(p)
			if err != nil {
				return nil, "", fmt.Errorf("the records module does not read %s: %v", p, err)
			}
			d = parseDesign(p, content)
			c.byPath[p] = d
			k.progReads++
		}
		out = append(out, d)
	}
	if !all && len(out) == 0 {
		return nil, "", fmt.Errorf("no design %d is in %s at hq %s", number, DesignsFolder, short(commit))
	}
	return out, commit, nil
}