// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Package cover provides support for parsing coverage profiles
// generated by "go test -coverprofile=cover.out".
package cover

import (
	"bufio"
	"fmt"
	"math"
	"os"
	"regexp"
	"sort"
	"strconv"
	"strings"
)

// Profile represents the profiling data for a specific file.
type Profile struct {
	FileName string
	Mode     string
	Blocks   []ProfileBlock
}

// ProfileBlock represents a single block of profiling data.
type ProfileBlock struct {
	StartLine, StartCol int
	EndLine, EndCol     int
	NumStmt, Count      int
}

type byFileName []*Profile

func (p byFileName) Len() int           { return len(p) }
func (p byFileName) Less(i, j int) bool { return p[i].FileName < p[j].FileName }
func (p byFileName) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }

// ParseProfiles parses profile data in the specified file and returns a
// Profile for each source file described therein.
func ParseProfiles(fileName string) ([]*Profile, error) {
	pf, err := os.Open(fileName)
	if err != nil {
		return nil, err
	}
	defer pf.Close()

	files := make(map[string]*Profile)
	buf := bufio.NewReader(pf)
	// First line is "mode: foo", where foo is "set", "count", or "atomic".
	// Rest of file is in the format
	//	encoding/base64/base64.go:34.44,37.40 3 1
	// where the fields are: name.go:line.column,line.column numberOfStatements count
	s := bufio.NewScanner(buf)
	mode := ""
	for s.Scan() {
		line := s.Text()
		if mode == "" {
			const p = "mode: "
			if !strings.HasPrefix(line, p) || line == p {
				return nil, fmt.Errorf("bad mode line: %v", line)
			}
			mode = line[len(p):]
			continue
		}
		m := lineRe.FindStringSubmatch(line)
		if m == nil {
			return nil, fmt.Errorf("line %q doesn't match expected format: %v", m, lineRe)
		}
		fn := m[1]
		p := files[fn]
		if p == nil {
			p = &Profile{
				FileName: fn,
				Mode:     mode,
			}
			files[fn] = p
		}
		p.Blocks = append(p.Blocks, ProfileBlock{
			StartLine: toInt(m[2]),
			StartCol:  toInt(m[3]),
			EndLine:   toInt(m[4]),
			EndCol:    toInt(m[5]),
			NumStmt:   toInt(m[6]),
			Count:     toInt(m[7]),
		})
	}
	if err := s.Err(); err != nil {
		return nil, err
	}
	for _, p := range files {
		sort.Sort(blocksByStart(p.Blocks))
	}
	// Generate a sorted slice.
	profiles := make([]*Profile, 0, len(files))
	for _, profile := range files {
		profiles = append(profiles, profile)
	}
	sort.Sort(byFileName(profiles))
	return profiles, nil
}

type blocksByStart []ProfileBlock

func (b blocksByStart) Len() int      { return len(b) }
func (b blocksByStart) Swap(i, j int) { b[i], b[j] = b[j], b[i] }
func (b blocksByStart) Less(i, j int) bool {
	bi, bj := b[i], b[j]
	return bi.StartLine < bj.StartLine || bi.StartLine == bj.StartLine && bi.StartCol < bj.StartCol
}

var lineRe = regexp.MustCompile(`^(.+):([0-9]+).([0-9]+),([0-9]+).([0-9]+) ([0-9]+) ([0-9]+)$`)

func toInt(s string) int {
	i, err := strconv.Atoi(s)
	if err != nil {
		panic(err)
	}
	return i
}

// Boundary represents the position in a source file of the beginning or end of a
// block as reported by the coverage profile. In HTML mode, it will correspond to
// the opening or closing of a <span> tag and will be used to colorize the source
type Boundary struct {
	Offset int     // Location as a byte offset in the source file.
	Start  bool    // Is this the start of a block?
	Count  int     // Event count from the cover profile.
	Norm   float64 // Count normalized to [0..1].
}

// Boundaries returns a Profile as a set of Boundary objects within the provided src.
func (p *Profile) Boundaries(src []byte) (boundaries []Boundary) {
	// Find maximum count.
	max := 0
	for _, b := range p.Blocks {
		if b.Count > max {
			max = b.Count
		}
	}
	// Divisor for normalization.
	divisor := math.Log(float64(max))

	// boundary returns a Boundary, populating the Norm field with a normalized Count.
	boundary := func(offset int, start bool, count int) Boundary {
		b := Boundary{Offset: offset, Start: start, Count: count}
		if !start || count == 0 {
			return b
		}
		if max <= 1 {
			b.Norm = 0.8 // Profile is in"set" mode; we want a heat map. Use cov8 in the CSS.
		} else if count > 0 {
			b.Norm = math.Log(float64(count)) / divisor
		}
		return b
	}

	line, col := 1, 2 // TODO: Why is this 2?
	for si, bi := 0, 0; si < len(src) && bi < len(p.Blocks); {
		b := p.Blocks[bi]
		if b.StartLine == line && b.StartCol == col {
			boundaries = append(boundaries, boundary(si, true, b.Count))
		}
		if b.EndLine == line && b.EndCol == col {
			boundaries = append(boundaries, boundary(si, false, 0))
			bi++
			continue // Don't advance through src; maybe the next block starts here.
		}
		if src[si] == '\n' {
			line++
			col = 0
		}
		col++
		si++
	}
	sort.Sort(boundariesByPos(boundaries))
	return
}

type boundariesByPos []Boundary

func (b boundariesByPos) Len() int      { return len(b) }
func (b boundariesByPos) Swap(i, j int) { b[i], b[j] = b[j], b[i] }
func (b boundariesByPos) Less(i, j int) bool {
	if b[i].Offset == b[j].Offset {
		return !b[i].Start && b[j].Start
	}
	return b[i].Offset < b[j].Offset
}