/******************************************************************************
               __               ____                __
              / /   ___  ____ _/ __/_____________ _/ /__
             / /   / _ \/ __ `/ /_/ ___/ ___/ __ `/ / _ \
            / /___/  __/ /_/ / __(__  ) /__/ /_/ / /  __/
           /_____/\___/\__,_/_/ /____/\___/\__,_/_/\___/

   (C)opyright 2025, Leafscale, LLC -  https://www.leafscale.com

   Project: Zygaena
  Filename: version.reef
   Authors: Chris Tusa <chris.tusa@leafscale.com>
   License: <see LICENSE file included with this source code>
Description: Semantic version parsing and comparison utilities

******************************************************************************/

module util.version

import core.str

export
    // Version constraint parsing
    type DepConstraint

    // Compare two version strings semantically
    // Returns: -1 if v1 < v2, 0 if v1 == v2, 1 if v1 > v2
    fn compare_versions(v1: string, v2: string): int

    // Check if v1 is newer than v2
    fn is_newer(v1: string, v2: string): bool

    // Parse a dependency string with optional version constraint
    // e.g., "libfoo>=1.0" -> { name: "libfoo", op: ">=", version: "1.0" }
    fn parse_dep_constraint(dep: string): DepConstraint

    // Check if an installed version satisfies a version constraint
    fn check_version_constraint(installed_version: string, op: string, required_version: string): bool

    // Accessor functions for DepConstraint
    fn constraint_name(c: DepConstraint): string
    fn constraint_op(c: DepConstraint): string
    fn constraint_version(c: DepConstraint): string
    fn has_constraint(c: DepConstraint): bool

    // Extract version from package filename
    // e.g., "reef-0.1.10-1.pkg.tar.xz" -> "0.1.10"
    fn extract_version_from_filename(filename: string, pkg_name: string): string

    // Extract release number from package filename
    // e.g., "reef-0.1.10-1.pkg.tar.xz" -> 1
    fn extract_release_from_filename(filename: string): int
end export

// Parsed dependency constraint
type DepConstraint = struct
    name: string
    op: string
    version: string
end DepConstraint

// Compare two version strings semantically
// Handles versions like "0.1.10" vs "0.1.7" correctly (0.1.10 > 0.1.7)
fn compare_versions(v1: string, v2: string): int
    // Parse version components
    mut v1_parts: [int] = new [int](10)
    mut v2_parts: [int] = new [int](10)

    let v1_count = parse_version(v1, v1_parts, 10)
    let v2_count = parse_version(v2, v2_parts, 10)

    // Compare each component
    let max_parts = max_int(v1_count, v2_count)

    mut i = 0
    while i < max_parts
        let p1 = get_part(v1_parts, v1_count, i)
        let p2 = get_part(v2_parts, v2_count, i)

        if p1 > p2
            return 1
        elif p1 < p2
            return -1
        end if

        i = i + 1
    end while

    return 0
end compare_versions

// Check if v1 is newer than v2
fn is_newer(v1: string, v2: string): bool
    return compare_versions(v1, v2) > 0
end is_newer

// Parse version string into integer components
// "0.1.10" -> [0, 1, 10]
fn parse_version(version: string, parts: [int], max_parts: int): int
    mut count = 0
    mut current = 0
    mut in_number = false

    mut i = 0
    while i < str.length(version) and count < max_parts
        let c = str.char_at(version, i)

        if is_digit(c)
            current = current * 10 + char_to_digit(c)
            in_number = true
        elif c == '.' or c == '-'
            if in_number
                parts[count] = current
                count = count + 1
                current = 0
                in_number = false
            end if
        else
            // Skip non-numeric characters (like 'alpha', 'beta', 'rc')
            if in_number
                parts[count] = current
                count = count + 1
                current = 0
                in_number = false
            end if
        end if

        i = i + 1
    end while

    // Don't forget the last number
    if in_number and count < max_parts
        parts[count] = current
        count = count + 1
    end if

    return count
end parse_version

// Extract version from package filename
// e.g., "reef-0.1.10-1.pkg.tar.xz" with pkg_name "reef" -> "0.1.10"
fn extract_version_from_filename(filename: string, pkg_name: string): string
    // Remove package name prefix and dash
    let prefix_len = str.length(pkg_name) + 1

    if str.length(filename) <= prefix_len
        return ""
    end if

    // Get the part after "pkgname-"
    let rest = str.substring(filename, prefix_len, str.length(filename) - prefix_len)

    // Find the last dash before .pkg.tar.xz (that's the release separator)
    // e.g., "0.1.10-1.pkg.tar.xz" -> version is "0.1.10"
    let suffix = ".pkg.tar.xz"
    let suffix_len = str.length(suffix)

    if not str.ends_with(rest, suffix)
        return ""
    end if

    // Remove suffix: "0.1.10-1.pkg.tar.xz" -> "0.1.10-1"
    let ver_rel = str.substring(rest, 0, str.length(rest) - suffix_len)

    // Find last dash (release separator)
    let last_dash = str.last_index_of_char(ver_rel, '-')
    if last_dash < 0
        return ver_rel
    end if

    // Return version part: "0.1.10-1" -> "0.1.10"
    return str.substring(ver_rel, 0, last_dash)
end extract_version_from_filename

// Extract release number from package filename
// e.g., "reef-0.1.10-1.pkg.tar.xz" -> 1
fn extract_release_from_filename(filename: string): int
    let suffix = ".pkg.tar.xz"

    if not str.ends_with(filename, suffix)
        return 1
    end if

    // Remove suffix
    let without_suffix = str.substring(filename, 0, str.length(filename) - str.length(suffix))

    // Find last dash
    let last_dash = str.last_index_of_char(without_suffix, '-')
    if last_dash < 0
        return 1
    end if

    // Extract release number
    let release_str = str.substring(without_suffix, last_dash + 1, str.length(without_suffix) - last_dash - 1)

    return parse_int(release_str)
end extract_release_from_filename

// Helper: check if character is a digit
fn is_digit(c: char): bool
    return c >= '0' and c <= '9'
end is_digit

// Helper: convert digit character to integer
fn char_to_digit(c: char): int
    return c - '0'
end char_to_digit

// Helper: get part at index, or 0 if out of bounds
fn get_part(parts: [int], count: int, idx: int): int
    if idx < count
        return parts[idx]
    end if
    return 0
end get_part

// Helper: max of two integers
fn max_int(a: int, b: int): int
    if a > b
        return a
    end if
    return b
end max_int

// Helper: parse string to int
fn parse_int(s: string): int
    mut result = 0
    mut i = 0
    while i < str.length(s)
        let c = str.char_at(s, i)
        if is_digit(c)
            result = result * 10 + char_to_digit(c)
        else
            break
        end if
        i = i + 1
    end while
    return result
end parse_int

// Parse a dependency string into name, operator, and version
// Handles: "libfoo", "libfoo>=1.0", "libfoo<=2.0", "libfoo>1.0", "libfoo<2.0", "libfoo=1.0"
fn parse_dep_constraint(dep: string): DepConstraint
    let len = str.length(dep)

    mut i = 0
    while i < len
        let c = str.char_at(dep, i)

        if c == '>' or c == '<' or c == '='
            let name = str.substring(dep, 0, i)

            // Check for two-char operators (>=, <=)
            if i + 1 < len
                let next = str.char_at(dep, i + 1)
                if next == '='
                    let op = str.substring(dep, i, 2)
                    let ver = str.substring(dep, i + 2, len - i - 2)
                    return DepConstraint{ name: name, op: op, version: ver }
                end if
            end if

            // Single char operator (>, <, =)
            let op = str.substring(dep, i, 1)
            let ver = str.substring(dep, i + 1, len - i - 1)
            return DepConstraint{ name: name, op: op, version: ver }
        end if

        i = i + 1
    end while

    // No constraint
    return DepConstraint{ name: dep, op: "", version: "" }
end parse_dep_constraint

// Check if an installed version satisfies a version constraint
fn check_version_constraint(installed_version: string, op: string, required_version: string): bool
    if str.length(op) == 0
        return true
    end if

    let cmp = compare_versions(installed_version, required_version)

    if str.equals(op, ">=")
        return cmp >= 0
    elif str.equals(op, "<=")
        return cmp <= 0
    elif str.equals(op, ">")
        return cmp > 0
    elif str.equals(op, "<")
        return cmp < 0
    elif str.equals(op, "=")
        return cmp == 0
    end if

    return true
end check_version_constraint

// Accessor functions
fn constraint_name(c: DepConstraint): string
    return c.name
end constraint_name

fn constraint_op(c: DepConstraint): string
    return c.op
end constraint_op

fn constraint_version(c: DepConstraint): string
    return c.version
end constraint_version

fn has_constraint(c: DepConstraint): bool
    return str.length(c.op) > 0
end has_constraint

end module